SPI — 半双工 DMA (JTAG 引脚)

固件库: AT32F403A_407_Firmware_Library V2.2.2
芯片: AT32
源文件: AT32/AT32F403A_407_Firmware_Library_V2.2.2/project/at_start_f403a/examples/spi/halfduplex_dma_jtagpin/src/main.c

功能简介

本示例演示 SPI 半双工通信。同一时刻只能收或发，但只需要一根数据线（MOSI/MISO 复用）。

硬件准备

需要主机和从机两块板子，或使用回环连接（MOSI→MISO）

完整代码

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#include "at32f403a_407_board.h"
#include "at32f403a_407_clock.h"
#define SPI_MASTER_CS_HIGH   gpio_bits_set(GPIOA, GPIO_PINS_15)
#define SPI_MASTER_CS_LOW    gpio_bits_reset(GPIOA, GPIO_PINS_15)
#define BUFFER_SIZE          32

static void dma_config(void)
{
  dma_init_type dma_init_struct;
  crm_periph_clock_enable(CRM_DMA1_PERIPH_CLOCK, TRUE);
  
  /* use dma1_channel4 as spi2 receive channel */
  dma_reset(DMA1_CHANNEL4);
  dma_default_para_init(&dma_init_struct);
  dma_init_struct.buffer_size = BUFFER_SIZE;
  dma_init_struct.direction = DMA_DIR_PERIPHERAL_TO_MEMORY;
  dma_init_struct.memory_base_addr = (uint32_t)spi2_rx_buffer;
  dma_init_struct.memory_data_width = DMA_MEMORY_DATA_WIDTH_BYTE;
  dma_init_struct.memory_inc_enable = TRUE;
  dma_init_struct.peripheral_base_addr = (uint32_t)&(SPI2->dt);
  dma_init_struct.peripheral_data_width = DMA_PERIPHERAL_DATA_WIDTH_BYTE;
  dma_init_struct.peripheral_inc_enable = FALSE;
  dma_init_struct.priority = DMA_PRIORITY_MEDIUM;
  dma_init_struct.loop_mode_enable = FALSE;
  dma_init(DMA1_CHANNEL4, &dma_init_struct);
  
  crm_periph_clock_enable(CRM_DMA2_PERIPH_CLOCK, TRUE);
  
  /* use dma2_channel2 as spi3 transmit channel */
  dma_reset(DMA2_CHANNEL2);
  dma_default_para_init(&dma_init_struct);
  dma_init_struct.buffer_size = BUFFER_SIZE;
  dma_init_struct.direction = DMA_DIR_MEMORY_TO_PERIPHERAL;
  dma_init_struct.memory_base_addr = (uint32_t)spi3_tx_buffer;
  dma_init_struct.memory_data_width = DMA_MEMORY_DATA_WIDTH_BYTE;
  dma_init_struct.memory_inc_enable = TRUE;
  dma_init_struct.peripheral_base_addr = (uint32_t)&(SPI3->dt);
  dma_init_struct.peripheral_data_width = DMA_PERIPHERAL_DATA_WIDTH_BYTE;
  dma_init_struct.peripheral_inc_enable = FALSE;
  dma_init_struct.priority = DMA_PRIORITY_MEDIUM;
  dma_init_struct.loop_mode_enable = FALSE;
  dma_init(DMA2_CHANNEL2, &dma_init_struct);
}

static void spi_config(void)
{
  spi_init_type spi_init_struct;
  
  /* spi master initialization */
  crm_periph_clock_enable(CRM_SPI3_PERIPH_CLOCK, TRUE);
  spi_default_para_init(&spi_init_struct);
  
  /* single line bidirectional half duplex mode-transmitting */
  spi_init_struct.transmission_mode = SPI_TRANSMIT_HALF_DUPLEX_TX;
  spi_init_struct.master_slave_mode = SPI_MODE_MASTER;
  spi_init_struct.mclk_freq_division = SPI_MCLK_DIV_8;
  spi_init_struct.first_bit_transmission = SPI_FIRST_BIT_MSB;
  spi_init_struct.frame_bit_num = SPI_FRAME_8BIT;
  spi_init_struct.clock_polarity = SPI_CLOCK_POLARITY_LOW;
  spi_init_struct.clock_phase = SPI_CLOCK_PHASE_2EDGE;
  spi_init_struct.cs_mode_selection = SPI_CS_SOFTWARE_MODE;
  spi_init(SPI3, &spi_init_struct);
  
  /* use dma transmit */
  spi_i2s_dma_transmitter_enable(SPI3, TRUE);
  
  spi_enable(SPI3, TRUE);
  
  /* spi slave initialization */
  crm_periph_clock_enable(CRM_SPI2_PERIPH_CLOCK, TRUE);
  
  /* single line bidirectional half duplex mode-receiving */
  spi_init_struct.transmission_mode = SPI_TRANSMIT_HALF_DUPLEX_RX;
  spi_init_struct.master_slave_mode = SPI_MODE_SLAVE;
  spi_init_struct.mclk_freq_division = SPI_MCLK_DIV_8;
  spi_init_struct.first_bit_transmission = SPI_FIRST_BIT_MSB;
  spi_init_struct.frame_bit_num = SPI_FRAME_8BIT;
  spi_init_struct.clock_polarity = SPI_CLOCK_POLARITY_LOW;
  spi_init_struct.clock_phase = SPI_CLOCK_PHASE_2EDGE;
  spi_init_struct.cs_mode_selection = SPI_CS_HARDWARE_MODE;
  spi_init(SPI2, &spi_init_struct);
  
  /* use dma receive */
  spi_i2s_dma_receiver_enable(SPI2, TRUE);
  
  spi_enable(SPI2, TRUE);
}

static void gpio_config(void)
{
  gpio_init_type gpio_initstructure;
  crm_periph_clock_enable(CRM_GPIOA_PERIPH_CLOCK, TRUE);
  crm_periph_clock_enable(CRM_GPIOB_PERIPH_CLOCK, TRUE);
  crm_periph_clock_enable(CRM_IOMUX_PERIPH_CLOCK, TRUE);
  gpio_pin_remap_config(SWJTAG_GMUX_010, TRUE);
  gpio_pin_remap_config(SPI3_GMUX_0010, TRUE);
  
  /* master cs pin */
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_OUTPUT;
  gpio_initstructure.gpio_pins = GPIO_PINS_15;
  gpio_init(GPIOA, &gpio_initstructure);
  
  /* non communication time: master pull up CS pin release slave */
  SPI_MASTER_CS_HIGH;
  
  /* master sck pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_DOWN;
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_3;
  gpio_init(GPIOB, &gpio_initstructure);

  /* master mosi pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_5;
  gpio_init(GPIOB, &gpio_initstructure);
  
  /* slave cs pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  gpio_initstructure.gpio_pins = GPIO_PINS_12;
  gpio_init(GPIOB, &gpio_initstructure);
  
  /* slave sck pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_DOWN;
  gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  gpio_initstructure.gpio_pins = GPIO_PINS_13;
  gpio_init(GPIOB, &gpio_initstructure);

  /* slave miso pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_14;
  gpio_init(GPIOB, &gpio_initstructure);
}

int main(void)
{
  system_clock_config();
  at32_board_init();
  at32_led_on(LED4);
  
  gpio_config();
  dma_config();
  spi_config();
  
  /* start communication: master pull down CS pin select slave */
  SPI_MASTER_CS_LOW;
  
  /* enable spi slave dma to get data */
  dma_channel_enable(DMA1_CHANNEL4, TRUE);
  
  /* enable spi master dma to fill data */
  dma_channel_enable(DMA2_CHANNEL2, TRUE);
  
  /* wait master spi data fill end */
  while(dma_flag_get(DMA2_FDT2_FLAG) == RESET)
  {
  }
  
  /* wait slave spi data get end */
  while(dma_flag_get(DMA1_FDT4_FLAG) == RESET)
  {
  }
  
  /* wait master and slave idle when communication end */
  while(spi_i2s_flag_get(SPI3, SPI_I2S_BF_FLAG) != RESET);
  while(spi_i2s_flag_get(SPI2, SPI_I2S_BF_FLAG) != RESET);
  
  /* end communication: master pull up CS pin release slave */
  SPI_MASTER_CS_HIGH;

  /* test result:the data check */
  transfer_status = buffer_compare(spi2_rx_buffer, spi3_tx_buffer, BUFFER_SIZE);

  /* test result indicate:if SUCCESS ,led2 lights */
  if(transfer_status == SUCCESS)
  {
    at32_led_on(LED2);
  }
  else
  {
    at32_led_on(LED3);
  }
  while(1)
  {
  }
}

代码讲解

系统时钟初始化：配置 MCU 的主频和时钟树。不同芯片的时钟配置不同，一般由工具生成。

板级初始化：初始化开发板上的 LED、按键等基础外设。

GPIO 配置：设置引脚为输出/输入模式，选择推挽/开漏输出，配置上拉/下拉。

DMA 配置：设置源地址、目标地址、传输方向、数据宽度。DMA 搬运数据不占用 CPU。

SPI 配置：设置主/从模式、时钟极性（CPOL）、时钟相位（CPHA）、分频系数。主机和从机的 CPOL/CPHA 必须一致。

实验现象

主机和从机互相交换数据
数据校验通过则 LED 指示成功

注意事项

CPOL 和 CPHA 必须主机从机一致
片选（CS）信号要手动拉低选中从机
时钟频率不能超过从设备的最大速率

AT32 SPI — 半双工 DMA (JTAG 引脚)

AT32 AT32F403A_407_Firmware_Library V2.2.2 SPI 半双工 DMA (JTAG 引脚) 示例教学