AT32 SPI

AT32 SPI — 半双工收发切换

AT32 AT32F403A_407_Firmware_Library V2.2.2 SPI 半双工收发切换 示例教学

SPI — 半双工收发切换

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_transceiver_switch/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 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183

#include "at32f403a_407_board.h"
#include "at32f403a_407_clock.h"
#define SPI_MASTER_CS_HIGH   gpio_bits_set(GPIOA, GPIO_PINS_4)
#define SPI_MASTER_CS_LOW    gpio_bits_reset(GPIOA, GPIO_PINS_4)
#define BUFFER_SIZE          32

static void spi_config(void)
{
  /* master spi initialization */
  crm_periph_clock_enable(CRM_SPI1_PERIPH_CLOCK, TRUE);
  nvic_irq_enable(SPI1_IRQn, 0, 0);
  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_256;
  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(SPI1, &spi_init_struct);
  
  /* enable transmit data buffer empty interrupt */
  spi_i2s_interrupt_enable(SPI1, SPI_I2S_TDBE_INT, TRUE);
  
  /* slave spi initialization */
  crm_periph_clock_enable(CRM_SPI2_PERIPH_CLOCK, TRUE);
  nvic_irq_enable(SPI2_I2S2EXT_IRQn, 0, 0);
  
  /* 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_256;
  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);

  /* enable receive data buffer full interrupt */
  spi_i2s_interrupt_enable(SPI2, SPI_I2S_RDBF_INT, 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);
  gpio_default_para_init(&gpio_initstructure);
  
  /* master spi cs pin */
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_OUTPUT;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  gpio_initstructure.gpio_pins = GPIO_PINS_4;
  gpio_init(GPIOA, &gpio_initstructure);
  
  /* non communication time: master pull up CS pin release slave */
  SPI_MASTER_CS_HIGH;

  /* master spi sck 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_DOWN;
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_5;
  gpio_init(GPIOA, &gpio_initstructure);

  /* master spi mosi pin */
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_MUX;
  gpio_initstructure.gpio_pins = GPIO_PINS_7;
  gpio_init(GPIOA, &gpio_initstructure);
  
  /* slave spi cs pin */
  gpio_initstructure.gpio_out_type = GPIO_OUTPUT_PUSH_PULL;
  gpio_initstructure.gpio_pull = GPIO_PULL_UP;
  gpio_initstructure.gpio_mode = GPIO_MODE_INPUT;
  gpio_initstructure.gpio_drive_strength = GPIO_DRIVE_STRENGTH_STRONGER;
  gpio_initstructure.gpio_pins = GPIO_PINS_12;
  gpio_init(GPIOB, &gpio_initstructure);

  /* slave spi 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 spi 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);
  nvic_priority_group_config(NVIC_PRIORITY_GROUP_4);
  gpio_config();
  
  /* config spi1 send spi2 receive */
  spi_config();
  
  /* start communication: master pull down CS pin select slave */
  SPI_MASTER_CS_LOW;
  
  spi_enable(SPI2, TRUE);
  spi_enable(SPI1, TRUE);
  
  /* wait data receive end */
  while(rx_index < BUFFER_SIZE);
  
  /* 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 */
  SPI_MASTER_CS_HIGH;
  
  /* test result:the data check */
  transfer_status1 = buffer_compare(spi2_rx_buffer, spi1_tx_buffer, BUFFER_SIZE);
  
  /* config spi2 send spi1 receive */
  spi_enable(SPI1, FALSE);
  spi_enable(SPI2, FALSE);
    
  rx_index = 0;
  tx_index = 0;
  spi_i2s_interrupt_enable(SPI1, SPI_I2S_TDBE_INT, FALSE);
  spi_i2s_interrupt_enable(SPI2, SPI_I2S_RDBF_INT, FALSE);
  
  /* 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_MASTER;
  spi_init_struct.cs_mode_selection = SPI_CS_SOFTWARE_MODE;
  spi_init(SPI1, &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_SLAVE;
  spi_init_struct.cs_mode_selection = SPI_CS_HARDWARE_MODE;
  spi_init(SPI2, &spi_init_struct);

  spi_i2s_interrupt_enable(SPI1, SPI_I2S_RDBF_INT, TRUE);
  spi_i2s_interrupt_enable(SPI2, SPI_I2S_TDBE_INT, TRUE);
  
  /* start communication: master pull down CS pin select slave */
  SPI_MASTER_CS_LOW;
  
  spi_enable(SPI2, TRUE);
  spi_enable(SPI1, TRUE);
  
  /* wait slave data receive end */
  while(rx_index < BUFFER_SIZE);
  
  /* master half duplex receiving modethe busy flag isnot usefull */
  
  /* end communication: master pull up CS pin release slave */
  SPI_MASTER_CS_HIGH;
  
  /* test result:the data check */
  transfer_status2 = buffer_compare(spi1_rx_buffer, spi2_tx_buffer, BUFFER_SIZE);

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

中断优先级配置：NVIC 设置中断的抢占优先级和子优先级。数字越小优先级越高。

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
© 2020 - 2026 CLing
世界是你们
使用 Hugo 构建
主题 Stack 由 Jimmy 设计