Global variables within an interrupt handler

Using Arduino Programming Questions
1

Hi New to forum and first post.. but here goes..

I am using the ESP32 Pico Kit and wanted to create a watchdog timer. Based on lib example I modified this code to see if I could access variables within an interrupt handler..

The timer triggers the interrupt at the correct time (so I have effectively a watchdog) but from within the interrupt handler I don't seem to be able to print out the msDuration global volatile variable that I was using to measure verify the timings of the code... (see below)

#include "esp_system.h"

const int wdtTimeout = 5000; //time in ms to trigger the watchdog
hw_timer_t *timer = NULL;

volatile long loopTime = 0;
volatile int msDuration = 0;

void IRAM_ATTR resetModule() {
ets_printf("Inside interrupt handler -> reboot with after a duration of %d (should be about 5000!)\n", msDuration);
esp_restart();
}

void setup() {
Serial.begin(115200);
Serial.println();
Serial.println("running setup");

timer = timerBegin(0, 80, true); //timer 0, div 80
timerAttachInterrupt(timer, &resetModule, true); //attach callback
timerAlarmWrite(timer, wdtTimeout * 1000, false); //set time in us
timerAlarmEnable(timer); //enable interrupt
}

void loop() {
Serial.println("running main loop");

timerWrite(timer, 0); //reset timer (feed watchdog)
long loopTime = millis();
long msDuration = 0;

for (int i=0;i<15;i++)
{
msDuration = millis() - loopTime;
Serial.printf("loop time is = %d on loop number %d\n", msDuration, i);
delay(1000); //simulate work
}
}

and the output from a run is below...

running setup
running main loop
loop time is = 0 on loop number 0
loop time is = 1001 on loop number 1
loop time is = 2001 on loop number 2
loop time is = 3001 on loop number 3
loop time is = 4001 on loop number 4
Inside interrupt handler -> reboot with after a duration of 0 (should be about 5000!)
ets Jun 8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)

why does the ets_printf get msduration as 0 ?? (see bold and underlined output above)?

Any suggestions or help much apprecated.

Thanks.

2

Inside an interrupt handler, interrupts are off. Printing things to the serial monitor uses interrupts and should be avoided. Inside the interrupt handler, you should just set a flag and then test/act on that flag in your main loop().

3

You have a local msDuration in loop(). Remove it.

4

Thanks both really appreciated you comments and help.. and as for me declaring a local msDuration in loop() - Doh!!!!!!