Hello,
I am working on a custom board using a STM32F030K6T6. We are already in production and on like 15 parts over 4000, after that the product passed the electrical tests in production, and most of the time, after then, we tested it manually using a FTDI RS232 to establish a UART connexion, it appears that it stops communicating (so, after it first works well).
- There is nothing visible on the pcb and on the uC.
- Measurements shows that the uC is blocked in reset mode (voltage level is around 180mV, sometimes 240mV on nRST pin).
- I have made some measurements on the input power of the uC to identify if there is something wrong with the time taken to reach 3.3V, but nothing different from a working product.
- I have trying to read flash memory using st link utility, but it is not even able to connect to the target
- I have trying to reflash it but the connexion can not be made
- I have trying to make a short cut from the 3.3V to the nrst pin but it does not work
- I have trying to plug a 10kOhm resistor between boot0 and gnd (on 2 products which are blocked in reset mode) but it changes nothing
- I have removed the capacitor on Nrst pin, and it starts working !
- Then, I have put in place the same capacitor, at the same location, and it keeps on working ! the reset bug is gone, but not solving the issue...
I first thought it is something linked to the fact that we plug the FTDI cable to establish the communication, as maybe an ESD, but in this case, it wouldn't work again after the capacitor removal.
Here is the schematic:
So if you have any idea about what's going on, a design remark on the schematic, or best, already seen that, it would be really great and helpfull !
Thanks in advance,
