i2c_slave_handler_t

I2C slave event handler The event handler will run from the I2C ISR, so it should return quickly (under 25 us at 400 kb/s). Avoid blocking inside the handler and split large data transfers across multiple calls for best results. When sending data to master, up to i2c_get_write_available() bytes can be written without blocking. When receiving data from master, up to i2c_get_read_available() bytes can be read without blocking.