Re: Communication to the STM32 fails -- something's broken
Posted: Mon May 02, 2016 3:12 am
I spent some time poking and prodding now that I've got another functional board to compare against. Observations:
1) double checked NRST is high (2.85v) on both boards as expected
2) double checked BOOT0 is low on both boards as expected
3) Voltage across C1 is 2.85v on both boards as expected
4) Voltage across C2 and C3 is 1.25V on the good board but 140mA and 100mA on the bad board
5) Continuity test shows the SWD connections are good from the debug connector to the STM
6) I've visually inspected both boards for any obvious problems and I discovered the power switch is completely gone on the bad board. It's been busted for a while now but had previously been mostly intact. Based on the schematic I don't see any reason for this to be related, right?
Observation #4 is possibly interesting but probably not: C2 and C3 are coming off the voltage regulator in the STM. The datasheet says the output of the voltage regulator should be 1.2v, and is enabled by default on this particular package (larger packages expose a pin to bypass the functionality). I guess all this means, though, is that the STM isn't booting properly.
1) double checked NRST is high (2.85v) on both boards as expected
2) double checked BOOT0 is low on both boards as expected
3) Voltage across C1 is 2.85v on both boards as expected
4) Voltage across C2 and C3 is 1.25V on the good board but 140mA and 100mA on the bad board
5) Continuity test shows the SWD connections are good from the debug connector to the STM
6) I've visually inspected both boards for any obvious problems and I discovered the power switch is completely gone on the bad board. It's been busted for a while now but had previously been mostly intact. Based on the schematic I don't see any reason for this to be related, right?
Observation #4 is possibly interesting but probably not: C2 and C3 are coming off the voltage regulator in the STM. The datasheet says the output of the voltage regulator should be 1.2v, and is enabled by default on this particular package (larger packages expose a pin to bypass the functionality). I guess all this means, though, is that the STM isn't booting properly.