A friend of mine had decided to build his own DVD/Hard disk recorder based on a PC with Linux and a TV card. This turns out to be a very cost-effective and future-proof solution that allowed to add many features. However it had also one disadvantage : the PC had to be switched on before the recording would start. Not very power friendly. Some experimenting showed that it was possible to turn on the PC using a the 'Wake-On-LAN' feature in the BIOS. Having one PC switch on another was obviously nonsense, so the idea grew to develop a power-friendly, microcontroller based little appliance that could send a 'Wake-On-LAN' signal to the PC at predefined times.The appliance we built is based on a microcontroller (PIC 18F458) with an extra Ethernet interface. Via this interface the device will receive commands from a host computer. These commands allow the user to specify at which times which computer has to be turned on, sort of an alarm clock with repetitive alarms. WOLL-Y will then issue so called 'Wake-On-Lan' Magic packets at the preset times and send them to the desired computer (identified via its MAC address). To allow WOLLY to determine the time it has a battery backed up real time clock. All configuration is stored in non-volatile RAM (either EEPROM or battery backed up RAM). To allow monitoring of the health state of WOLLY, the device has a status led and will send broadcast UDP packets at preset intervals containing its basic settings.
The PC user interface is written in Qt4 and automatically finds WOLLY on the LAN (by looking for the packets WOLLY broadcasts) and then allows to read the current config and add/remove or change entries in the table.
More detailed information, the circuit, the PC software and firmware can be found [HERE]
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