Recently I have ordered five more blue pills from Aliexpress required for my future projects. Its a great board but as you might know that this has wrong pullup resistor (R10=10k) at USB D+ line. The USB standard requires a 1.5k R pullup on D+.

The software hack which we discussed before is a good solution and it works 90% times. It might not work on some usb hub or you would need unplug and plug several times to make usb work.

In this tutorial, we will learn how to correct this mistake by replacing with correct USB pullup resistor on D+ line.


  • Hot air gun
  • 0603 size 1.5k resistor

Remove R10

You would need a hot air gun to remove R10 resistor. Its much easier to remove R10 by hot air gun.

wrong R10

replace R10 with 1.5k Resistor

I did not have 0603 size 1.5k resistors. I did salvage 2.2k resistor from a broken step up voltage converter. You can put some solder on R10 solder pads and solder new resistor on R10.

corrected pullup

Finally I got 1.5K resistors of size 0603 and fixed remaining four blue pills with it.