From DD-WRT Wiki

Contents 1 Permanent Fix 2 Workaround

The OM1P has a hardware watchdog that will reset the device every 5 minutes if it's not reset via a GPIO device.

[edit] Permanent Fix

install DD-WRT Micro_Redboot to disable the HW watchdog permanently

[edit] Workaround

After you got the route flashed you have 5 minutes to configure this.

Tested on:

• DD-WRT v24 Beta (08/03/07) std
• DD-WRT v24-sp2 (10/10/09) std

Go to your web interface add a custom script:

chdir / 
/sbin/gpio enable 3 

echo "1" >/proc/gpio/3_out 
echo "0" >/proc/gpio/3_out 

echo "1" >/proc/gpio/3_dir 
echo "0" >/proc/gpio/3_dir

Then enable Cron under management and add this line Code:

*/4  *  *   *   *   root  /tmp/custom.sh

Log into via console or web interface and restart cron:

stopservice cron && startservice cron

Not sure but i think you have to do this every time you restart the device.

Original hw-heartbeat.sh from Open-Mesh

#!/bin/sh 
# /sbin/hw-heartbeat.sh 
# send heartbeat to the hardware watchdog 

GPO="3" 
MCTL="4" 

[ "$(uci get node.general.hw_watchdog)" -eq 1 ] && { 
# i have no idea	
gpioctl dirout $GPO ; 
# set pin $GPO (3) to direction out? 
gpioctl clear $GPO 
# set pin 3 to logic 0 

sleep 1 
# wait one second/milli second? 

gpioctl set $GPO 
# set pin 3 to logic 1 
logger -st ${0##*/} 
"signaling to the hw-watchdog" 
# write something to the log 
} 
#

Source: Open-Mesh OM1P 5 minute hw-heartbeat.sh restart