Bluepill: Will not power up via USB

20170123_101108.jpg (184.7 KiB) Viewed 934 times

I had 3 boards with not working USB connector, which worked after I soldered them…

The USB connector would be my guess too. Also what on earth are those splashed blobs of solder next to the boot pins on the back of the board all about.
If it isn’t the USB connector then my next guess would be the voltage regulator, or… you powered up using USB *and* had the 3v3 connected from the ST-Link at the same.. That seems to cause the voltage regulator to take a fit or even pop. Check to see if the regulator is getting 5V in, and spitting 3v3 out.

stevestrong wrote:I had 3 boards with not working USB connector, which worked after I soldered them…

ahull wrote:The USB connector would be my guess too. Also what on earth are those splashed blobs of solder next to the boot pins on the back of the board all about.
If it isn’t the USB connector then my next guess would be the voltage regulator, or… you powered up using USB *and* had the 3v3 connected from the ST-Link at the same.. That seems to cause the voltage regulator to take a fit or even pop. Check to see if the regulator is getting 5V in, and spitting 3v3 out.

johnwigley wrote:ahull wrote:The USB connector would be my guess too. Also what on earth are those splashed blobs of solder next to the boot pins on the back of the board all about.
If it isn’t the USB connector then my next guess would be the voltage regulator, or… you powered up using USB *and* had the 3v3 connected from the ST-Link at the same.. That seems to cause the voltage regulator to take a fit or even pop. Check to see if the regulator is getting 5V in, and spitting 3v3 out.

Assuming the 5V doesn’t even appear on the 5V pin adjacent to the LEDs, then the fault is either the connector or the via that passes the track from the top (USB connector side) to the bottom, and on to the 5V pin. Buzz it out with your continuity tester. My second bet however based on the symptoms is that the 0V side is not connected, hence the weird half a volt floating voltage. The soldering looks OK in the picture, so I suspect the USB connector or more likely your USB cable since the problem affects all three boards.

EDIT: .. and if your soldering skills are up to it, put some more solder on the tabs that hold the USB connectors to the board. This is a well known weakness. The USB connectors are easily parted from the board anyway, but the solder on those tabs on the one in the pictures is almost non-existent.

ahull wrote:

EDIT: .. and if your soldering skills are up to it, put some more solder on the tabs that hold the USB connectors to the board. This is a well known weakness. The USB connectors are easily parted from the board anyway, but the solder on those tabs on the one in the pictures is almost non-existent.

Thank you all so much for the help and advice.

I took leave of my senses, and decided to attempt to resolder the micro usb connector, and by some miracle all three of the boards are now powering up, and two of the three successfully enumerated as Maple DFU devices, and I flashed a test ECC routine which they both ran successfully and re-enumerated as serial ports! Success, though now I have to figure out how you flash them a second time as they appear as serial ports rather than DFU devices, though I’m sure there’s a FAQ on dealing with that.

The third board which is one of the batch of two from the same supplier, rather than the single one from a different supplier, is powering up and running fine BUT appears as an unknown USB device.The STM32duino boot loader flashes it’s LEDs correctly, and the board runs code uploaded through the STlink fine.

I’ve checked continuity through a cut off microusb cable, and tested that the cut off microusb cable’s wires are connected to PA12 & PA11, and that ground, and 5v are also connected. Further more, I’ve checked that the 10k (should be 1.5k according to USB specs, but well known Blue Pill issue) pull up resistor is connected correctly as well. The other two boards both have 10k pullups and they enumerate and program fine, so evidently the USB hub I’ve got isn’t strict.

Lastly I’ve checked that there aren’t any shorts between the USB pins. So it seems to me that the only thing left to check is whether or not PA11 & PA12 are actually connected to the MCU. For that I suppose I can write a test program that waggles the pins up and down and see if that appears on the PA11 & PA12 breakout.

Is there anything else I’m missing in terms of a diagnostic process on this one remaining board? I know the boards functional and working apart from the USB, so it seems to me that I’ve conducted all the USB connectivity tests possible already, with the exception of confirming that PA11/PA12 are actually attached to the MCU?

Thanks once again for the assistance, it’s much appreciated.

johnwigley wrote:

… now I have to figure out how you flash them a second time as they appear as serial ports rather than DFU devices, though I’m sure there’s a FAQ on dealing with that.

RogerClark wrote:johnwigley wrote:

… now I have to figure out how you flash them a second time as they appear as serial ports rather than DFU devices, though I’m sure there’s a FAQ on dealing with that.