What does this circuit diagram say about triggering a reset? - Page 1
Forum section: electronics / beginners

author: sertyrion
author_rank: Newbie
timestamp: December 16, 2019, 10:23:11 pm
content: I am working with a ADUCM350 chip on the Spectra and trying to upload firmware to it.I am able to connect to the device with a Segger JLINK with VCOM support. I'm able to read memory of the chip, however it fails at erasing the chip.In looking up documentation about the Analog Devices ADUCM350, it says this about erasing the chip:QuoteThere doesn't seem to be any button the Spectra to do that, looked through documentation on PCB git.However there is a diagram that talks about "RESET" and "DOWNLOAD" on page 4 of the pdf:https://github.com/OpenEIT/EIT_EE/blob/master/Spectra.PDFAttached is the relevant image. What is that circuit diagram saying about triggering a reset? I can provide images of device if needed.https://www.crowdsupply.com/mindseye-biomedical/spectra

author: Ammar
author_rank: Regular Contributor
timestamp: December 16, 2019, 10:34:40 pm
content: Without reading any of the links or resources you provided (which you should provide just in case, so thank you) you can tell from the circuit diagram that the reset is active low. The pull up resistor holds the reset pin high and connecting it to GND will reset the device. The capacitor is there to provide filtering/smoothing to stop any spurious signals getting into the reset pin and causing a false reset.

author: rstofer
author_rank: Super Contributor
timestamp: December 17, 2019, 02:39:25 am
content: At startup, the capacitor will be discharged. When power is first applied, the capacitor holds the reset signal low for a short period of time while it charges. This is a very common approach to power-on reset.We know that the time constant Tau=R*C is 1 ms and in that time the voltage on the capacitor will charge to 63% of Vcc. Without doing the math, it is likely that the signal will be below the logic '1' threshold for, perhaps, 500 us. Maybe a little less, maybe a little more, it depends on the threshold voltage.R is in Ohms, C is in Farads so Tau = (1 * 104) * (1 * 10-7) = 1 * 10-3= 1 msWe also know the charging equationVout = Vin * (1-e-t/Tau) and it turns out that at t = 1 Tau the output is 63% of the input.

author: sertyrion
author_rank: Newbie
timestamp: December 17, 2019, 03:12:31 pm
content: Thanks for the responses.I've tried grounding the reset pin on the SWD programming header, then pulse a reset, and that doesn't seem to make a difference.Here is the pdf on how to initiate a serial download:https://www.analog.com/media/en/technical-documentation/application-notes/AN-1262.pdfI'll keep poking at it.

author: rstofer
author_rank: Super Contributor
timestamp: December 17, 2019, 04:08:23 pm
content: Are you sure you are supposed to use JTAG? The AN-XXXX document talks about 'serial' programming and the board apparently has the FTDI USB->Serial chip. Does the serial port show up in Device Manager?

author: sertyrion
author_rank: Newbie
timestamp: December 17, 2019, 04:52:40 pm
content: I have a Segger Jlink hooked up to the SWD programming header.The serial port does show up in the "CM3WSD" tool, so it sees the device.The attached is a screenshot from the serial download monitor. For me, after "Press Download and pulse Reset on hardware", I reset the device. However the next message in program is "Message received, waiting for correct ID string".So I think it isn't sending back the correct sequence indicating a download mode.

author: sertyrion
author_rank: Newbie
timestamp: December 17, 2019, 05:45:28 pm
content: Just some more info.I plugged in both the Jlink and Spectra device into windows comp.Both show up in device manager.Using the device, it just does default behavior (spitting bio impedance numbers over serial)Using the Jlink, it waits on "received. Waiting for correct ID string"Over Jlink interface, this is the error I get with chip erase.However I can read the memory of the device just fine over Jlink.

author: rstofer
author_rank: Super Contributor
timestamp: December 17, 2019, 06:16:05 pm
content: In your Reply 5, the dialog is asking you to press and hold Download and press and release Reset then release Download. This is a common sequence for serial programming. On many boards, the serial port control signals (CTS, RTS) are used to perform this function. Do you have those buttons? I'm not going to wade through the schematics but follow the CTS and RTS signals and see if they are used on the Boot and Reset inputs. Coordinate with the chip datasheet.What are the two check boxes for? It reads like they are used to enable the serial programmer to control the Reset and Download buttons. This is also fairly common.

author: sertyrion
author_rank: Newbie
timestamp: December 17, 2019, 06:23:38 pm
content: Thanks for the reply.There are no buttons on this production board.There is this section of the data sheet that contains info on CTS and RTS but I don't see where that is on the actual device. I'll keep looking for that though.For the two checkboxes:If Autorun is selected, CM3WSD issues a reset commandafter flashing.If Autoflash is selected, CM3WSD repeats the currentselected action until cancelled. This is useful if the sameaction (for example, mass erase) needs to be run on anumber of parts.