Pigeon has two watchdogs. The first watchdog is inside SoC and the second is chip STWD100 connected to the GPIOs.

Broadcom SoC watchdog

Broadcom SoC has a built-in hardware watchdog timer. By default Broadcom SoC watchdog is on. You can check the status of the watchdog:

dmesg | grep watchdog

If you want to check watchdog service:

systemctl status watchdog.service

If you have to change the configuration of watchdog, edit /etc/watchdog.conf file.

Watchdog chip

Pigeon has watchdog chip STWD100 controlled by GPIO, according to the table below.

Table 1. Watchdog GPIO

Enable watchdog - EN GPIO5
Watchdog input - WDI GPIO44

Enable signal is active low. By default enable signal is high (GPIO5 = 1), so the watchdog is not active.

If EN signal is active then the Watchdog input (WDI) has to be toggled within the watchdog timeout period (1 second), otherwise the reset signal is asserted. The watchdog timer is cleared either:

  • by toggling WDI input high to low,
  • by a pulse on enable pin EN,
  • by a transition on watchdog output (reset).

The pulses on WDI input with a duration of at least 1 µs are detected.