Timeline for STM32F4 custom board design problem
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
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| Jan 26, 2021 at 17:44 | comment | added | jaskij | IIRC those F411s have almost all pins five volt tolerant, so if it's only 5V I2C it should work fine, although I have a feeling though that it's more luck than thorough consideration on OPs part. | |
| Jan 25, 2021 at 14:12 | comment | added | akohlsmith | One other thing I want to make sure I understand -- this new board with only the STM32, reset circuit and LED -- if you leave it disconnected for 15m and reconnect it to 3.3V only, does it work again? | |
| Jan 25, 2021 at 14:06 | comment | added | akohlsmith | Flux can certainly be conductive, although it's rarely an issue with modern, good fluxes. However it's an easy fix. Use lots of isopropyl alcohol and a stiff nylon brush (an old toothbrush is fine). Rubbing alcohol has too much water - won't hurt anything but will take much longer to dry. I can get 99% iso from any pharmacy here and it's very inexpensive. | |
| Jan 25, 2021 at 14:04 | comment | added | akohlsmith | "see the short circuit" -- how are you measuring and concluding that it is a short? Please do not use the ohms or short circuit setting on your VOM to measure the supply rails; many meters supply voltages way too high (9V or even more sometimes) to get a more accurate resistance measurement and this can cause permanent latchup on sensitive devices such as microcontrollers. Your meter may be smarter, use low voltage or limit current to a safe level to prevent such damage, but until we know for sure, don't do it. | |
| Jan 25, 2021 at 10:31 | comment | added | can | I also want to ask that is flux possible to be conductive?? Because I am using a lot of flux and I couldn't clean most of them and my data lines and pins of MCU are very close. In addition to that my flux is not in a good condition. | |
| Jan 25, 2021 at 6:48 | comment | added | can | LED2 is connected to the PC2 GPIO output pin of the MCU there is also a 220ohm resistor. I think that the problem is in the microcontroller. Because in second experiment there is nothing than STM32 on the board. However, you are right I2C line should not be pulled up to 5V. In addition to that in second experiment where only STM32 on the board. The current consumption was normal it was about 10-20mA. | |
| Jan 25, 2021 at 6:46 | comment | added | can | Thak you @akohlsmith for your detailed answer. Let me explain my last experiments on the PCB. For a second PCB I just mounted STM32F411RE, C5(Vcap), R9, C10, LED2, R11 and reset button. I did not solder any sensor, any voltage regulator etc. on second PCB. I used the power lines from ST-Link. I supplied only 3.3V to PCB. At the beginning I connected PCB via SWD to my computer and loaded simple LED blink program and everything works fine for a couple of minutes. After that I lost connection with PCB via ST-Link. I removed the power pins and see the short circuit. | |
| Jan 25, 2021 at 1:33 | history | answered | akohlsmith | CC BY-SA 4.0 |