MCU Reset line is permanently low

helena-project / imix

imix Low-Power IoT Research Platform

32 stars 6 forks source link

MCU Reset line is permanently low #3

Closed alevy closed 7 years ago

alevy commented 8 years ago

Cause

Reset line on the FTDI side is shorted to ground in an internal layer. :(

Workaround

Cut the trace as shown below so that the FTDI side is disconnected from the MCU side. This will allow the MCU to be programmed using a JLink.

cut_reset

shaneleonard commented 8 years ago

@alevy It turns out this issue was not due to the diode, but actually due to RESET being shorted to ground near the FTDI chip. The internal ground plane near the FTDI does not have the proper isolation, so it appears to have shorted to the RESET vias. Fortunately, however, this means that the board can actually be completely programmed and powered without adding or removing any components. All that is needed is to cut the trace as shown above.