Noise on the reset line of Atmel ICE ISP - Page 1
Forum section: electronics / general

author: Kalcifer
author_rank: Regular Contributor
timestamp: June 01, 2021, 11:23:46 pm
content: (https://imgur.com/a/KXJqzba) is a video of what I am seeing when I probe the reset line of my Atmel ICE programmer. The noise, as seen in the video appears when Vcc and GND of the ISP are powered, and is independent of the Atmel ICE being connected via USB.What would be causing this? It was working just fine the other day.

author: ataradov
author_rank: Super Contributor
timestamp: June 02, 2021, 12:59:16 am
content: So is Atmel-ICE itself powered or not? If not, I can see that happening. It uses level shifters that are powered by the target VCC, but the inputs are provided by the internal circuitry that is powered from the USB. Having ICE connected to the target board while not powered is not a valid use case.If ICE is powered, then something is broken.

author: Kalcifer
author_rank: Regular Contributor
timestamp: June 02, 2021, 01:07:07 am
content: Quote from: ataradov on June 02, 2021, 12:59:16 amIf you mean through USB, I have tested with both the USB connected *and* disconnected. Both show the same behaviour.Also I would like to note that I have notice that, as shown in (https://imgur.com/a/Iu5r5o7) video, there is a delay between the Atmel ICE recieving the Vcc power and the noise. It is not instantaneous. I should also note that the amount delay that there is, is proportional to how long the atmel ICE has been sitting without power for, almost like a capacitor discharging, and recharging.What is also strange, is that the atmel ice seems to be drawing a substantial amount of current for some reason. around 5-6mA, when it (from my experience) shouldn't really be drawing much of any current. This tells me that perhaps the Atmel ICE is fried...? How on earth would that have happened, its just been sitting.

author: ataradov
author_rank: Super Contributor
timestamp: June 02, 2021, 02:07:35 am
content: I'm thinking the level shofter/buffer IC is fried.You mean 5-6 mA from the VCC pin on the target connector? Yes, this is too much. This voltage is only used to power the output buffers. And this further indicates that the buffer is fried.

author: Kalcifer
author_rank: Regular Contributor
timestamp: June 02, 2021, 02:56:13 am
content: Quote from: ataradov on June 02, 2021, 02:07:35 amCould that cause the crazy glitching that I am seeing on the reset line?Quote from: ataradov on June 02, 2021, 02:07:35 amWhat I mean about the 5-6mA is that when I am probing the reset line with vcc tied to the power supply +3.3 and gnd tied to the power supply gnd, I am seeing a draw of 5 or so mA on my power supply, so I am guessing that the programmer is sinking the current, and not sourcing it.Quote from: ataradov on June 02, 2021, 02:07:35 amHow the heck would I have even managed that? how would I have fried the programmer? It only ever sees 3.3 volts, and I don't really disconnect or reconnect it ever. It just stays attached to the breadboard for testing. Is it a manufacturer defect possibly?If it is fried, how could I verify that for sure? I'm looking at the PCB, and everything seems on the outside, nothing burnt or anything.

author: ataradov
author_rank: Super Contributor
timestamp: June 02, 2021, 04:34:22 am
content: If it is just the power supply indicator, it may not be sensitive enough, 5 mA may be a very inaccurate number. So it may be nothing, unless you have a working unit to compare.I would probe around level shifters (and reset specifically) and check their inputs and direction control signals. If you see that all the inputs from the debugger side are stable, yet you get this noise on the target side. Check the power supply to the level shifter too, of course.They are 6-pin devices. There should be 5 or 6 of them in a row. Figure out which one goes to the reset pin and focus on it. Capture scope traces for all 6 pins.And looking at the board pictures, it looks like the same devices may be used to drive LEDs, in which case you have a couple spares. As long as you can do SMD soldering.