pio_spi.c (spi sample)

/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include "pio_spi.h" // Just 8 bit functions provided here. The PIO program supports any frame size // 1...32, but the software to do the necessary FIFO shuffling is left as an // exercise for the reader :) // // Likewise we only provide MSB-first here. To do LSB-first, you need to // - Do shifts when reading from the FIFO, for general case n != 8, 16, 32 // - Do a narrow read at a one halfword or 3 byte offset for n == 16, 8 // in order to get the read data correctly justified. void __time_critical_func(pio_spi_write8_blocking)(const pio_spi_inst_t *spi, const uint8_t *src, size_t len) { size_t tx_remain = len, rx_remain = len; // Do 8 bit accesses on FIFO, so that write data is byte-replicated. This // gets us the left-justification for free (for MSB-first shift-out) io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm]; io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm]; while (tx_remain || rx_remain) { if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) { *txfifo = *src++; --tx_remain; } if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) { (void) *rxfifo; --rx_remain; } } } void __time_critical_func(pio_spi_read8_blocking)(const pio_spi_inst_t *spi, uint8_t *dst, size_t len) { size_t tx_remain = len, rx_remain = len; io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm]; io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm]; while (tx_remain || rx_remain) { if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) { *txfifo = 0; --tx_remain; } if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) { *dst++ = *rxfifo; --rx_remain; } } } void __time_critical_func(pio_spi_write8_read8_blocking)(const pio_spi_inst_t *spi, uint8_t *src, uint8_t *dst, size_t len) { size_t tx_remain = len, rx_remain = len; io_rw_8 *txfifo = (io_rw_8 *) &spi->pio->txf[spi->sm]; io_rw_8 *rxfifo = (io_rw_8 *) &spi->pio->rxf[spi->sm]; while (tx_remain || rx_remain) { if (tx_remain && !pio_sm_is_tx_fifo_full(spi->pio, spi->sm)) { *txfifo = *src++; --tx_remain; } if (rx_remain && !pio_sm_is_rx_fifo_empty(spi->pio, spi->sm)) { *dst++ = *rxfifo; --rx_remain; } } }