PwmOut example not working as expected

Mbed OS
,
1

Hi,

I’m new to mbed OS and have tried adapting the PwmOut example to run on an STM32F103 Blue Pill board to flash its LED on PC_13. The LED does flash, but it does so in a pattern of 4 slow flashes and 4 fast flashes.
What might be going on?

Edit: PwmOut works fine if I use a pin with hardware PWM support. PC_13 is not such a pin.

Thanks!

// main.cpp
//
// mbed-os.lib:
// https://github.com/ARMmbed/mbed-os/#565ab149819481224ab43f878c3921b14b11d180
//
// mbed compile --target BLUEPILL_F103C8 --toolchain GCC_ARM

#include "mbed.h"
PwmOut led(PC_13);

int main() {
// specify period first, then everything else
led.period(4.0f);  // 4 second period
led.write(0.50f);  // 50% duty cycle
while(1);          // led flashing
}

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2

Hello John,

On Mbed the pattern of 4 slow flashes and 4 fast flashes indicate a hard fault. Connect a serial monitor to the board (PA_2, PA_3 pins) to see run time error messages reported by the system.

3

Thanks for the tip. Here is the error, which seems to confirm that PWM is not supported on PC_13.

++ MbedOS Error Info ++
Error Status: 0x80010130 Code: 304 Module: 1
Error Message: pinmap not found for peripheral
Location: 0x800042B
Error Value: 0x2D
Current Thread: main Id: 0x20000DDC Entry: 0x8001553 StackSize: 0x1000 StackMem: 0x200015B0 SP: 0x200024FC 
For more info, visit: https://mbed.com/s/error?error=0x80010130&tgt=BLUEPILL_F103C8
-- MbedOS Error Info --