7-segment display driver over RS-232 using ATtiny2313

Building and burning the firmware

Dependencies: make gcc-avr avrdude

make program

If you've already changed the clock settings from the factory default, you'll also need to run make burn-fuse

Compiling Raspberry Pi GPIO software serial port on Raspbian

Two variables can be configured

• PIN is the number of the pin used for serial data (UART)
• BITLEN is the length of a bit in microseconds (733 works for 1200 bps)

These variables should be put into the appropriate -D parameters, and the commands below produce an executable called rpi that can be ran as an unprivileged user (the permissions are set to SUID root).

gcc rpi.c -o rpi -O3 -DPIN=... -DBITLEN=... -funroll-loops
sudo chown root:root rpi
sudo chmod +s rpi

The software serial port reads bytes from the standard input and emits them on the pin defined in PIN. BITLEN values under 1000 should be hand-tuned since the jitter on the Raspberry Pi without realtime mode can be high enough to make UART signals unreadable.