PHPoC basically runs scripts when it boots up.
Therefore, it is possible that a P4S-342 cannot be escaped from infinite reboot when script contains system command such as "reboot".
To solve this problem, it is required to stop the running script.
Refer to the following.
Entering ISP mode
Make P4S-342 to enter ISP mode by supplying power while pressing FUNC button. In the ISP mode, you can access to PHPoC by PHPoC Debugger without running a script.
Connect to PHPoC
Connect a PC to PHPoC via a USB cable and connect to the port via PHPoC Debugger. A message window related with ISP mode will be popped up.
Reboot PHPoC by using "Reboot a product" menu in PHPoC Debugger. After rebooting, PHPoC stops running script even it is not in the ISP mode.
Correct source code
Correct the source code to prevent infinite reboot state.