Nucleo STM32F103RB : cannot blink a led on GPIO B3

[eLuigi]

Posted on May 15, 2017 at 20:37

Hi everybody,

I can't blink a led on GPIO B3 (PB3) port , the code works well on another ports like PB5 PA5... but not on PB3.

I have buy another nucleo board cause I was thinking I have an issue with my previous board but same issue on the new board. Anyone have a explanation.

FYI I need this port to emulate an aim board which use this port for a status led so...

Thanks for your help

Etienne

[Max · Accepted solution]

Posted on May 16, 2017 at 09:34

PB3 is the SWO pin and is connected to the on board STLink.

remove SB15 if you want to use it in your application.

You should have checked the schematic before buying a new board.

You can get it

http://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-eval-tools/stm32-mcu-eval-tools/stm32-mcu-nucleo/nucleo-f103rb.html

.

[AvaTar]

Posted on May 16, 2017 at 09:53

PB3 is the SWO pin and is connected to the on board STLink.

remove SB15 if you want to use it in your application.

While technically correct, I would never ever recommend that to an inexperienced user.

Else you have him back with more serious issues one hour later ...

[eLuigi]

Posted on May 16, 2017 at 21:33

Thank you for your answers, just two questions for my knowledge:

1- what is SB15? (yes I know I'm just new on nucleo)

2- Is it possible to desactivate the swo on the pb3 port and using another port connected to the stlink but on 'external device' connector?

[Tesla DeLorean]

Posted on May 17, 2017 at 00:25

It is a Solder Bridge (basically a jumper using solder), you'd need to use a soldering iron and a solder wick or sucker to remove the solder an open the circuit.

PB3 has defined functionality related to the debug interface, it can't use a different pin. The SWV (Serial Wire Viewer) it helps implement is optional. You will likely need to Remap the JTAG/SWD interface to use just the minimal SWDIO/SWCLK pins.

[waclawek.jan]

Posted on May 17, 2017 at 00:25

what is SB15?

SB stands for Solder Bridge, although in reality you'll find tiny 0-Ohm resistors soldered onto those which are by default shorted.

JW

PS. ST: in that UM1724, could be please table 10 fixed to properly indicate default state of all SBs which are not board-dependent?

[eLuigi]

Posted on May 17, 2017 at 08:34

Pretty clear, thank you for your help!