SPI Module

Note

The SPI Module contains wrappers for the controller’s SPI interface.
Doxygen:

Features

There are a few pre-defined SPI interfaces:

  • SPI_Sensor: Connected to the on board sensors

  • SPI_Touch: Connected to the LCD Touch controller

Sending Data

The following code demonstrates how to set a register of the 6-Axis sensor by sending data directly to it.

// Set Chip Select here

// Write register address and data to sensor
uint8_t data[2] = { /* Register: */ 0x4E, /* Data: */ 0x0F };
if (R_SUCCESS(SPI_Write(SPI_Sensor, data, sizeof(data)))) {
    // Successfully sent data
}

// Unset Chip Select here
result_t SPI_Write(SPI_Handle_t handle, const uint8_t *buffer, size_t size)

Writes data to the SPI interface.

Parameters

  • buffer – Buffer to send data from

  • size – Buffer size

Returns

Status result

Receiving Data

The following code shows how to directly read data from e.g a RAM connected over SPI which doesn’t need any setup commands.

// Read data
uint8_t data[4] = { };
if (R_SUCCESS(SPI_Read(SPI_RAM, data, sizeof(data)))) {
    // Successfully read data
}
result_t SPI_Read(SPI_Handle_t handle, uint8_t *buffer, size_t size)

Reads data from the SPI interface.

Parameters

  • buffer – Buffer to store received data in

  • size – Buffer size

Returns

Status result

Sending and receiving data simultaneously

Many sensors and other more complex ICs connected over SPI first expect the address of the register that should be read to be sent before reporting back that register’s value.

Important

Since we’re writing and reading data at the same time, while sending out the first byte of address register, the sensor doesn’t repond yet so we’re reading a 0x00 byte. After the address is sent, since we want to receive data from the sensor now, the clock needs to be generated again for another byte. That’s why we have to send two bytes even though we only need to send one byte and receive one byte. Since the first byte of the receive buffer has been filled already too now, the actual data from the sensor can be found in the second position of the receivedData array.

                    00     01
Send Buffer    : | 0xF5 | 0x00 |
Receive Buffer : | 0x00 | 0x42 |

// Set Chip Select here

// Write WHO_AM_I register address and data to sensor and at the same time receive the sensor's answer
uint8_t registerAddress[2] = { /* Register: */ 0xF5, 0x00 };
uint8_t receivedData[2] = { 0x00, 0x00 };
if (R_SUCCESS(SPI_WriteRead(SPI_Sensor, registerAddress, receivedData, sizeof(registerAddress)))) {
    // Successfully sent and received data

    if (receivedData[1] == 0x42) {
        LOG_Info("Received correct device ID!");
    }
}

// Unset Chip Select here
result_t SPI_WriteRead(SPI_Handle_t handle, uint8_t *read_buffer, const uint8_t *write_buffer, size_t size)

Writes and reads data simultaneously to/from the SPI interface.

Parameters

  • read_buffer – Buffer to read data into

  • write_buffer – Buffer to send data from

  • size – Buffer size

Returns

Status result