A hardware abstraction layer (HAL) for the JLed library to use PCA9685 PWM drivers to control LEDs over I2C.
The PCA9685 is an I2C bus controlled LED/Servo controller with 16 individually controllable PWM channels. Each channel has a resolution of 12 bits, resulting in 4096 steps. All channels operate at the same fixed frequency, which must be in the range between 24Hz and 1526Hz.
The board operates at 3V to 5V, which is fed through the VCC pin. The V+ pin is optional and is used to power servos or LEDs with up to 6V. The V+ voltage can also be fed through the green terminal block and is routed to the red V+ pins.
Each of the yellow PWM outputs on the board has a 220 Ohms resistor in series, which allows the direct connection of a LED. The output level is the same as VCC.
SDA and SCL are the I2C data and clock pins. The OE pin is optional (and pulled down by default) and is used to quickly disable all outputs (by setting OE to high level).
The I2C address is by default 0x40 and can be changed by closing the A0 to
A5 pins using a soldering iron.
This library exposes two classes:
jled::PCA9685Hal- the Hardware Abstraction Layer for JLed for the PCA9685jled::JLedPCA9685- for convenience, a JLed for the the PCA9685Hal HAL is also provided
To use it, we first need to create a TwoWire instance for the I2C communication
and then an instance of the Adafruit_PWMServoDriver class to control the
PCA9685:
constexpr auto I2C_ADDRESS = 0x40; // I2C address of the PCA9685 board
auto i2c = TwoWire();
auto pwm = Adafruit_PWMServoDriver(I2C_ADDRESS, i2c);
auto led = jled::JLedPCA9685(jled::PCA9685Hal(15, &pwm)).Blink(250, 750).Forever();
void setup() {
pwm.begin();
}
void loop() {
led.Update();
}To simplify the construction of the jled::JLedPCA9685 objects, the
demo uses a helper:
constexpr auto I2C_ADDRESS = 0x40;
auto i2c = TwoWire();
auto pwm = Adafruit_PWMServoDriver(I2C_ADDRESS, i2c);
jled::JLedPCA9685 JLedPCA9685(jled::PCA9685Hal::PinType pin) {
return jled::JLedPCA9685(jled::PCA9685Hal(pin, &pwm));
}The construction then simplifies to
auto led12 = JLedPCA9685(12).Breathe(2000).Forever();The demo shows how to connect some LEDs to a PCA9685 and controls these LEDs with an Arduino Nano. Additionally, the builtin LED of the Arduino is also controlled by a JLed instance using the Arduino HAL.
When using this library with PlatformIO, the dependencies are automatically
resolved according to library.properties. Just add
lib_deps = JLedPCA9685-HAL to your platformio.ini file.
In the Arduino-IDE the dependencies must be configured manually. Make sure to add:
- JLedPCA9685-HAL (this library)
- JLed
- Adafruit PWM Servo Driver Library
in The Library Manager of the Arduino IDE, or manually run
$ arduino-cli lib install JLedPCA9685-HAL
$ arduino-cli lib install JLed
$ arduino-cli lib install "Adafruit PWM Servo Driver Library"Additionally the Arduino Wire library for the I2C communication is being used, wich is available by default in the Arduino Framework.
(C) Copyright 2022 by Jan Delgado
MIT