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

Revision 1 serial number 1 assembled and test code running successfully. Revision 2 designed, laid out, and sent to @laen for PCBing. PCBs and parts for rev 2 received.

Design Overview/Ideas

• Based around the ATtiny2313 ATtiny48 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.

• Add a green wire from the 3rd pin down on the left I/O connector to the last resistor in the first bank under the MCU
• Add a green wire from the 4th pin down on the left I/O connector to the first resistor pad in the second bank under the MCU
• This enables programming via the left connector (top to bottom):
  • 1 - GND
  • 2 - GND
  • 3 - MISO
  • 4 - /RESET
  • 5 - MOSI
  • 6 - SCK
  • 7 - VCC
  • 8 - VCC