hardware_watchdog

Functions

void watchdog_reboot (uint32_t pc, uint32_t sp, uint32_t delay_ms)
 Define actions to perform at watchdog timeout. More...
 
void watchdog_start_tick (uint cycles)
 Start the watchdog tick. More...
 
void watchdog_update (void)
 Reload the watchdog counter with the amount of time set in watchdog_enable.
 
void watchdog_enable (uint32_t delay_ms, bool pause_on_debug)
 Enable the watchdog. More...
 
bool watchdog_caused_reboot (void)
 Did the watchdog cause the last reboot? More...
 
bool watchdog_enable_caused_reboot (void)
 Did watchdog_enable cause the last reboot? More...
 
uint32_t watchdog_get_count (void)
 Returns the number of microseconds before the watchdog will reboot the chip. More...
 

Detailed Description

Hardware Watchdog Timer API

Supporting functions for the Pico hardware watchdog timer.

The RP2040 has a built in HW watchdog Timer. This is a countdown timer that can restart parts of the chip if it reaches zero. For example, this can be used to restart the processor if the software running on it gets stuck in an infinite loop or similar. The programmer has to periodically write a value to the watchdog to stop it reaching zero.

Example

#include <stdio.h>
#include "pico/stdlib.h"
int main() {
printf("Rebooted by Watchdog!\n");
return 0;
} else {
printf("Clean boot\n");
}
// Enable the watchdog, requiring the watchdog to be updated every 100ms or the chip will reboot
// second arg is pause on debug which means the watchdog will pause when stepping through code
watchdog_enable(100, 1);
for (uint i = 0; i < 5; i++) {
printf("Updating watchdog %d\n", i);
}
// Wait in an infinite loop and don't update the watchdog so it reboots us
printf("Waiting to be rebooted by watchdog\n");
while(1);
}
void watchdog_update(void)
Reload the watchdog counter with the amount of time set in watchdog_enable.
Definition: watchdog.c:25
bool watchdog_caused_reboot(void)
Did the watchdog cause the last reboot?
Definition: watchdog.c:99
void watchdog_enable(uint32_t delay_ms, bool pause_on_debug)
Enable the watchdog.
Definition: watchdog.c:70
void stdio_init_all(void)
Initialize all of the present standard stdio types that are linked into the binary.
Definition: stdio.c:270

Function Documentation

◆ watchdog_caused_reboot()

bool watchdog_caused_reboot ( void  )

Did the watchdog cause the last reboot?

Returns
true If the watchdog timer or a watchdog force caused the last reboot
false If there has been no watchdog reboot since the last power on reset. A power on reset is typically caused by a power cycle or the run pin (reset button) being toggled.

◆ watchdog_enable()

void watchdog_enable ( uint32_t  delay_ms,
bool  pause_on_debug 
)

Enable the watchdog.

Note
If watchdog_start_tick value does not give a 1MHz clock to the watchdog system, then the delay_ms parameter will not be in microseconds. See the datasheet for more details.

By default the SDK assumes a 12MHz XOSC and sets the watchdog_start_tick appropriately.

This method sets a marker in the watchdog scratch register 4 that is checked by watchdog_enable_caused_reboot. If the device is subsequently reset via a call to watchdog_reboot (including for example by dragging a UF2 onto the RPI-RP2), then this value will be cleared, and so watchdog_enable_caused_reboot will return false.

Parameters
delay_msNumber of milliseconds before watchdog will reboot without watchdog_update being called. Maximum of 0x7fffff, which is approximately 8.3 seconds
pause_on_debugIf the watchdog should be paused when the debugger is stepping through code

◆ watchdog_enable_caused_reboot()

bool watchdog_enable_caused_reboot ( void  )

Did watchdog_enable cause the last reboot?

Perform additional checking along with watchdog_caused_reboot to determine if a watchdog timeout initiated by watchdog_enable caused the last reboot.

This method checks for a special value in watchdog scratch register 4 placed there by watchdog_enable. This would not be present if a watchdog reset is initiated by watchdog_reboot or by the RP2040 bootrom (e.g. dragging a UF2 onto the RPI-RP2 drive).

Returns
true If the watchdog timer or a watchdog force caused (see watchdog_caused_reboot) the last reboot and the watchdog reboot happened after watchdog_enable was called
false If there has been no watchdog reboot since the last power on reset, or the watchdog reboot was not caused by a watchdog timeout after watchdog_enable was called. A power on reset is typically caused by a power cycle or the run pin (reset button) being toggled.

◆ watchdog_get_count()

uint32_t watchdog_get_count ( void  )

Returns the number of microseconds before the watchdog will reboot the chip.

Returns
The number of microseconds before the watchdog will reboot the chip.

◆ watchdog_reboot()

void watchdog_reboot ( uint32_t  pc,
uint32_t  sp,
uint32_t  delay_ms 
)

Define actions to perform at watchdog timeout.

Note
If watchdog_start_tick value does not give a 1MHz clock to the watchdog system, then the delay_ms parameter will not be in microseconds. See the datasheet for more details.

By default the SDK assumes a 12MHz XOSC and sets the watchdog_start_tick appropriately.

Parameters
pcIf Zero, a standard boot will be performed, if non-zero this is the program counter to jump to on reset.
spIf pc is non-zero, this will be the stack pointer used.
delay_msInitial load value. Maximum value 0x7fffff, approximately 8.3s.

◆ watchdog_start_tick()

void watchdog_start_tick ( uint  cycles)

Start the watchdog tick.

Parameters
cyclesThis needs to be a divider that when applied to the XOSC input, produces a 1MHz clock. So if the XOSC is 12MHz, this will need to be 12.