i2c_slave.c

#define BUFFER_SIZE 10

enum SlaveMode {
    Receiving,
    Transmitting,
    Listening
} slaveMode = Listening;

uint8_t receivingBuffer[BUFFER_SIZE] = {0};
uint8_t receivingBufferDataSize = 0;

uint8_t transmittingBuffer[BUFFER_SIZE] = {0};
uint8_t transmittingBufferDataSize = 0;

void transmit(const uint8_t *data, uint8_t dataSize) {
    if (dataSize > BUFFER_SIZE) {
        dataSize = BUFFER_SIZE;
    }

    for (int i = 0; i < dataSize; ++i) {
        transmittingBuffer[i] = data[i];
    }

    transmittingBufferDataSize = dataSize;
}

void HAL_I2C_AddrCallback(I2C_HandleTypeDef *hi2c, uint8_t transferDirection, uint16_t addressMatchCode) {
    if (transferDirection == I2C_DIRECTION_RECEIVE) {
        slaveMode = Transmitting;
        transmittingBuffer[0] = 0x55;
        transmittingBufferDataSize = 1;
        HAL_I2C_Slave_Seq_Transmit_DMA(hi2c, transmittingBuffer, transmittingBufferDataSize, I2C_LAST_FRAME);
    } else {
        slaveMode = Receiving;
        HAL_I2C_Slave_Seq_Receive_DMA(hi2c, receivingBuffer + receivingBufferDataSize, 1, I2C_NEXT_FRAME);
    }
}

void HAL_I2C_ListenCpltCallback(I2C_HandleTypeDef *hi2c) {
    slaveMode = Listening;

    receivingBufferDataSize = 0;
    HAL_I2C_EnableListen_IT(hi2c);
}

void HAL_I2C_SlaveRxCpltCallback(I2C_HandleTypeDef *hi2c) {
    if (receivingBufferDataSize >= BUFFER_SIZE) {
        return;
    }
    receivingBufferDataSize++;

    if (slaveMode == Receiving) {
        HAL_I2C_Slave_Seq_Receive_DMA(hi2c, receivingBuffer + receivingBufferDataSize, 1, I2C_NEXT_FRAME);
    }
}

void HAL_I2C_SlaveTxCpltCallback(I2C_HandleTypeDef *hi2c) {
    transmittingBufferDataSize = 0;
}

void HAL_I2C_ErrorCallback(I2C_HandleTypeDef *hi2c) {
    HAL_I2C_EnableListen_IT(hi2c);
}