swabang

A minimal starter kit for programming WS2812b LEDs with avr-libc on the Arduino Uno/ATmega328P microcontroller.

Includes:

• Assembly procedures for bit-banging the WS2812b data protocol
• Makefile for building and flashing the Arduino Uno ROM

Prerequisites

You will require the following:

• avr-libc
• avr-gcc
• avr-objcopy
• avrdude

You may need to add yourself to the uucp group to read/write from/to serial ports:

$ usermod -a -G uucp yourself

Usage

Choose an I/O port and bit number from <avr/iom328p.h>. This example assumes bit 0 of port B is chosen (pin 8 on the Uno R3).

Assemble procedures for the WS2812b data protocol:

$ make clean; make SWABANG_BIT=PORTB0 SWABANG_PORT=PORTB
$ file swabang.o
swabang.o: ELF 32-bit LSB relocatable, Atmel AVR 8-bit, version 1 (SYSV), not stripped

Write an entry point defining main:

$ echo '#include <avr/io.h>
> #include <stdint.h>
>
> int main()
> {
>     DDRB |= _BV(DDB0);
>     uint8_t buf[12] = { 0, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1 };
>     ws2812b_reset();
>     ws2812b_send(buf,12);
> }' > main.c

Forward declarations for the ws2812b procedures will automatically be included into your program. See swabang.h for a list of available procedures.

Build the application and flash it onto the Arduino. Here we assume the device file /dev/ttyACM0 has been adequately permissioned and is connected to the Arduino's serial port:

make flash MAIN_FILE=main.c AVRDUDE_PORT=/dev/ttyACM0