/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ // Example of writing via DMA to the SPI interface and similarly reading it back via a loopback. #include <stdio.h> #include <stdlib.h> #include "pico/stdlib.h" #include "pico/binary_info.h" #include "hardware/spi.h" #include "hardware/dma.h" #define TEST_SIZE 1024 int main() { // Enable UART so we can print status output stdio_init_all(); #if !defined(spi_default) || !defined(PICO_DEFAULT_SPI_SCK_PIN) || !defined(PICO_DEFAULT_SPI_TX_PIN) || !defined(PICO_DEFAULT_SPI_RX_PIN) || !defined(PICO_DEFAULT_SPI_CSN_PIN) #warning spi/spi_dma example requires a board with SPI pins puts("Default SPI pins were not defined"); #else printf("SPI DMA example\n"); // Enable SPI at 1 MHz and connect to GPIOs spi_init(spi_default, 1000 * 1000); gpio_set_function(PICO_DEFAULT_SPI_RX_PIN, GPIO_FUNC_SPI); gpio_init(PICO_DEFAULT_SPI_CSN_PIN); gpio_set_function(PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI); gpio_set_function(PICO_DEFAULT_SPI_TX_PIN, GPIO_FUNC_SPI); // Make the SPI pins available to picotool bi_decl(bi_3pins_with_func(PICO_DEFAULT_SPI_RX_PIN, PICO_DEFAULT_SPI_TX_PIN, PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI)); // Make the CS pin available to picotool bi_decl(bi_1pin_with_name(PICO_DEFAULT_SPI_CSN_PIN, "SPI CS")); // Grab some unused dma channels const uint dma_tx = dma_claim_unused_channel(true); const uint dma_rx = dma_claim_unused_channel(true); // Force loopback for testing (I don't have an SPI device handy) hw_set_bits(&spi_get_hw(spi_default)->cr1, SPI_SSPCR1_LBM_BITS); static uint8_t txbuf[TEST_SIZE]; static uint8_t rxbuf[TEST_SIZE]; for (uint i = 0; i < TEST_SIZE; ++i) { txbuf[i] = rand(); } // We set the outbound DMA to transfer from a memory buffer to the SPI transmit FIFO paced by the SPI TX FIFO DREQ // The default is for the read address to increment every element (in this case 1 byte = DMA_SIZE_8) // and for the write address to remain unchanged. printf("Configure TX DMA\n"); dma_channel_config c = dma_channel_get_default_config(dma_tx); channel_config_set_transfer_data_size(&c, DMA_SIZE_8); channel_config_set_dreq(&c, spi_get_dreq(spi_default, true)); dma_channel_configure(dma_tx, &c, &spi_get_hw(spi_default)->dr, // write address txbuf, // read address TEST_SIZE, // element count (each element is of size transfer_data_size) false); // don't start yet printf("Configure RX DMA\n"); // We set the inbound DMA to transfer from the SPI receive FIFO to a memory buffer paced by the SPI RX FIFO DREQ // We configure the read address to remain unchanged for each element, but the write // address to increment (so data is written throughout the buffer) c = dma_channel_get_default_config(dma_rx); channel_config_set_transfer_data_size(&c, DMA_SIZE_8); channel_config_set_dreq(&c, spi_get_dreq(spi_default, false)); channel_config_set_read_increment(&c, false); channel_config_set_write_increment(&c, true); dma_channel_configure(dma_rx, &c, rxbuf, // write address &spi_get_hw(spi_default)->dr, // read address TEST_SIZE, // element count (each element is of size transfer_data_size) false); // don't start yet printf("Starting DMAs...\n"); // start them exactly simultaneously to avoid races (in extreme cases the FIFO could overflow) dma_start_channel_mask((1u << dma_tx) | (1u << dma_rx)); printf("Wait for RX complete...\n"); dma_channel_wait_for_finish_blocking(dma_rx); if (dma_channel_is_busy(dma_tx)) { panic("RX completed before TX"); } printf("Done. Checking..."); for (uint i = 0; i < TEST_SIZE; ++i) { if (rxbuf[i] != txbuf[i]) { panic("Mismatch at %d/%d: expected %02x, got %02x", i, TEST_SIZE, txbuf[i], rxbuf[i] ); } } printf("All good\n"); dma_channel_unclaim(dma_tx); dma_channel_unclaim(dma_rx); return 0; #endif }

This firmware image was imported from the pico-examples repository. 


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