SeriAlpha

SeriAlpha is a small backpack for alphanumeric LEDs (16 segment, specifically). It will accept I2C/SPI communications, and control the LED display attached to it.

Project Status

Schematic/board done, BOM on file at Digikey, board and parts have been ordered and have arrived.

Design Overview/Ideas

• Based around the ATtiny2313 in a QFN20 package
• Individual transistors for each segment, so it will support all segments on at once and nifty things like PWMing segments
• Built in character generator, so you can just tell the board what letter/number to display.
• Targeting the SparkFun-sold 16segment LED displays

Revision 1 Design Issues

• Unable to disable RESET pin due to silicon errata, so one segment won't work. - Fixed by switching to ATmega48 in revision 2.
• No bypass caps on PCB - Fixed in revision 2.
• Board could be smaller if MCU moved to bottom of board - Fixed in revision 2.
• Resistor networks and dual-transistors would make assembly much easier - Fixed in revision 2.

Programming Revision 1 Boards

Revision 1 boards were accidentally missing a programming header.

• MOSI - 5th pin down on I/O headers
• MISO - Tap a wire off the last resistor in the first bank under the MCU
• SCK - 6th pin down on I/O headers
• RESET - Tap a wire off the unstuffed first resistor pad in the second bank under the MCU