TIM 2 used while booting m4?

Official Hardware Mega GIGA R1 WiFi
1

When i flash my arduino Giga with 1 MB on M7 and 1 MB on M4, then boot the m4 using bootM4() and then print out the prescaler of timer TIM2, it is set to 239 (and a few other registers of TIM2 as well).

Is this intended? I could not find out why this is happening.

Steps to reproduce:

  1. use blink script example sketch, select 1MB flash split in arduino IDE and flash to M4 co-processor.
  2. use the following script and flash it with same memory split on M7:
#include <Arduino.h>

extern "C" uint32_t SystemCoreClock;

void setup() {
  Serial.begin(115200);
  bootM4();
   delay(4000); // important, takes a bit to take effect
  Serial.println(TIM2->PSC);
}
void loop() {
}

Expected result: TIM2->PSC should be 0

Actual result: TIM2->PSC is 239

Any idea what is going on here? Can I safely use TIM 2 for different purposes? I planned on using it in encoder mode to process a quadrature encoder.
So far, reconfiguring TIM 2 seems to work but I would like to have some clarity in order to not have my back bitten by this down the line.

2

Hi @tviehmann TIM2 is defined for us_ticker on M4 here ArduinoCore-mbed/cores/arduino/mbed/targets/TARGET_STM/TARGET_STM32H7/us_ticker_data.h at main · arduino/ArduinoCore-mbed · GitHub

1 Like
3

ah, that makes sense, thank you! In case someone else finds this, it also affects TIM5 for us_ticker on M7, good to know in case you plan to use them.

4

curious if you found a simple way to disable the us_ticker config that takes over these two timers. i would like to have them back for my own purposes if possible.
thanks,
Jeff

5

No, we have not looked into it further. We considered to patch the mbed os variant to use a timer that is not physically exposed on the giga, which at first glance looked kinda straightforward (but those also have less capabilities and I am not sure if this would cause issues somewhere). However, this adds significant complexity to our deployment and therefore we did not pursue this further.