Min BW for Oscilloscope for PIC32 experiments not production .1 to 4 MHz ? - Page 1
Forum section: electronics / beginners

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 01:06:13 am
content: HiWhat do you think would be the minimum bandwidth of an oscilloscope to experiment with ahttp://www.microchip.com/wwwproducts/Devices.aspx?product=PIC32MX250F128B&utm_source=&utm_medium=MicroSolutions&utm_term=&utm_content=MCU32&utm_campaign=PIC32MX250F128BI am not looking for a scope (I have a DS1054Z). I am just wondering if a cheap USB or DSO could be used as a learning tool with this chip. Not a production tool. Maybe to just look at and trouble shoot I/O signals.I have seen cheap scopes from 100 KHz to 4MHz and I am wondering if this range could be used.Again I am looking opinions on a MINIMUM bandwidth, not a BW that can check everything just a BW that could do something.TIA

author: singapol
author_rank: Frequent Contributor
timestamp: August 17, 2015, 05:31:49 am
content: The guideline is 5 times the bandwith of the signal you want to investigate or esle everythinglooks like a sine wave.Example: for a 10Mhz. you need 50Mhz.Since you have 1054z what's the problem?

author: rs20
author_rank: Super Contributor
timestamp: August 17, 2015, 05:55:42 am
content: I agree with everything singapol says; also consider logic analyzers if you're only dealing with digital signals.

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 06:32:40 am
content: QuoteI am wondering how cheap a PIC32 lab could be put together. The Microstick II seams to be about $40 and the software free and a USB charger is cheap, I am wondering how much to put together something useful. The Cornell lab uses a Tektronix TDS1002 oscilloscope and a B&K 4040a signal generator for their lab. What if I want to put together 20 labs - buying 20 Rigols or 20 Tek and 20 B&K is way way way out of my price range. Maybe I should ask "what is the cheapest PIC32 lab you can design?" After this post dies I will ask this question.In regards to the logic analyzer, I will start looking into this.thanks

author: singapol
author_rank: Frequent Contributor
timestamp: August 17, 2015, 10:31:09 am
content: Quote from: ez24 on August 17, 2015, 06:32:40 amSurely you are joking...just hookup your Rigol whenever you need it, no need to permanently tether it to a mcu?As for a pic32 lab, can try this microchip pic32 starter kit:http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=DM320001&utm_source=&utm_medium=MicroSolutions&utm_term=&utm_content=&utm_campaign=PIC32+Starter+Kit+Add whatever you need as you go along...

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 07:16:36 pm
content: QuoteOne thing the professor said in his 2012 YT classhttp://people.ece.cornell.edu/land/courses/ece4760/Was that there were about 80 students and 40 labs and 40 MCUs are destroyed each semester in his labs. So that works out to an average of every lab blowing out a MCU and he said the most common way was damaging the I/O pins (I forgot short or power on them?)Well anyway that is why I bought a Microstick II, the MCU can be replaced and it can be plugged into a breadboard. Another thing that is drying me nuts are all the different "development" options from Microchip and others. If I cannot get anywhere with the Microstick II, I will keep the Starter Kit in mind. It looks like it comes with 35 samples. And as a hunch, I guess it is easier to deal with than the Microstick II.Thanks

author: JoeN
author_rank: Frequent Contributor
timestamp: August 17, 2015, 08:18:08 pm
content: Quote from: ez24 on August 17, 2015, 07:16:36 pmI don't know exactly what the output driver on a PIC32 looks like, it's probably documented somewhere, but setting a pin to output and driving it low while connected to the high rail through low impedance or the other way around is the normal way of frying an output driver or the whole chip. Normally it's impossible to fry pins set to input as they will be very high impedance inputs. Probably the most likely way of frying a whole chip is to reverse one or more of the power supply rails.

author: bktemp
author_rank: Super Contributor
timestamp: August 17, 2015, 08:29:02 pm
content: Quote from: JoeN on August 17, 2015, 08:18:08 pmI have never destroyed an output pin by shorting it to Vcc or gnd. It can happen, but it is unlikely because of the weak output drivers.I have killed quite a lot of controllers by connecting a pin to a higher voltage. 5V tolerant pins set to input can easily be damaged because there is no protection diode going from each pin to Vcc. So even a very low current can fry the gates of the input buffer when the voltage goes above 7V.

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 09:10:28 pm
content: Quotethanks

author: Howardlong
author_rank: Super Contributor
timestamp: August 17, 2015, 09:45:42 pm
content: I have numerous PIC32 starter kits and Microsticks that I use for quick prototype testing.Imho, the Microstick II is a better way to start because it breaks out into a 28 pin DIP on the underside that you plug directly into breadboard. The PIC32 Starter Kits on the other hand have a high density connector that demand other board(s) to break out.Not only that, but the PiC32 on the Microstick II is much more of an entry level device so there's less nonsense to get in the way of getting started. Plus, if you do bust it, you just buy another $3 PIC for the Microstick, it's socketed.Regarding busting the IO pins, it can be for many reasons, I'd hazard sticking 5V on a 3.3V pin being one of the most common reasons. There are those who have done it and those who will. Here's a PIC24 I sacrificed accidentally a few weeks ago that way.

author: ez24
author_rank: Super Contributor
timestamp: August 17, 2015, 09:56:58 pm
content: Quotewhew ! thanks

author: AG6QR
author_rank: Frequent Contributor
timestamp: August 18, 2015, 03:08:25 am
content: For student experiments, one way is to determine what BW scope you can afford, then use a clock speed slow enough to make the PIC's pins transition slow enough to be seen on your scope.IOW, slow the PIC down to match the scope, instead of busting your budget getting scopes fast enough to match the fastest your PIC is capable of.

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 03:51:55 am
content: Quote from: AG6QR on August 18, 2015, 03:08:25 amI wondered about this - thanks

author: Howardlong
author_rank: Super Contributor
timestamp: August 18, 2015, 06:26:51 am
content: Digilent's Analog Discovery is a combined PC based scope/AWG/logic analyser. I wouldn't usually recommend a PC based instrument, but I will make a notable exception in this case. I regularly use when I'm travelling, on the train or plane (but be careful on a plane, you might get some interesting attention!)Depending on your educational status, there are discounts. Alternatively, Microchip Direct seems to offer it significantly cheaper than anywhere else for a commercial sale.While the scope bandwidth only states 5MHz, in practice it's a lot more, especially if you use the add on BNC adapter with proper probes. I measured it at 33MHz, but keep in mind the sample rate is only 100Msa/s.The reason it's highly rated on here is not just the price and hardware features it offers, it also has really good software, something sadly lacking in my experience in many PC based instruments.

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 07:12:10 am
content: Quote from: Howardlong on August 18, 2015, 06:26:51 amthanks I will look into this, I forgot about it. I also sent your message tohttps://www.eevblog.com/forum/testgear/digital-oscilloscope-comparison-chart/In case fanOfeeDIY wants to include USB scopes into his spreadsheet someday