To create an I2C device, first call i2c_init, passing in an i2c_config_t struct. This struct defines the SCL/SDA pins, the I2C device address, and the connect/read/write/disconnect callbacks.
i2c_init
i2c_dev_t i2c_init(i2c_config_t *config)
config argument defines the pins, address, and callbacks for the I2C device. It contains the following fields:
Listen for requests matching the given I2C address (7-bit). To listen for all requests, set to 0
Called when the chip is addressed on the I2C bus
Called when the microcontroller wants to read a byte of data from your chip
Called when the microcontroller writes a byte to your chip
Called when the microcontroller disconnects from your chip
Data that will be passed in the first argument of the callbacks
connect, read, write, disconnect) are optional. They all use the user_data pointer as their first argument.
Note: i2c_init can only be called from chip_init(). Do not call it at a later time.
Example
bool on_i2c_connect(void *user_data, uint32_t address, bool read) {
// `address` parameter contains the 7-bit address that was received on the I2C bus.
// `read` indicates whether this is a read request (true) or write request (false).
return true; // true means ACK, false NACK
}
uint8_t on_i2c_read(void *user_data) {
return 0; // The byte to be returned to the microcontroller
}
bool on_i2c_write(void *user_data, uint8_t data) {
// `data` is the byte received from the microcontroller
return true; // true means ACK, false NACK
}
void on_i2c_disconnect(void *user_data) {
// This method is optional. Useful if you need to know when the I2C transaction has concluded.
}
static const i2c_config_t i2c1 {
.address = 0x22,
.scl = pin_init("SCL", INPUT_PULLUP),
.sda = pin_init("SDA", INPUT_PULLUP),
.connect = on_i2c_connect,
.read = on_i2c_read,
.write = on_i2c_write,
.disconnect = on_i2c_disconnect,
.user_data = chip,
};
