System Reset

Test Environments

	Hardware Comments	Nut/OS 4.8.0
Ethernut 1.3 H		Unknown bug: doesn't recognize reset cause
Ethernut 2.1 B		Unknown bug: doesn't recognize reset cause
Ethernut 3.0 E		Compiling Error (see discussion)
EIR 1.0 C	Set jumper JP1 to DBGU mode.	OK Binaries
Compiler: ARM-GCC 4.2.2 ; AVR-GCC 4.3.0

Source Code

<source lang="c">

1. include <dev/board.h>
2. include <dev/reset.h>
3. include <sys/timer.h>

1. include <stdio.h>
2. include <io.h>

int main(void) {

   int rc = NutResetCause();
   uint32_t baud = 115200;
   char *cause;
   int i;

   NutRegisterDevice(&DEV_DEBUG, 0, 0);
   freopen(DEV_DEBUG_NAME, "w", stdout);
   _ioctl(_fileno(stdout), UART_SETSPEED, &baud);

   switch (rc) {
   case NUT_RSTTYP_POWERUP:
       cause = "Powerup";
       break;
   case NUT_RSTTYP_WATCHDOG:
       cause = "Watchdog";
       break;
   case NUT_RSTTYP_EXTERNAL:
       cause = "External";
       break;
   case NUT_RSTTYP_SOFTWARE:
       cause = "Software";
       break;
   case NUT_RSTTYP_BROWNOUT:
       cause = "Brownout";
       break;
   default:
       cause = "Unknown";
       break;
   }
   printf("\nLast reset caused by %s (rc = %d)\n", cause, rc);

   for(i = 32; --i > 0 ;) {
       printf("\rNext reset in %d seconds", i);
       NutSleep(1000);
   }
   printf("\nReset\n");
   NutReset();
   printf("Reset failed\n");
   for (;;);

   return 0;

} </source>

Details

You can invoke a system reset by calling

<source lang="c"> NutReset(); </source>

This function will only return in case of a failure.

Use NutResetCause to determine the cause of the last reset.

<source lang="c"> rc = NutResetCause(); </source>

This function should be called at the very first beginning of your main program. It may return any of the following values:

• NUT_RSTTYP_POWERUP, if the reset was caused by powering up the system.
• NUT_RSTTYP_WATCHDOG, if the watchdog triggered the last reset.
• NUT_RSTTYP_EXTERNAL, if an external reset signal appeared like pressing a reset button.
• NUT_RSTTYP_SOFTWARE, if the reset was triggered by writing to a reset controller register.
• NUT_RSTTYP_BROWNOUT, if the reset was cause by low voltage detection.

Which code is actually returned depends on the capabilities of the CPU and the board design.

See also

• Watchdog Demo
• More Nut/OS ExamplesTemplate:Languages