SPI — 全双工轮询通信

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/fullduplex_polling/src/main.c

功能简介

本示例演示 SPI 全双工通信。主机和从机可以同时收发数据，速度比 I2C 快得多。适合高速数据传输场景。

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"
#include <stdio.h>
#define SPI1_AS_MASTER_CS_HIGH   gpio_bits_set(GPIOA, GPIO_PINS_4)
#define SPI1_AS_MASTER_CS_LOW    gpio_bits_reset(GPIOA, GPIO_PINS_4)
#define SPI2_AS_MASTER_CS_HIGH   gpio_bits_set(GPIOB, GPIO_PINS_12)
#define SPI2_AS_MASTER_CS_LOW    gpio_bits_reset(GPIOB, GPIO_PINS_12)
#define BUFFER_SIZE              32

static void spi_config(void)
{
  /* master spi initialization */
  crm_periph_clock_enable(CRM_SPI1_PERIPH_CLOCK, TRUE);
  spi_default_para_init(&spi_init_struct);
  
  /* dual line unidirectional full-duplex mode */
  spi_init_struct.transmission_mode = SPI_TRANSMIT_FULL_DUPLEX;
  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_LSB;
  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(SPI1, &spi_init_struct);
  
  spi_enable(SPI1, TRUE);
  
  /* slave spi initialization */
  crm_periph_clock_enable(CRM_SPI2_PERIPH_CLOCK, TRUE);
  
  /* dual line unidirectional full-duplex mode */
  spi_init_struct.transmission_mode = SPI_TRANSMIT_FULL_DUPLEX;
  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_LSB;
  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);

  spi_enable(SPI2, TRUE);
}

static void gpio_config(uint16_t spi1_mode, uint16_t spi2_mode)
{
  gpio_init_type gpio_initstructure;
  crm_periph_clock_enable(CRM_GPIOA_PERIPH_CLOCK, TRUE);
  crm_periph_clock_enable(CRM_GPIOB_PERIPH_CLOCK, TRUE);
  gpio_default_para_init(&gpio_initstructure);
  
  /* spi1 cs pin */
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  if(spi1_mode == SPI_MODE_MASTER)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_OUTPUT;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_4;
  gpio_init(GPIOA, &gpio_initstructure);
  
  /* spi1 sck pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_DOWN;
  if(spi1_mode == SPI_MODE_MASTER)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_5;
  gpio_init(GPIOA, &gpio_initstructure);

  /* spi1 miso pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  if(spi1_mode == SPI_MODE_MASTER)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_6;
  gpio_init(GPIOA, &gpio_initstructure);

  /* spi1 mosi pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  if(spi1_mode == SPI_MODE_MASTER)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_7;
  gpio_init(GPIOA, &gpio_initstructure);
  
  /* spi2 cs pin */
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  if(spi2_mode == SPI_MODE_SLAVE)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_OUTPUT;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_12;
  gpio_init(GPIOB, &gpio_initstructure);

  /* spi2 sck pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_DOWN;
  if(spi2_mode == SPI_MODE_SLAVE)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_13;
  gpio_init(GPIOB, &gpio_initstructure);

  /* spi2 miso pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  if(spi2_mode == SPI_MODE_SLAVE)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_14;
  gpio_init(GPIOB, &gpio_initstructure);

  /* spi2 mosi pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  if(spi2_mode == SPI_MODE_SLAVE)
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  }
  else
  {
    gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  }
  gpio_initstructure.gpio_pins = GPIO_PINS_15;
  gpio_init(GPIOB, &gpio_initstructure);
  
  /* non communication time: master pull up CS pin release slave */
  if(spi1_mode == SPI_MODE_MASTER)
  {
    SPI1_AS_MASTER_CS_HIGH;
  }
  if(spi2_mode == SPI_MODE_MASTER)
  {
    SPI2_AS_MASTER_CS_HIGH;
  }
}

int main(void)
{
  __IO uint32_t index = 0;
  system_clock_config();
  at32_board_init();
  at32_led_on(LED4);
  gpio_config(SPI_MODE_MASTER, SPI_MODE_SLAVE);
  spi_config();
  
  /* start communication: master pull down CS pin select slave */
  SPI1_AS_MASTER_CS_LOW;
  
  /* transfer procedure:the "BUFFER_SIZE" data transfer */
  while(tx_index < BUFFER_SIZE)
  {
    /* slave and master transmit data fill */
    while(spi_i2s_flag_get(SPI2, SPI_I2S_TDBE_FLAG) == RESET);
    spi_i2s_data_transmit(SPI2, spi2_tx_buffer[tx_index]);
    while(spi_i2s_flag_get(SPI1, SPI_I2S_TDBE_FLAG) == RESET);
    spi_i2s_data_transmit(SPI1, spi1_tx_buffer[tx_index++]);
    
    /* slave and master receive data get */
    while(spi_i2s_flag_get(SPI2, SPI_I2S_RDBF_FLAG) == RESET);
    spi2_rx_buffer[rx_index] = spi_i2s_data_receive(SPI2);
    while(spi_i2s_flag_get(SPI1, SPI_I2S_RDBF_FLAG) == RESET);
    spi1_rx_buffer[rx_index++] = spi_i2s_data_receive(SPI1);
  }
  
  /* wait master and slave idle when communication end */
  while(spi_i2s_flag_get(SPI1, 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 */
  SPI1_AS_MASTER_CS_HIGH;
  
  /* test result:the data check */
  transfer_status1 = buffer_compare(spi2_rx_buffer, spi1_tx_buffer, BUFFER_SIZE);
  transfer_status2 = buffer_compare(spi1_rx_buffer, spi2_tx_buffer, BUFFER_SIZE);
  
  spi_enable(SPI1, FALSE);
  spi_enable(SPI2, FALSE);
  
  /* master & slave mode switch */
  gpio_config(SPI_MODE_SLAVE, SPI_MODE_MASTER);
  spi_init_struct.master_slave_mode =SPI_MODE_SLAVE;
  spi_init_struct.cs_mode_selection = SPI_CS_HARDWARE_MODE;
  spi_init(SPI1, &spi_init_struct);
  
  spi_init_struct.master_slave_mode =SPI_MODE_MASTER;
  spi_init_struct.cs_mode_selection = SPI_CS_SOFTWARE_MODE;
  spi_init(SPI2, &spi_init_struct);
  
  /* receive buffer clear */
  tx_index = 0;
  rx_index = 0;
  for(index = 0; index < BUFFER_SIZE; index++)
  {
    spi1_rx_buffer[index] = 0;
    spi2_rx_buffer[index] = 0;
  }
  
  spi_enable(SPI2, TRUE);
  spi_enable(SPI1, TRUE);
  
  /* start communication: master pull down CS pin select slave */
  SPI2_AS_MASTER_CS_LOW;

  /* transfer procedure:the "BUFFER_SIZE" data transfer */
  while(tx_index < BUFFER_SIZE)
  {
    /* slave and master transmit data fill */
    while(spi_i2s_flag_get(SPI1, SPI_I2S_TDBE_FLAG) == RESET);
    spi_i2s_data_transmit(SPI1, spi1_tx_buffer[tx_index]);
    while(spi_i2s_flag_get(SPI2, SPI_I2S_TDBE_FLAG) == RESET);
    spi_i2s_data_transmit(SPI2, spi2_tx_buffer[tx_index++]);
    
    /* slave and master receive data get */
    while(spi_i2s_flag_get(SPI1, SPI_I2S_RDBF_FLAG) == RESET);
    spi1_rx_buffer[rx_index] = spi_i2s_data_receive(SPI1);
    while(spi_i2s_flag_get(SPI2, SPI_I2S_RDBF_FLAG) == RESET);
    spi2_rx_buffer[rx_index++] = spi_i2s_data_receive(SPI2);
  }
  
  /* wait master and slave idle when communication end */
  while(spi_i2s_flag_get(SPI2, SPI_I2S_BF_FLAG) != RESET);
  while(spi_i2s_flag_get(SPI1, SPI_I2S_BF_FLAG) != RESET);
  
  /* end communication: master pull up CS pin release slave */
  SPI2_AS_MASTER_CS_HIGH;

  /* test result:the data check */
  transfer_status3 = buffer_compare(spi2_rx_buffer, spi1_tx_buffer, BUFFER_SIZE);
  transfer_status4 = buffer_compare(spi1_rx_buffer, spi2_tx_buffer, BUFFER_SIZE);

  /* test result indicate:if SUCCESS ,led2 lights */
  if((transfer_status1 == SUCCESS) && (transfer_status2 == SUCCESS) && \
     (transfer_status3 == SUCCESS) && (transfer_status4 == 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。

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 — 全双工轮询通信

AT32 AT32F403A_407_Firmware_Library V2.2.2 SPI 全双工轮询通信示例教学