stm32f429 disco hardware problem.

[talha89]

Hey guys,

I seem to have accidentally bricked my stm32f429 disco board. By mistake i connected the external power supply while the st-link cable was connected to pc. I have done some troubleshooting. When i remove the ldd (JP3). All the leds light up no problem and the D2 diode has 4.8V and D3 which is connected to the regulator U1 has 3.3V. When i connect the ldd jumper back on the power led becomes very dim and the output of U1 goes down to 1.9V.

I have through the rusefi stm32f4 discovery repair guide http://rusefi.com/wiki/index.php?title=Hardware:stm32f4discovery_repair. But the solution to issue no. 5 is not given. Please let me know if i could provide you guys with any more details in order to zero down on the issue.

Regards

[kb1gtt]

Just to make sure I'm on the same page as you, you have gone through Step 1 and gotten to check point #5, then you had a problem with dim D1. Can you confirm that I'm not making wrong assumptions about the steps 1 to 4.
http://rusefi.com/wiki/index.php?title=Hardware:stm32f4discovery_repair#Check.28s.29_to_determine_what_solution_to_follow.

If you have not already done so and you can get your programming chip to boot up, you should update your programming chips firmware. Take note that when you do this it will likely take you something like 15 minutes while you wait for windows to decide what driver to use. The process works, but many of us have smashed our heads on our keyboards as we didn't happen to notice that windows was updating the driver.

I seem to recall I put the contact the forum note here because at this point I expect you have damaged pin input, the ESD diodes are probably shorted to GND causing an over current situation. However it's possible that other external / replaceable components could be the source of this short. I would not expect this from just being powered by USB vs normal power supply. I would expect this from a power supply that is much higher, or perhaps an ESD event.

I'm reasonably sure your discovery is toast. I expect this is at the point where you replace chips, probably the big STM32 chip itself. So I should ask, do you have the abilities / willingness to change the larger chip?

[talha89]

Yeah i followed the steps enlisted on the repair guide. When i remove the ldd (JP3) and power the board using the usb stlink port the com and pwr leds are solid red. But the solution to this issue is to replace the D3 diode. I have checked both D3 and D2 diodes and they are functioning properly. Also i forgot to mention that when i power the board from an external source using the 3V input pin, the blinky code executes properly but the leds are very dim and the supply voltage is 2.5V (output of U1)instead of 3.3V. Tried the same with 5V input pin and the board does not power on. I should be able to replace the chip, since i am used to building my own stm32 custom boards. But i jut absolutely want to be sure before i start ripping stuff apart .

[kb1gtt]

This is a good chance that it's just a decoupling cap. Especially if you provide 3V and it works. You might want to see if one of those caps gets hot. Perhaps try removing R26 and see if that make it work. I would expect messed up operation, but should at least boot such that it does things, even if they are wrong things, and not have dim LED's. You could also try removing L1 to see if those caps are buggered. If you not using chips like U9, you could also try removing them. Also you could always leave it plugged in for a while and see what gets hot, or what eventually fails more noticeably.

Cool you assemble your own boards. Might be worth noting this board. http://rusefi.com/forum/viewtopic.php?f=4&t=381

[talha89]

I think you are correct regarding the decoupling caps. i just tested the circuit for shorts and the VDD has been shorted to Vss . The STM32F429ZI chip get really hot when powered up also the power regulator gets very hot Confused as to how the chip still exectues the code properly. Replacing the decoupling caps should do the job yeah?

[AndreyB]

Please post your results if you choose to try it