bcm_spi_transfer.c

uint8_t bcm_spi_transfer(uint8_t value)
{
    volatile uint32_t* paddr = bcm_spi0 + BCM_SPI0_CS/4;
    volatile uint32_t* fifo = bcm_spi0 + BCM_SPI0_FIFO/4;
    uint32_t ret;

    bcm_peri_set_bits(paddr, BCM_SPI0_CS_CLEAR, BCM_SPI0_CS_CLEAR);

    /* Set TA = 1, data transfer is active */
    bcm_peri_set_bits(paddr, BCM_SPI0_CS_TA, BCM_SPI0_CS_TA);

    /* Maybe wait for TXD (e.g., if it can't accept any data because the FIFO is full) */
    while (!(bcm_peri_read(paddr) & BCM_SPI0_CS_TXD))
        ;

    /* Write to FIFO, no barrier */
    bcm_peri_write_nb(fifo, bcm_correct_order(value));

    /* Wait for DONE to be set */
    while (!(bcm_peri_read_nb(paddr) & BCM_SPI0_CS_DONE))
        ;

    /* Read any byte that was sent back by the slave while we sere sending to it */
    ret = bcm_correct_order(bcm_peri_read_nb(fifo));

    /* Set TA = 0 (transfer is finished), and also set the barrier */
    bcm_peri_set_bits(paddr, 0, BCM_SPI0_CS_TA);

    return ret;
}