qmk_firmware icon indicating copy to clipboard operation
qmk_firmware copied to clipboard

Published 20 hours ago • verified publisher icon qmk

Can't the two IOs of B2 and A9 of the STM32F401 development board be used on the qmk, and cannot be used in the matrix. Is there any special usage or where do I need to set it up separately?

Open jeromeli002 opened this issue 2 years ago • 2 comments

Can't the two IOs of B2 and A9 of the STM32F401 development board be used on the qmk, and cannot be used in the matrix. Is there any special usage or where do I need to set it up separately? image

jeromeli002 avatar Sep 08 '22 14:09 jeromeli002

Have you read the documentation about BlackPills? Most of that page is also applicable to the F401 model.

lesshonor avatar Sep 08 '22 14:09 lesshonor

PA9-PA12 are shared with USB connection pins. So they can't be used for key matrix fo QMK.

OTG_FS_VBUS is subtle to be noticed but this is USB OTG I suppose.

I learned this hard way.

Unusable pins

  • Pins A11 and A12 are not useable because they’re used for USB connection, and cannot be shared. In theory, these pins can be used. However, doing so may disable USB connectivity, outright, if used for anything other than a USB port
  • Pin B2 is used by BOOT1 and cannot be used, without causing problems.
  • VBAT is not a usable pin.
  • NRST is not a usable pin.

osamuaoki avatar Sep 13 '22 09:09 osamuaoki