Recently I have designed my custom PCB board, which includes a SAMD21E18A. Unfortunately, I am having trouble with programming. I am enclosing the schematic (please ignore the quality of the schematic, it is still a work in progress). It should also be noted that all other active components on the board were desoldered and only MCU, LDO, programming header, and a couple of passive components are present.
For programming, I am using the Microchip Studio with ATMEL ICE programmer. My problem is as follows:
- SOMETIMES, I am unable to read the device signature. However, the target voltage is stable at 3.3V. It seems to read the signature just sometimes, usually the signature is read a couple of times after the MCU is powered, and then it suddenly stops responding.
- Since I could not resolve this problem (I am unfortunately unable to test the programmer on a different board), I tried to conduct some measurements. One unexpected thing I could measure is a voltage of 0.6-0.7V at the RESET line while the ATMEL ICE is connected.
To conclude, I would like to ask if anyone has ever experienced similar behavior (the MCU is clearly not dead since I am able to read the signature once in a while). Do you think there is a chance my programmer/debugger ATMEL ICE may be faulty?