I need 3000 Hz Output sampling in MCUs  - Page 1
Forum section: electronics / general

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 12:11:38 am
content: Hi,I need to build an equipment similar to EMG but not exactly an EMG, the equipment need the same 10mV output but I need the frequency to be up to 1000 Hz (instead of just 50 Hz to 150 Hz or 300 Hz typical in EMG)The Nyquist frequency is twice the frequency of the highest frequency one wants to digitize. Therefore a sampling frequency of 3000 Hz will be required for the equipment since 3000 Hz is more than twice 1000 Hz for superb sampling.My only experience was with the Motorola 68HC11. It takes 16 micro seconds to read one register in the ADC buffer. However, it's real time interrupt vector is 4ms fastest. And with only RS-232 serial output that is 10000 times slower than a USB. I can't get a signal that is even better than 250 Hz. The computation is 1/ 4m(RTI) = 250 so 250 Hz is the best it can output, however considering that a serial port is much slower, the frequency is like 100 Hz only.I am on hand an EEG device based on the Texas Instrument MSP430F2617 which I'm studying. It was made to output EEG signal in microVolt and 0 to 60 Hz only. But I think I can adjust it to make it output in millivolts. But I'm still figuring out the maximum frequency the hardware is really capable of. How do I compute the maximum frequency the device can output? The msp430 manual is too long and so I need someone familiar with the MSP430 to share some answers.In your computation, can an MSP430F2617 output 3000 Hz signal? Or since the chip uses serial port, then the weak link is the serial port, right? But as the MSP430 is much faster than the Motorola 68Hc11. Is the MSP430 serial ports much faster too enough to do a 3000 Hz output.The above consider 2 separate cases. One is the msp430 using its own 12 bit ADC. However in the EEG equipment I have. It has a 24 bit ADC right after the vac1 op-amp connected to the brain electrodes as shown in the following:Do you think it can produce a 3000 Hz output? But the problem is it is connected to the MSP430F2617 with its build in serial port connected to the USB via the FTDI FT232BM chip. Theoretically it still ouputs in serial speed, right?I plan to just rewrite its firmware to adjust the frequency. Do you think other MCU with built in USB would be much faster than it versus this one with serial port and needing an external serial to USB converter. Or do other MCUs also have serial to USB converter built within the MCU chip Then it will be slow as well.Thank you.

author: ataradov
author_rank: Super Contributor
timestamp: January 15, 2023, 12:54:08 am
content: There is a lot of stuff mixed in here. Sampling ADC at 3 kHz is certainly possible with any modern MCU. Generating 3 kHz is also trivial. But what this has to do with serial port at all? And what is connected with a serial port?I think you need to better describe the problem and what other parameters of the signal you need to achieve. Like duty cycle or duration.And don't assume we know what EMG or EEG are and what are the requirements for them.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 01:05:56 am
content: Yeah, something like a STM32F4 can sample at over 1,000,000 samples/sec at 12bit.and a ATMega328 can do around 15,000 at 8bitSo your sample rate requirement isn't an issue.Of course, depending on what you are doing with the sample, you need to have the CPU speed to finish processing a sample before the next one arrives.There is also cost to consider, a high end MCUs may have everything you need built-in but cost may remove it from consideration?.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 01:14:49 am
content: EEG measures brain waves at 0 to 50 Hz in 0 to 200 microvolts rangeEMG measure muscle waves at 50 Hz to 30 Hz in 0 to 10millivolts rangeI want to create a device that can measure EMG up to 1000 Hz.I have an existing EEG that I plan to modify in the firmware only. It has a MSP430F2167 chip on it. It is connected to the FDTI FT232BM (serial to USB converter) with the following specs.https://www.ftdichip.com/old2020/Products/ICs/FT232BM.htm"Single chip USB <=> asynchronous serial data transferFull handshaking & modem interface signalsUART interface supports 7/8 data bits, 1/2 stop bits and Odd/Even/Mark/Space/No ParityData transfer rate of 300 Baud => 3M Baud (TTL)Data transfer rate of 300 Baud => 1M Baud (RS232)Data transfer rate of 300 Baud => 3M Baud (RS422/RS485)384 Byte Rx buffer/128 Byte Tx buffer for high data throughputAdjustable Rx buffer timeoutFully assisted hardware or X-On/X-Off handshakingBuilt-in support for event characters and line break conditionAuto transmit buffer control for RS485Support for USB suspend/resume through SLEEP# and RI# pinsSupport for high power USB bus powered devices through PWREN# pinIntegrated level converter on UART and control signals for interfacing to 5V and 3.3V logicIntegrated 3.3V regulator for USB IOIntegrated Power-On-Reset circuitIntegrated 6MHz - 48Mhz clock multiplier PLLUSB Bulk or Isochronous data transfer modes4.35V to 5.25V single supply operationUHCI/OHCI/EHCI host controller compatibleUSB 1.1 and USB 2.0 compatibleUSB VID, PID, serial number and product description strings in external EEPROMEEPROM programmable on-board via USBCompact 32-LD LQFP or QFN-32 packageAvailable as a Lead-free device (FT232BL and FT232BQ) compliant to EU directive 2002/95/EG RoHS"Question. Is the above combination of MSP430F167 and FDTI FT232BM able to output 3000 Hz? Is it not serial port is very slow as it sends the bit one by bit and 10000 times slower than a USB?

author: ataradov
author_rank: Super Contributor
timestamp: January 15, 2023, 01:22:25 am
content: There is no need to copy paste data for FTDI chips. Unlike EMG or EEG most people here would know what they areMCU does not need any USB to output a frequency at all. That's why I'm asking if you have some special requirements for variable frequency, duty cycle, modulations? If this is just a fixed square wave, then what do you need USB for?Even the spec you have here ways that it can do up to 1M Baud on the serial port. That's fast enough for most things. If this was enough in the original application, it would be enough here.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 01:30:39 am
content: FT232R can do up to 3M Baud, though you are pushing it at 3M.So 3M bit / 10 (8bits + 1 stop + 1 parity) = 300,000 bytes per second (in reality less)From a quick skim of the DS the MSP430 USART can do baud of 1/3 of BRCLK which can be 1,048,576hz.So that would be 350kbaud. So 35,000 bytes / sec.Note you will have some overhead as you probably need to make a packet structure to include a descriptor byte that indicates what that data is, and maybe a CRC/checksum.But at 35,000 your packet could be 35,000 / 3000 = max 11 char long. (In reality probably less, maybe 8char).So seems ok for one stream at 3khz, you could have a UART packet 4 bytes long. header, type, data, checksum.And looks to be room to add a few more 3khz streams to the package before its too long.Assuming of course you have the CPU to process it quick enough.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 01:34:04 am
content: Let me clarify.The MCU outputs the EEG Data via USB and shows it up in say Teraterm terminal or any terminal even inside CSS.The EEG App just read the EEG Data via USB and terminal.However in my application. I need it to output via USB and Tera Term 3000 Hz. Can it do that? The EEG app can only accepts up to 256 Hz. I need to find app that can show waveforms up to 3000 Hz. But that's another day.Right now I just want to know if the Tera term can get 3000 Hz waveform data from the USB at all.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 01:38:22 am
content: Quote from: planc on January 15, 2023, 01:34:04 amTera term has nothing to do with USB, it thinks its a serial port because the FT232 driver is converting USB to serial.And yes, all serial ports and serial port terminal software like tera term can do 115k baud (maybe more but atleast 115k).So that would be 11,500 bytes per second.So you can send 3.8 bytes/s at 3000 hz (in theory)But when dealing with data that fast you aren't usually going to be using tera term because its scrolls so fast you can't do anything with it. Unless you save it to disk and review later. Normally you would code your own windows app to read the data and generate a graph or something.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 01:48:21 am
content: Of course I need a PC app that can show the USB output in waveforms and can also filter 700Hz , 800 Hz, 1000 Hz in the screen.But first I need to know if the MSP430F2617 with serial pins can even output 3000 Hz to the FT232 chip.The 68HC11 I had experience with just couldn't. Could the above MSP430F2617 do it?

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 01:54:33 am
content: 99.99% of MCUs can do 115200 baud because no one would buy them if they couldn't.It's a standard board rate, and most can go a little higher, sometimes up to 1M or even 3M.So yes, the MSP430F2617 can do 115200 baud / 11.5kbyte/s.(Looks like it can do up to 460800 baud / 46kbytes/s with the right config settings but YMMV pushing it to it's max)MSP430F2xx user guidePage 448, 449, 450https://www.ti.com/lit/ug/slau144k/slau144k.pdf?ts=1673722314062

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 02:53:37 am
content: Your 68HC11 could do up to 250,000 baud. So 25,000 bytes /sec but you needed to clock it at 16mhz and run the bus at 4 mhz with no prescaler to get that speed. Assuming the CPU processing needed was light enough for the MCU to handle.That is an extremely old MCU from like 1984, so it's pretty limited.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 03:59:19 am
content: In the HC11, one can easily find the RTI time.Here, even if one uses the fastest 4.10 msec. In one second, you could only display 1/4.10msec = 244 samples. How about in the MSP430F2617. I couldn't even find the RTI time table in the manual. To display 3000 samples a second. The RTI time has to be 0.3 msec (1/3000 samples). Is it that fast? If not, how do you make the timer to display 3000 samples to the pc app?

author: ataradov
author_rank: Super Contributor
timestamp: January 15, 2023, 04:09:46 am
content: You would benefit from working with modern MCUs on an abstract projects before getting into that specific device.3 kHz is nothing for moderns MCUs. They are way-way more capable than a designed from 1984. Anything made in the past 20 years will work perfectly fine here without breaking a sweat.But you would have to start thinking in modern terms. You can't just ask for direct equivalents for things from the 40 year old device.Everything you want is doable, but you would have to read that long datasheet.

author: Psi
author_rank: Super Contributor
timestamp: January 15, 2023, 05:27:40 am
content: On a modem MCU you wouldn't use those timer interrupts to generate an output frequency like that.You would configure the timer to assign one of its compare channels to set & clear one of the I/O pins, all done in hardware.No timer interrupts needed.

author: hans
author_rank: Super Contributor
timestamp: January 15, 2023, 09:23:36 am
content: I agree with ataradov. Forget everything about the 68HC11; it's ancient and nothing like modern MCUs.Modern MCUs have timers with reprogrammable period registers to set up a timebase. In it's most basic configuration, a timer consists of a counter that is incremented with the peripheral clock frequency. When it equals the period register count, an interrupt is generated to the CPU, and the count is reset to 0 to automatically count up again. Using this fixed frequency timebase, you can also have the counter value compared with a programmed value to create pulses at the timebase frequency. Modern MCUs like a STM32F4 or other modern equivalents, may even have multiple compare channels on 1 timebase, so you can create complex waveforms (e.g. delay pulses, or create additional pulses on multiple I/O, etc.), trigger the ADC sampling/transfer data (presumably external 24-bit chip), etc. But, this is far too much to explain in just 1 page let alone paragraph, as these timers can have more than a dozen registers to be set up, with accompanying peripherals likewise (e.g. SPI, ADC, and/or DMA) to get everything workingautomagicallyfrom hardware. There are also vendor libraries probably, but since they expose a lot of this complexity to the user, it is also takes some time to set it up.If I were you, I would not look at doing everything from hardware at the start. 3kHz isn't that high of a sampling rate, as from experience I've only hit limitations at 250k - 500ksps from an external SPI ADC on a STM32F407 (doing everything in software). Making use of a bit overkill CPU makes writing the software much easier/forgiving as it doesn't have to be optimized as much. IMHO just generate a timer interrupt at 3kHz and then handle everything from software.The FT232 chips are very widely supported, and basically handle all of the USB protocols and drivers for you. Your host MCU only needs an UART and communicate at the proper baudrate with the FT232Rl. That baudrate is the one you open the  serial port with on your PC. From there, the processing of the data just depends on the application that can use it.In terms of baudrate, also depends on formatting. Is it a binary protocol or plaintext? E.g. 3kHz with 32-bit words is 12kB/s of data traffic, which is at the limit of 115.2kBaud. But modern chips can go much faster, say 921.6kBaud (1MBaud), so plenty of margin there as well. In that project, the ADC ended up running slightly faster, so I ported everything over to a complex timer set up + SPI+DMA transfers. It dropped the CPU load from '99%' (skipping ADC samples) back down to 5% before sending the raw data out over ethernet.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 09:31:52 am
content: In your experience with the MSP430. What is the highest frequency possible with the compare channel method? 7000 Hz? 10,000 Hz?Also for the FT232BM. Is it connection with the MSP430 pins standard? Is there any library assembly program where you can just run it and they and the PC app would connect serially?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 09:33:32 am
content: Don't waste your time in MSP430, it's a pretty old 16-bit CPU which has its users, and niche applications where it might be the best option.But generally, pick any mid-tier 32-bit ARM MCU, like something from STM32F3/F4 series to start experimenting on. ARM has standardized toolchain so you have a lot of options available.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 10:00:37 am
content: I have an existing EEG equipment based on the MSP430 with 24 bit ADC input (shown at initial page). I won't be able to solder like that.So I have to rewrite the firmware to turn it into a higher frequency EMG after I figure out how the HCTO4, HC4052M is connected to it. Has anyone tried rewriting firmware of existing hardware? Is it easy?Btw. It has extra EEPROM in the 93LC46CI due to the MSP430 having flash and you can't write individual bytes into flash (but need to erase whole segment). What modern MCU has built-in EEPROM so you don't have to add external one?Also does anyone know what pc software can make you filter the 800Hz, 1000Hz in the mV EMG waveform output? I can't program the pc software. If no public software. Where can I find programmers to write me pc software to do that?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 10:31:24 am
content: If you want to use existing hardware without de- and resoldering the MCU, make sure the MCU protection lock bits are not set, preventing the erasure of the device. But resoldering a new chip in to the same footprint is half-an-hour job for someone who has done it before. Nothing special.Otherwise than that, it's some simple reverse-engineering where the signals go and what they do. Not a difficult task for someone experienced with MCU designs.But if you have to start from nearly zero, you have a long way to go. It seems you will need some outside help.For data analysis on PC side, I'd recommend Matlab or the free alternative Octave. You'll be able to find algorithm folks experienced with Matlab because it's so widely used in education; and commercially, too.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 11:03:28 am
content: I have already read the firmware of the chip via 4 pin JTAG and MSP Flasher, even ran it at CSS and IAR and saw the assembly language and even single stepped it. But it's 27k of firmware and very complex. And I think one third of it is program to access the EEPROM as well as use auxiliary input which I don't need.I don't need the EEPROM so I'll just run basic program to run the FTDI serial output reading directly from the input.Also the MSP430 chip doesn't use its built-in 12 bit ADC. Instead the signal at the source is amplified in the VAC1 then sample at 24 bit externally using the ADS1254E (as shown in picture in original message). Is it not 24 bit external ADC is much like producing the gain without using much Op-amp? In the modern world, 24 bit ADC can replace some function of op-amps, right?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2023, 11:17:29 am
content: Quote from: planc on January 15, 2023, 11:03:28 amThere are ADCs with integrated amplifier stages available (called PGA, programmable gain amplifier; you can digitally choose between some predefined gain options). And of course, if you use an ADC which is excessively good for what you need (way more bits; but remember to look at the ENOB specification which gives more realistic idea about the true performance), and you need modest amount of gain, then you can just digitally multiply, leaving some of the ADCs input range unused. Also, if your ADC of choice has excessive bandwidth, it (partially) converts into extra resolution when you filter down the number of samples (e.g., using FIR filter); this is calledoversampling. So who knows, maybe you can go without an opamp.There are many small details like this, and for that reason, detailed specifications about how the signals look like and how they are post-processed helps choose sensible front-end. Lacking that information, one can of course always over-engineer.In any case, if I understood it right, you are going to analyze the data on PC? So the MCU part basically just reads ADC and collects the data, right? That will mean you have no trouble with the 3000Hz sampling part; in fact, it's so slowanyprogramming strategy will work: polling, interrupt-driven, or DMA.You can even use UART for data transfer: 3000Hz * 24 bits = 72 kbit/s. Add some headers, framing, etc., and the classic standard baudrate 115200 works out. In fact, around 500kbit/s is widely supported by nearly all serial-USB interfaces you ever encounter, and many work fine up to around 2Mbit/s.Matlab/Octave can import and process binary data dumped from UART just fine.

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 01:00:07 pm
content: btw.. VAC1 stands for the TLV2211. What you make of it?https://www.ti.com/lit/ds/symlink/tlv2211.pdfThe 24 bit ADC is the ADS1254E. It has serial output. Do you think it's more difficult to connect a serial output from external ADC to the MSP430 (or other MPU)?https://www.ti.com/lit/ds/symlink/ads1254.pdf?ts=1673787121100&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FADS1254Thanks for the input (no pun intended).

author: planc
author_rank: Regular Contributor
timestamp: January 15, 2023, 10:55:06 pm
content: Using an MCU internal ADC may make the programming much simpler as you don't have to connect the external ADC to the MCU. However. I read the following disadvantages of internal ADC. Do you know an MCU that addresses all the following concerns of internal ADCs (I read this at physics stack exchange (note the owner of eevblog emphasized they are not jealous of other sites, so let me mention this)):https://electronics.stackexchange.com/questions/142283/use-cases-for-an-external-adcexamples of reasons for external ADC"1. You need a different sampling technology - for instance the internal ADC is SAR, but you need to do Delta Sigma.2. The internal ADC, because it is internal, and shares the same die as the main MCU, will never be 100% free from the noise of the rest of the MCU, so an external one would be possible to make ultra low-noise3. Many external ADC parts include an amplifier stage before the converter itself, thus allowing the converter to measure a high-impedance signal directly. On many microcontrollers, the act of sampling an input signal may disturb it. Depending upon the nature of the input signal, this may vastly increase the acquisition time necessary to make accurate measurements.4. Even if an internal ADC is twelve bits wide, that generally won't mean it takes readings accurate to one part in 4096. A typical external ADC will often have better specifications than an internal one, even when both have the same advertised bit depth."In the EEG equipment based on the MSP430 I owned. They use external ADC for the above reasons. Delta Sigma, ultra low noise, 24 bit ADC.I think it would be better for me to get a whole new MCU and start from scratch. Please tell me what modern MCU has built in ADC that is Delta Sigma, ultra low noise, 24 Bit sampling? Thanks.

author: ataradov
author_rank: Super Contributor
timestamp: January 15, 2023, 11:21:44 pm
content: There is no chance you will get MCU with a 24 bit ADC that actually works well. If you need any sort of analog precision, you have to use external ADC and good analog design.Microchip SAM C21 has SDADC, but it is only 16 bits and even that start to run into noise issues because of the digital stuff.

author: planc
author_rank: Regular Contributor
timestamp: January 16, 2023, 12:48:25 am
content: If I'd keep touching my EEG pcb and trace the circuits. I'm afraid it might get Electrostatic damage by the time I figured it out. And it's expensive at $2000. Therefore I'd like to start from beginning with any MCU.Ok. What MCU is easiest to interface with the 24 bit ADC ADS1254E?https://www.ti.com/lit/ds/symlink/ads1254.pdf?ts=1673787121100&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FADS1254Please share how to interface your MCU suggestion to the above ADC. Do all MCUs have similar connections?The MCU will simply be for collection of the external ADC data and outputting it serially via USB to pc app genericly. Simple, isn't it?Also if I put everything in breadboard. What noises would be introduced by using breadbroad only?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 16, 2023, 12:57:50 am
content: Quote from: planc on January 15, 2023, 10:00:37 amQuote from: planc on January 15, 2023, 11:03:28 amYou have answered your own question there.Quote from: planc on January 15, 2023, 01:48:21 amIf you cannot extract that from the datasheet, I'm not sure creating your own firmware is within your abilities ?As already said, 3000Hz is 'slow' , the serial port speed is not an issue.The ADC is likely to be more of an issue, I see the ADS124 specs24 BITS—NO MISSING CODES19 BITS EFFECTIVE RESOLUTION UP TO 20kHz DATA RATELOW NOISE: 1.8ppmFOUR DIFFERENTIAL INPUTSINL: 15ppm (max)EXTERNAL REFERENCE (0.5V to 5V)That's quite impressive.19 bits of useful info can pack into 3 bytes which needs 9000 bytes/sec or 90k Baud.You have not mentioned channel count, but the image shows 4 opamps, so do you intend to stream 4 channels at 3kHz ?. That's then > 360kBaud of data flow.The modern USB-UARTS can manage 12M/N or 24M/N for UART speeds, the common baud rates like 115200 are simply historic suggestions. 100k and 120k and 500k will also be possible. (etc)So there will be many possible baud rates that both MSP43 and UART can manage.Check the resonator on your board and use the datasheet to calculate possible baud rates.Quote from: planc on January 15, 2023, 01:34:04 amWhat limits that ?Quote from: planc on January 15, 2023, 01:34:04 amDo you need real time display, or do you intend to capture then graph ?google finds items likehttps://github.com/xioTechnologies/Serial-Oscilloscopeand that links tohttps://www.oscilloscope-lib.com/and also there is thishttps://github.com/ccrause/LazScopeIf you use ASCII CSV, that will be slow to convert inside the MSP430, and also wastes link bandwidth, 3 bytes becomes ~ 8.25 bytes, so you need something over 1,11MbdIt maybe easier to tweak the PC side CSV ascii parser to accept a simpler/faster21 data bits packed into 3 bytes using MSB tags. That is very fast and simple inside MSP430.3 byte sets of MSB's of  can tag channel Zero frame and  can increment the channel, leaving you one spare tag of  (for things like timebase/scaling?), this simple MSB tag encode gives channel sync information too.eg A 4 channel capture frame of 21 data bits, would be streamed as 12 bytes MSB repeating as ....

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2023, 01:03:39 am
content: Any MCU can interface this device. You can use SPI, or at this speed you can easily just use regular GPIOs.I would not worry about the noise, make sure it is functional first. And then transitioning to real PCBs would be necessary for the final debugging anyway.

author: uer166
author_rank: Super Contributor
timestamp: January 16, 2023, 01:19:13 am
content: Quote from: ataradov on January 15, 2023, 11:21:44 pmEeeh, I agree in general but there are always exceptions, here's something we used successfully with 3 24 bit S-D for revenue grade metering:https://www.ti.com/lit/ds/symlink/msp430f67641a.pdf?ts=1673831875420&ref_url=https%253A%252F%252Fwww.google.com%252F.

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2023, 01:34:45 am
content: Quote from: uer166 on January 16, 2023, 01:19:13 amWith best case SINAD=89 dB, it is barely 15 effective bits. This performance does happen in MCUs. But it is far from what you can get from standalone devices.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 16, 2023, 01:49:26 am
content: Quote from: planc on January 16, 2023, 12:48:25 amAvoid breadboards !If you want to avoid reverse engineering, you may be smarter to work backwards, and search Digikey etc forEval Boardsof suitable ADCs. Those already have chips mounted and are tested.TI and ADi will have plenty, in SPI and i2cOnes like this, are even already medically focused :https://www.ti.com/tool/ADS1292ECG-FEBesides UARTS there are now available also i2c and SPI USB Bridge parts, so you could also research if no remote MCU at all is needed !You might manage this entirely from the PC side.

author: pcprogrammer
author_rank: Super Contributor
timestamp: January 16, 2023, 06:16:01 am
content: I would like to add something here in light of the original posters seemingly inexperience with it all, the thread is about a medical device, and there are special rules to take into account.When powered from mains voltage it needs proper insulation between the circuits and the electrodes attached to the test subject. This is not really needed when it is battery powered and can't be connected to a mains voltage in any way, this also means a connection to a computer via USB.Before even starting with a design of any electronics I would make sure to know about all the regulations surrounding this type of device.

author: planc
author_rank: Regular Contributor
timestamp: January 16, 2023, 08:04:29 am
content: The EEG device has 4000V H11L1 opto isolator (white chip) to the electrodes. The USB socket is the silver at the bottom.It's all difficult to trace so I think I'll just get the ADS1292ECG-FE suggested by PCB.Wiz.But just curious. As a PCB.Wiz. Can you trace all the circuits above?Also you asked why the EEG pc app limit it to 256 samples per second.This is because the brain waves are only up to 50 Hz. So the 256 Hz sampling is almost 5 times (satisfying the Nyquist sampling theorem).Also brain waves are in microvolts.. While the high frequency EMG I need is in millivolts. So the EEG equipment has more amplification than I need.I think your suggested ADS1292ECG-FE will be great.https://www.ti.com/tool/ADS1292ECG-FEI downloaded their free app. It seems to do 2000 Hz?? I did even try inputiing up to 100,000 Hz. Or did I misread something?

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2023, 08:11:54 am
content: The low pass filter cut off frequency has nothing to do with sampling rate.You will have to take this one step at a time. First of all get any MCU board and blink and LED and send some characters over UART. Get familiar with peripherals. Then connect the ADC board and start sending real samples.There is too much going on to get is all working at once from scratch.

author: planc
author_rank: Regular Contributor
timestamp: January 16, 2023, 08:30:43 am
content: I have written so much programs with the 68HC11 hence familiar with MCU.What is meant by low pass filter then? Sampling of wave is taking samples of it. I want it to sample at 3000 Hz so I could get signal at 1000 Hz.

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2023, 08:39:23 am
content: There is no need to attach pictures explaining trivial things.That tool does further filtering of the samples. As you can see it has adjustable low-pass and high-pass filter plus a notch filter to reject mains (50/60 Hz). None of this tells anything about the sample rate. Generally to implement 2 kHz low pass filter, the sampling frequency must be at least 4 kHz. But as you said, this field lets you enter any value, so who knows what the actual sample rate is. But I bet it is documented somewhere in their documentation or can be configured in settings.You say that you have experience with 68HC11, but this is a 40 year old device. And this whole task is trivial for anyone familiar with MCU programming.

author: planc
author_rank: Regular Contributor
timestamp: January 16, 2023, 09:11:00 am
content: https://www.ti.com/lit/ug/slau384a/slau384a.pdf?ts=1673847243143&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FADS1192ECG-FE%253FHQS%253Ddis-dk-null-digikeymode-dsf-pf-null-wwe%2526DCM%253Dyes%2526distId%253D10You are right. The app PC actual sample rate seems to be only 500 samples per second. I need at least 3000 samples per second.So PCB.Wiz, the eval board you suggested won't meet the requirements.Hmm.. Ok. Where can I find service (where I'll pay) to design and build the circuit and make the firmware and PC app for 10mV 3000 samples per second signal to be outputted to PC and display filtered waveforms at 600 Hz, 700 Hz, 800 Hz and every hundred up to 1500 Hz.What company can do that? or anyone of you can do that (for a fee)?

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2023, 05:55:42 pm
content: The idea of a kit is that you get the proven hardware right away, you can then use it to make your own software that does whatever you want.I'm not aware of any contract services like this, but they all would require a very detailed specification. Something we have not seen here yet. So, your starting point would be come up with this and it might help us understand what you want exactly.In low noise systems every part matters, it is not just a matter of the ADC board design. It is not an insignificant project, it would be very expensive.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 16, 2023, 06:21:29 pm
content: Instead of a consult firm who is tasked to develop "just the code" or "just electronics + code" based on a specification, it might be a better idea to find someone who takes a more holistic approach to the problem, i.e. you will spend several hours just discussing about the problem, brain waves and whatnot in general. As a result, they will gain understanding what you arereallytrying to achieve and can suggest ways to simplify the problem - andthendesign electronics / write firmware which does what you need. Without this wide and deep discussion into the physics side you and any subcontractors are possibly going to solve the "wrong problems". Similarly, resources might be better spent if the analog/firmware/algorithm designer learns about this EMG thing directly from primary sources, instead of / in addition to yourself acting as a middle man trying to come up with analog specifications.This is how I usually work, for example, but of course finding someone close to you who also has time for this problem could prove quite difficult.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 16, 2023, 07:57:33 pm
content: Quote from: planc on January 16, 2023, 09:11:00 amThat's likely merely a default, so I would look for the source code for the TI Eval board.Google finds this "Kit source code / ADS1292ECG-FE Labview PC software source code."and TI link says thisSUPPORT SOFTWARE ADS1X92XEVM-SW — Software for ADS1x92xECG-FE = Requires export approval (1 minute)Quote from: planc on January 16, 2023, 08:04:29 amIt just takes time.Make yourself a low voltage milliohm sensor (low voltage current source and a opamp and LED ) - that gives quick trace checks with no damage risk.Next, print out the datasheets and then use your eyes and meter to find the PCB connections, starting with the most likely pins. Slowly, you create a schematic.Quote from: planc on January 16, 2023, 09:11:00 amThat's a strange wording.Do you want a FFT histogram with 100Hz spacing, or do you want what you have written, which is 9 time domain traces, each with a slightly different filter (100Hz filter increments)Notice the TI demo is a time domain display.

author: eutectique
author_rank: Frequent Contributor
timestamp: January 17, 2023, 02:45:23 am
content: You've omitted the most interesting part of page 318:SUMMARY OF AURIC COLOR FREQUENCIESColor Approximate Central FrequencyLow blue (muscle) 2 or 200 HzGreen 3 or 300 HzYellow 4 or 400 HzRed 5 or 500 HzOrange 6 or 600 HzHigh blue 7 or 700 HzViolet 8 or 800 HzCream 10 or 1,000 HzWhite 11 or 1,100 Hz upI scrolled through all 368 pages and didn't see a single formula. In the book titled "Science of the Human Vibrationsof Consciousness".Why do I have a feeling that someone is training chatgpt4?

author: ataradov
author_rank: Super Contributor
timestamp: January 17, 2023, 02:51:02 am
content: Yeah, I suspected that some quackery is going on.

author: eutectique
author_rank: Frequent Contributor
timestamp: January 17, 2023, 02:57:09 am
content: Sorry, could not resist. Page 315.The small equipment shown beside the person is a miniaturized, modular sensing instrument, which is like a battery-powered telemetry EMG. Actually, it is a small FM broadcasting system with an amplifier and transmitter for each channel. Note the 12 modular plug-in, white boxes comprise six IRIG channels — with an amplifier and transmitter for each channel. The IRIG channels that we used were numbered 11, 12, 13, and 14 to indicate the recording capacity of each channel. The highest channel that we used was IRIG 14, with a sensing capacity up to 20 thousand Hz.We had discovered that the regular, hard-wire instruments (operated by electricity) used for EMG, ECG and EEG did not pick up the entire millivoltage signal of the energy field. Hard-wire equipment we designed later allowed us to capture up to 200 thousand cycles per second from the energy field. When the two instruments, telemetry and hard-wire simultaneously recorded the energy field, the telemetry information was a perfect harmonic of the hard-wire instrument, yet of lower frequencies.In Exhibit 1, the bipolar (2) surface sensors of silver, silver chloride are affixed to the solar plexus or "emotional body" areas. The ground, or neutral reference electrode, is on the wrist.Continuous energy field signals were beamed via the FM transmitter to receiving instrument panels. These data were observed from oscilloscopes, and a print-out, and by further amplifying the sound. At the same time, the energy field data were recorded on a magnetic tape.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 17, 2023, 07:25:06 pm
content: Quote from: planc on January 17, 2023, 12:06:06 amSo you actually did that, and got the software and circuits ?Quote from: planc on January 17, 2023, 12:06:06 amDid you drill into the schematics of any of the adc eval boards ?Connection of a SPI ADC is relatively simple - you find the MCUs SPI capable pins, and connect them to the ADC SPI pins. That's a few minutes work.Then, you need code that activates the SPI peripheral on the MCU to meet the timing requirements of the ADC, testing as you go.That's what EVAL boards help you with,as they have already working examples.Quote from: planc on January 17, 2023, 12:06:06 amThat's labeled as a frequency-time plot, and I have seen those called a waterfall plot. (see post below)These days the axes are usually swapped, but there is existing work you can tap into for waterfall plots.Examples are herehttps://en.wikipedia.org/wiki/Waterfall_plotQuote from: planc on January 17, 2023, 12:06:06 amPossible Microsoft's QuickBASIC (or similar) "Microsoft released the first version of QuickBASIC on August 18, 1985 on a single 5.25-inch 360 KB floppy disk."It is doing time domain voltage-time plots, and inset boxes called cross plots are XY graphs of two of the channels. Most oscilloscopes can do that plot.Quote from: planc on January 17, 2023, 12:06:06 amThen you are out of your depth, in even specifying what you need someone else to do.Maybe you should shift focus to Oscilloscopes, which can capture and record waveforms, and better ones have processing software for waterfall plots. (google hints Rigol scopes can do waterfall)If you ultimately plot pixels on a screen, you do not need 24b ADC, just a higher end scope is fine.eg try thishttps://www.zeitnitz.eu/scope_enand thisDHO1000 HIGH RESOLUTION DIGITAL OSCILLOSCOPEShttps://www.rigolna.com› products › dho1000Set your frame number to capture and visualize using a density, waterfall, perspective, or mosaic display. Utilize UltraAcquire to capture small, ...

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 17, 2023, 08:53:00 pm
content: Quote from: planc on January 17, 2023, 12:06:06 amThat's labeled as a frequency-time plot, but it's a little different when I look closely. There are too many related lines, which suggests multiple capture channels rather than a single spectrum spread.Is there more info on the actual experiment setup ?What they may have done for this, is construct ~ 10 sharp audio band filters, and then plotted the envelope amplitude output from each of those filters.However, the plot also varies in density :FWIR 'way back' there were spark/arc plotters way back, that left a mark and more time in that area, meant a thinker / darker line, or the higher the drive current, the larger the spots.If we presume they used that tech, and the line thickness is then amplitude, to get some small frequency deviation info, (within each audio band) you could place a monostable after an audio bandpass (that's how tachometers work)It's rough, but useful, and the plots will be multi 'line' XYZ* in nature, and may cross-over into each others territory, depending on the band-pass and mechanical plotter offsets - which is what your image does.*Z is the line thickness.Quote from: planc on January 17, 2023, 12:06:06 amYou are over thinking this, and in 2023 terms.Certainly 20,000Hz is just audio band, and Audio amplifiers have been around as long as loudspeakers, which is over 100 years !LCR band filters are certainly easy 1970's technology, and impulse tachometers date from at least the 60's, and ferrite cores date from the 30'sDoing this in the 70's is not going to fit in your pocket, but it's bench-sized and repetitive (~10 channels) audio level tech, so certainly within any decent lab ability.

author: gf
author_rank: Super Contributor
timestamp: January 17, 2023, 09:23:47 pm
content: Audio CD was invented in the 1970's too.So yes, it was indeed possible.Btw, since it is just audio frequency, what about using a PC with a good soundcard to capture the signal? Possibly with an additional pre-amp. 1...10mV is basically microphone level.

author: planc
author_rank: Regular Contributor
timestamp: January 17, 2023, 11:06:12 pm
content: Quote from: PCB.Wiz on January 17, 2023, 07:25:06 pmIf you will read the following Texas Instruments export approval before downloading the software. It doesn't prohibit you from downloading it (you are not in any of the sanctioned country). In the second screenshot is the BIS description of control product for export. I spent 30 mins researching about it as I nearly ordered the hardware. And it is not prohibited to get it out too. But the reason I didn't order the product was because of Ataradov warning in time that the actual sample rate may not be the one listed in the low pass window (which you can even type as 100,000 Hz).Please try to download the software now and see if you could adjust the 500 samples per second seeming limit to 3000 samples per second. For now. I only need one channel, not 6 or 12. One channel is enough just to probe the 3000 Hz sector space at 1 to 10mV just to see if there is something there. If not, then ok. I'd be as happy and forget about this all.https://www.ti.com/tool/ADS1292ECG-FEMCU products are controlled under 3E002.c if it matches the description:"c. Designed to perform more than eight 16-bit 'fixed-point' multiply-accumulate results per cycle (e.g. digital manipulation of analog information that has been previously converted into digital form, also known as digital "signal processing".The hardware doesn't match that description, soyou can adjust the software for 3000 Hz, then anyone outside can order it too without the United States arresting you or putting you in Federal Prison or initiate Extradition proceeding for acquiring an MCU.

author: planc
author_rank: Regular Contributor
timestamp: January 18, 2023, 11:43:45 pm
content: Quote from: PCB.Wiz on January 17, 2023, 07:25:06 pmThis is the last time I'll post images of these. You won't find these anywhere because the ordinary public can't buy them but only those with certain license.You said the SPI ADC connection to the MCU is very simple. You only connect them directly. In the above ADS1254E ADC (at right side) and the MCU at left. There are many ICs detours in between them. INA 122U, HC4052M, HCTO4, MV358I. Which of them do you think is usually added? (note the white thing are just H11L1 4500 volts opto-isolator).The following is zoom of the MSP430, and the pinout designations. Notice that the MSP430 pin P3.6/uca1TXD/UCA1SIMO (top 2nd pin from right) is connected to pin5 (A3 input) to the hex inverter HCTO4. Have you seen the ADS1254E need to pass through the HCTO4 before getting to the MSP430? Why do you have to hex invert the external ADC to the MCU?Lastly. SPI connections are like this:Where are the SPI corresponding pins in the ADS1254E?I have googled for hours yesteday but couldn't find the answer. Many thanks for your help PCB.Wiz!

author: ataradov
author_rank: Super Contributor
timestamp: January 19, 2023, 12:07:21 am
content: ADS1254E is not really an SPI device. You can just use SPI to get the data, but you need to do extra work as well.it uses SCLK for the clock and DOUT as the data. But DOUT is also used as a ready signal. So, you need to connect SCLK to the SPI clock and DOUT to the MISO. But then you need to keep MISO pin configured as a GPIO and read its value. When the value goes low, it indicates that the data is ready. You then need to switch to SPI mode and clock in 3 bytes. Then switch back to GPIO and repeat.

author: errorprone
author_rank: Contributor
timestamp: January 19, 2023, 01:48:49 am
content: HCT04 could be used to level shift between a 3V MCU and 5V ADC since it has TTL inputs instead of CMOS ones.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 19, 2023, 02:27:59 am
content: Quote from: planc on January 18, 2023, 11:43:45 pmThe H11L1 are schmitt optocouplers, so they look to have isolation between the analog and digital portions here.The designer may have put some buffers between the opto's and MCU, use your low voltage continuity checker to trace the CLK and DATA signals.

author: planc
author_rank: Regular Contributor
timestamp: January 19, 2023, 03:17:59 am
content: I use the above Electrostatic Discharge protection devices whenever I touch the EEG electrodes.. They are, ESD mat, ESD wrist bands, both connected to ground, and even make sure the humidity is high (to naturally conduct static to ground via droplets of humidity) in air. But I can't take chances touching the chips to trace longer period because of risk of ESD damage. The ADS1254E warns thatTherefore I would not try anymore to trace the external 24 bit ADC complex pathways to the MCU to avoid any subtle performance degradation from slight ESD damage ruining the $2000 equipment which I won't be able to buy again (I had to acquire it from licensed medical doctor for experimental purposes). Look at the back of the PCB how complex the connections are.By the way. Do you know what the labels or wordings at the right near top mean? Also Is there a pc software where you can overlap the front and back images of the PCB together and you can rotate it in 3D and trace them? You can do it as a PCB.Wiz, right? I won't attempt to trace the hardware in detail anymore to avoid risk of subtle ESD damage.Fortunately. The EEG module has additional auxiliary inputs that makes use of the MSP430 built-in 12 bit ADC chip itself. So I'm looking for a generic software libarary that can read from all ADC channels and output to the FDTI USB chip.I downloaded the latest FDTI chip drivers and it worked with the module, that means the output connection is generic.Therefore there must be library to output the EEG unit MSP430 built-in 12 ADC input. Can you guys share the generic firmware program to do that?It took me weeks to figure out how to do that with the HC11 programming learning its assembling language instructions. Now I can't spend months just to figure out the basic library routine already available in the public. So kindly share the program. Thanks.

author: planc
author_rank: Regular Contributor
timestamp: January 19, 2023, 08:19:01 am
content: Quote from: PCB.Wiz on January 16, 2023, 01:49:26 amUnfortunately. The direct auxiliary input of my EEG module that uses the MSP430 chip built is 12 bit ADC has full scale range of 0-2.5 volts and accuracy of 0.2 millivolts. That means if the input would be 1mv. It can only digitize it 5 levels only? This is versus the external ADC ADS1254E 24 bit with listed EEG A/D accuracy of 0.024 microvolts (NOT millivolt) and 200 millivolts A/D Full Scale Accuracy.So your device suggestion is still the best. But the sampling limit is only 500 samples per second. Can you make it into thousands? If you have time, please download it. No problem with export as you are not uploading it to NK.I read the following about a TI evaluation board based on EEG.https://www.ti.com/tool/ADS1299EEGFE-PDKand a question and answer related to it:https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/693245/ads1299-does-the-ads1299-capture-eeg-signals-require-an-external-amplification-circuitUnfortunately, I don't have email company account which is required to register and ask questions there.My question is. What would happen (in an ADC context) to an EEG device that expects microvolts input if the input is in the millivolt ECG/EMG range instead? A typical EEG has 0.024 microvolts A/D accuracy and 200 millivolts A/D full scale range.I can't interpret my EEG screen output because there is no amplitude measurements.

author: gf
author_rank: Super Contributor
timestamp: January 19, 2023, 10:41:53 pm
content: Quote from: planc on January 19, 2023, 01:19:27 pmYour aim is to capture signals in the audio frequency range, and all I wanted to say is that soundcards (or audio interfaces, or however you want to call them) are basically capable to do that. The idea seems not to be new -- I also foundthis article.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: January 19, 2023, 10:46:26 pm
content: Quote from: planc on January 19, 2023, 11:02:59 amSearch AliExpress et al for USB sound cards.The very simplest/very cheap ones have single MIC jacks, and then you can get 2 MIC / headphones, and then 2 MIC + Line in + SPDIF links all for quite low prices.Quote from: planc on January 19, 2023, 01:19:27 pmNot for what they can do.Quote from: planc on January 19, 2023, 01:19:27 pmAM radios manage 455kHz IF and 1MHz RF sections for many decades before that.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 19, 2023, 10:53:21 pm
content: Quote from: gf on January 19, 2023, 10:41:53 pmWell, conversion-wise, sure, a sound card can do the job.A few points:- You'll still need proper conditioning (amplification) of the signals, EEG signals are very low voltage, and you very easily get coupled noise,- EEG requires multiple channels to be useful - something you won't find in a sound card, unless you go for like a studio audio interface with 16 or 32 channels, I wouldn't see the point of using that then rather than more ad-hoc gear,- Important: the interface from electrodes should absolutely be ISOLATED. Anything that would be connected to a computer directly without galvanic isolation is not fit for being connected to the scalp through electrodes.

author: gf
author_rank: Super Contributor
timestamp: January 19, 2023, 11:37:44 pm
content: Quote from: SiliconWizard on January 19, 2023, 10:53:21 pmThe pre-amp is supposed to do that.QuoteThe authors of the the PubMed paper obviously did not care. But they did not scalp through.The question is, what's good enough?Can we consider a laptop running on battery w/o external connection to mains or anything else as sufficienctly isolated?Would an USB isolator between PC and an USB sound card provide sufficient isolation?The opamp inputs are coupled via capacitors. Do they provide good enough galvanic isolation if Y types are used?

author: Nominal Animal
author_rank: Super Contributor
timestamp: January 20, 2023, 12:45:23 am
content: Quote from: planc on January 19, 2023, 11:50:18 pmMy current favourite,Teensy 4.0, can do1,000,000 samples/seccontinuously writing them to an SD card (in binary form); 2,500,000 samples/sec when interleaving the two ADCs. Although the ADCs have nominally 12 bit precision, only 10 bits or so are noise-free on this board.Teensy 4 also have a (actually two) native USB 2.0 High Speed (480 Mbit/s) interface, that I've verified can do well over 200,000,000 bits/sec (25 Mbytes/sec) in one direction.Then again, it is an NXP i.MX RT1062 running at 600 MHz. Costs only $24, though, and comes with Teensyduino, an Arduino add-on for programming it in the Arduino environment.Obviously, the exact capabilities vary from MCU to MCU. Some have only one ADC, some have several (in which case they can often be interleaved, so that one takes a sample while the other is still in the process of conversion), possibly multiplying the maximum sample rate (even from a single source signal).Teensy LC(NXP MKL26Z64VFT4, ~ $13 but no stock right now, USB Full Speed 12 Mbit/s) runs at 48 MHz, and has a single 16-bit ADC (about 12-13 effective bits), but I haven't checked the maximum sample rate on it (but seepedvide's ADC library). I'dexpectit to be somewhere between 100,000 and 400,000 samples per second (using HIGH_SPEED and ADACK_6_2), though, if that helps.In general, I do like microcontrollers with native USB interfaces, because of the increased bandwidth – even USB 1.1 Full Speed (12 Mbit/s) on 8-bit AVRs like ATmega32U4 can do over a million bytes per second over USB Serial – and implementation options: if you want a custom keyboard/mouse/joystick, you don't even need any OS drivers at all, just program the microcontroller USB endpoints, connect the buttons/sensors/etc., and It Just Works.(I have looked at various data acquisition ADCs that have very nice properties, so you definitely do nothave touse theinternalADC on the MCU. A SPI bus running at a few MHz, over digital isolators like Si866x, and a small isolated DC-DC controller followed by some serious smoothing and a linear regulator, and you can have a fully isolated analog sensor frontend. I'd love to have one of those, myself, just for fun.)As I've mentioned before in other threads here, the aforementioned Teensies are excellent for hobbyist and development tests, but not that suitable for basing your commercial products on. Definitely good for one-off projects; they're well designed, and theforumis friendly and knowledgeable, and the developer (Paul Stoffregen of PJRC) participates there a lot. Only the bootloader (which you can buy separately in a pre-programmed chip) and the exact board files are proprietary.For hobbyist and one-off purposes, I know for a fact that it is a good fit for interfacing to various kinds of sensors (Teensy 4.1 if collecting data to an SD card) and displays and such, because that's what I typically use them for. But I am only a hobbyist, not an EE, and do not develop any products; just gadgets I or my friends or colleagues need for a project or another. Stuff like Pt100 temperature sensors, high-frequency current monitoring for SBC current draw (to see short spikes, since they often do not have much (enough) capacitance on their main voltage buses), OLED and IPS TFT display modules, buttons and joysticks, and such.

author: planc
author_rank: Regular Contributor
timestamp: January 20, 2023, 06:08:22 am
content: Quote from: gf on January 19, 2023, 10:41:53 pmThe problem with sound card is the low input impedance. I read in that article:For high frequency say 5000 Hz, what is the impedance of the skin?When I googled for the best 24 bit sound cards, for examplehttps://www.amazon.com/192kHz-Digital-Mixing-Recording-Production/dp/B0B4YG4CBCI saw the input impedance spec as only 18.5 kOhmMy EEG has the following input impedance:More than 1000 GigaOhm input impedance! What sound card brand/model has this value too guys? Is it expensive to use 1000 GigaOhm input impedance amplifier in sound card?

author: ataradov
author_rank: Super Contributor
timestamp: January 20, 2023, 06:23:17 am
content: Don't attach electrodes to the sound card directly, use amplifier with whatever input impedance you need.You are swinging from one extreme of designing a whole bunch of custom equipment to the other extreme of not using any equipment at all.

author: gf
author_rank: Super Contributor
timestamp: January 20, 2023, 01:40:00 pm
content: Quote from: planc on January 20, 2023, 06:08:22 amWell, if you continue reading, then you will read how the authors have addressed this issue by breadboarding a simple pre-amplifier, consisting of only a few components.

author: eutectique
author_rank: Frequent Contributor
timestamp: January 26, 2023, 10:21:49 am
content: Quote from: plancHere we go.These are all miracles of technology. Just google"the more expansive fields were skewed upward"and you get exactly one match.(There will be two after my comment, I can prevision the future)

author: pcprogrammer
author_rank: Super Contributor
timestamp: January 26, 2023, 11:01:40 am
content: Quote from: eutectique on January 26, 2023, 10:21:49 amYour crystal ball is to quick

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 26, 2023, 06:46:51 pm
content: What?

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2023, 06:58:33 pm
content: Yeah, this escalated quickly.