spi-bcm2711 driver example

The spi-bcm2711 driver also implements the following functions:

void bcm2711spi_drvinfo(const void *const hdl, spi_drvinfo_t *info)

• Implements the drvinfo() function in the spi_funcs_t structure.
• Gets the SPI driver information.
• Arguments:
  • hdl — The handle of the low-level module returned by spi_init().
  • info — A pointer to store the SPI driver information.

void void bcm2711spi_devinfo(const void *const hdl, const spi_dev_t *const spi_dev, spi_devinfo_t *const info)

• Implements the devinfo() function in the spi_funcs_t structure.
• Obtains the SPI device information.
• Arguments:
  • hdl — The handle of the low-level module returned by spi_init().
  • spi_dev — A pointer to the SPI device structure.
  • info — A pointer to store the SPI driver information.

int bcm2711spi_dmaxfer(void *const hdl, spi_dev_t *spi_dev, dma_addr_t *addr, const uint32_t tnbytes, const uint32_t rnbytes)

• Implements the dma_xfer() function in the spi_funcs_t structure.
• Initiates a DMA transaction.
• Arguments:
  • hdl — The handle of the low-level module returned by spi_init().
  • spi_dev — A pointer to the SPI device structure.
  • addr — A pointer to the DMA address structure.
  • tnbytes — The number of transmit bytes.
  • rnbytes — The number of receive bytes.
• Returns:
  • EOK — Success.
  • errno — An error occurred.

int bcm2711_dma_allocbuf(void *const hdl, dma_addr_t *addr, const uint32_t len)

• Implements the dma_allocbuf() function in the spi_funcs_t structure.
• Allocates a DMA buffer.
• Arguments:
  • hdl — The handle of the low-level module returned by spi_init().
  • addr — A pointer to the DMA address structure.
  • len — The length, in bytes, of the data for this DMA transaction.
• Returns:
  • EOK — Success.
  • errno — An error occurred.

int bcm2711_dma_freebuf(void *const hdl, dma_addr_t *addr)

• Implements the dma_freebuf() function in the spi_funcs_t structure.
• Frees a DMA buffer.
• Arguments:
  • hdl — The handle of the low-level module returned by spi_init().
  • addr — A pointer to the DMA address structure.
• Returns:
  • EOK — Success.
  • errno — An error occurred.

Refer to the following SPI client samples:

• Generic SPI client API, implemented as static library (rpi_spi) — Provides the underlying logic to communicate with the SPI driver.
• WS 281x LED static library (librpi_ws281x) — Provides a generic API to write colors to a collection of WS 281x LEDs. This sample is suitable for simpler control of one or more LED strips, or one or more LED matrices, but doesn't contain specialized logic for managing matrices in a transparent fashion. It's a smaller port of the Linux library of the same name (https://github.com/jgarff/rpi_ws281x), but focuses only on the SPI driver of the original library. The implementation of this sample's SPI logic is based on the rpi_spi sample above.
• LED Strip Matrix application (rpi-ws281x-rainbow) — A sample application that demonstrates how to use the librpi_ws281x APIs to display a rainbow.

Given the hardware configuration, you can configure the device using the rpi_spi_configure_device() function from the SPI interface:

rpi_spi_configure_device(bus_number, device_number, 0b00010000010000100000, 6500000)

For the full initialization implementation for WS281x, refer to the ws2811_init() and spi_init() functions. The following diagram shows how the spi-bcm2711 driver communicates with an LED strip matrix:

After configuring the device, transfer data through SPI communication using the rpi_spi_write_read_data() function:

rpi_spi_write_read_data(bus_number, device_number, data, data_size)