Print stops after computer turned on or resumes from sleep mode
Micro controllers, like the AT Mega which is used on most RAMPs boards, can be controlled and upgraded via their USB port.
In order to upgrade the firmware on these boards the device must be placed in what's call "Device Firmware Upgrade" (DFU) mode. This will occur when one of the following events occurs.
- When a USB cable is inserted into a computer while plugged into the AT Mega.
- When a USB cable is inserted into an AT Mega while both the computer and micro controller are powered.
- When a computer resumed from hibernation (or deep sleep) while it is plugged into the AT Mega.
- When a computer is rebooted while it is plugged into the AT Mega.
- When the host sends down the wire a command to reboot and enter into DFU mode to the AT Mega.
If any of these events occur while your controller board is executing gCode commands it will immediately stop, reboot, and await for a new firmware. Once the timeout period is expired the original firmware begins executing - which means any knowledge of what it was doing prior to entering DFU mode is lost.
The fix for this problem is rather simple. If you have a LCD screen and your prints are reading from a thumb drive or SD Card make sure you unplug the USB from the controller board. There is really one reason to have a computer plugged in with this type of configuration - and that is if you are actively monitoring the print and attempting to debug a problem. If you do not have an LCD screen and rely upon a host to send the gCode to the micro controller then you need to actively go in a turn off any sleep/hibernation settings on your PC.