Part list

• 1x AVR atmega48
• 1x max232 chip
• 4x diode (for the diode bridge)
• 16x 220ohm resistor
• 1x 10k resistor
• 1x 7805 voltage regulator
• 1x 110vac -> 9vac transformer
• 1x 8mhz crystal
• 8x 3mm green led
• 8x 3mm red led
• 1x 470uf capacitor
• 1x 10uf capacitor
• 2x 22pf capacitor (crystal)
• 5x 1uf capacitor (charge pump for the max232)
• 1x female DB9 connector
• 1x speaker (ripped from an alarm clock)
• 1x small switch (enable/disable the speaker)
• telephone wire for the serial connector
• plexiglass

Schema

This schema has been made using GEDA (GNU Eda Schematic Editor).

Protocol

All commands are 1-byte wide. Each command can adress at most a line of led (2 led, one green and one red).

The settings for the serial port must be 8N1 (8 bit, no parity and a stop bit) without hardware flow control. All commands are sent sequentially.

If both slowflash and fastflash bits are set, then the remaining of the command is ignored (the index is ignored, and no leds are updated), and the speaker alarm starts.

0 0 0 0 0 0 0 0
|     | | | | +-- fastflash
|     | | | +---- slowflash
|     | | +------ red led on
|     | +-------- green led on
+-----+---------- led index (0..7)

Files

• Source file for the avr micro-controller
• Firmware (.hex format)
• Complete package, including oavrl and the build script

Images