Originally, the RGB controller was implemented using AVR Xmega microcontroller. To keep things simple, it was ported to Arduino, because it's easier to understand for everyone.
- Arduino Uno R3 board was used as a controller.
- RGB is a common-anode 10mm LED, connected directly to Arduino PWM pins. Here, 820 Ohm resistors are used to limit the LED current. If you need higher power LED or e.g. 12V LED strips, you'd need to use some power transistors. Se e.g. this guide to learn why.
- Bluetooth is a cheap
HM-10 / MLT-BT05BT 4.0 module. Communicates over 3.3V, but needs 5V supply. (when powered with 3.3V, it enters the AT mode). A comprehensive guide to this module can be found here. The module has one custom BLE service (0xFFE0) with one characteristic (0xFFE1) for serial communication. - A resistor voltage divider is used on the
Arduino TX -> Bluetooth RXline to lower the input voltage from 5V to around 3.3V. Resistor ratio is 2k/1k.
The circuit:
To simplify the implementatnion as much as possible, some additional Arduino libraries were used:
- TimerOne - uses Timer 1 to generate regular interrupts every 1ms
- SerialCommands - to help parse commands received by bluetooth serial.
The code is pretty straightforward. The Bluetooth module is talking via SoftwareSerial on pins 2 and 4. Pins 3, 5 and 6 are PWM pins for RGB. After the startup sequence, the program waits for command in format RGB xxx yyy zzz\r\n where xxx, yyy and zzz are integers in range 0-255.
A simple linear fading functionality was implemented. It takes roughly 256ms for a value to go from 0 to 255. It is enough, when audio commands are sent with about 100ms interval.