We saw the issue in which the micro was not starting. We had powered up the device and the application firmware was running but the LEDs that were flashing suddenly stopped. We tried re-powering and found that the MCU reset was low (~200mV). What conditions could cause the reset line to be held low? The code that we saw this issue on was written by our CM for the hardware and we do not have the complete source so it is “black box” as to what the code is doing. I brought the unit back to my desk to try to reflash the unit and captured the below log. After clicking the toggle reset button the re-flash was successful and the application is running again.
[5/10/2017, 3:33:53 PM] [ERROR] CS_DAP_0: Error connecting to the target: (Error -1170 @ 0x0) Unable to access the DAP. Reset the device, and retry the operation. If error persists, confirm configuration, power-cycle the board, and/or try more reliable JTAG settings (e.g. lower TCLK). (Emulation package 6.0.576.0) No connection possible. This could be caused by the device having gone to low power mode and disabling JTAG PINs. You have the option to either toggle reset or try to use SWD instead.
[5/10/2017, 3:33:59 PM]
[5/10/2017, 3:33:59 PM]
[5/10/2017, 3:33:59 PM]
[5/10/2017, 3:34:00 PM] [INFO] CORTEX_M4_0: Flash Programmer: Erasing main memory
[5/10/2017, 3:34:00 PM] [INFO] CORTEX_M4_0: Flash Programmer: Writing 9448 bytes to flash memory 0x00000000
[5/10/2017, 3:34:01 PM] [SUCCESS] Program Load completed successfully.
