75XX Watchdog

From Technologic Systems Manuals

By default the watchdog is fed by ts7500ctl. This way if userspace, the kernel, or the FPGA communication has any issue the board will reboot. For many applications this may be enough, but you can tailor this more specifically to your application by feeding the watchdog on your own criteria. The watchdog feed register is write-only. Valid write values are:

Value Result
0 feed watchdog for another .338s
1 feed watchdog for another 2.706s
2 feed watchdog for another 10.824s
3 disable watchdog

Watchdog by default comes out of reset armed for .338 seconds. TS-BOOTROM firmware feeds for 10.824 and OS code has 10.824 seconds to take over. If you would like to run your own watchdog you will need to kill ts7500ctl when switching to your own application. You can feed the watchdog from your application by poking a register:

// Compile with gcc filename.c -o watchdog
#include <stdio.h>
#include <unistd.h>
#include "sbus.h"

int main(int argc, char **argv)
{
        // This is an example of feeding the watchdog for 10s
        for (;;) 
        {
                sbuslock();
                sbus_poke16(0x74, 2);
                sbusunlock();
                sleep(5); // Sleeping half of the 
                          // feeding time is usually a safe value
        }

        return 0;
}