Software reset

Forum 2005-2010 (read only) Software Troubleshooting
1

Is there a command to reset the arduino from within a programme? It'd be quite convenient now and again.

2

This topic has come up a few times. This is my understanding of resetting...

  • Don't. Figure out what's wrong and fix it.
  • It is possible to "reset" by jumping to address zero. This does NOT reset the hardware. It restarts the Sketch.
  • With some external circuitry it is possible to perform a hardware reset by setting an output pin high.
  • Letting the watchdog expire will reset the processor but the board may get caught in an infinite loop within the bootloader. A very long timeout may work.
3

How does one jump to address zero?

There's nothing wrong, it'd save me time if I could restart the sketch.

Poor programming technique I know, but I'm new to this :wink:

4 
asm volatile ("jmp 0x0000");

Packaged in a function might be a good idea...

void software_Reset() // Restarts program from beginning but does not reset the peripherals and registers
{
  asm volatile ("  jmp 0");  
}
5

Thanks, I'll give it a go.

6

No need for any assembler:
just declare
void (*restart)(void) = 0;

then call restart();

like any other function.

But it's still not a reset

7

...more of a "restart". :wink:

8

more of a "restart"

9

For sure it's a restart.

However before one uses it one should review their setup function carefully to see what effect that is going to have on the sketch. Setup function is meant to only run once and having it execute again via a 'restart' may cause some library initialization problems being that you are 'restarting' libraries without the hardware being in a know reset condition. Maybe not a problem most of the time, but really it's about understanding your program structure and not allowing a situation where you need to 'restart'. Relying on a software restart is a poor programming practice and is best not even being learned by a beginner as bad habits can be hard to quit over time. :wink:

Lefty