文章目录
本篇是对GD32的I2C外设应用，温湿度芯片是htu21d，gd32芯片是gd32f350k8u6，基于gd32的标准外设库进行开发。
一、温湿度传感器htu21d介绍
1.1 参数
只列举芯片温湿度测量的精度，功耗、时序等参数请参考手册。
1.1.1 湿度参数
1.1.2 温度参数
1.2 芯片i2c协议
1.2.1 器件地址
器件的7位地址为0x40，编程的时候需加上读写方向位，为0x80。
1.2.2 读取温湿度
1.2.3 芯片复位
二、gd32的i2c外设介绍
I2C接口是一种内部电路，允许与外部I2C接口进行通信，外部I2C接口是一种工业标准的两线串行接口，用于连接外部硬件。这两条串行线被称为串行数据线（SDA）和串行时钟线（SCL）。I2C模块提供不同的数据传输速率：标准模式高达100 KHz，快速模式高达400 KHz，快速模式plus高达1 MHz。I2C模块还具有仲裁检测功能，以防止多个主机同时尝试向I2C总线传输数据的情况。在I2C接口中还提供了一个CRC-8计算器，用于对I2C数据进行包错误检查。
- 最多两个I2C总线接口可支持主从模式，频率高达1 MHz（快速模式增强）
- 提供仲裁功能，可选PEC（包错误检查）生成和检查
- 支持7位和10位寻址模式以及通用呼叫寻址模式
三、编程
3.1 宏定义和变量
#define HTU21D_ADDR 0x80
#define HTU21D_TEMP 0xf3
#define HTU21D_HUMI 0Xf5
#define HTU21D_SOFTWARE_RESET 0xfe
3.2 gd32初始化i2c外设和htu21d初始化
3.2.1 gd32 i2c初始化
//IO引脚配置
void gpio_config(void)
{
/* enable GPIOB clock */
rcu_periph_clock_enable(RCU_GPIOB);
/* enable I2C0 clock */
rcu_periph_clock_enable(RCU_I2C0);
/* connect PB6 to I2C0_SCL */
gpio_af_set(GPIOB, GPIO_AF_1, GPIO_PIN_6);
/* connect PB7 to I2C0_SDA */
gpio_af_set(GPIOB, GPIO_AF_1, GPIO_PIN_7);
/* configure GPIO pins of I2C0 */
gpio_mode_set(GPIOB, GPIO_MODE_AF, GPIO_PUPD_PULLUP,GPIO_PIN_6);
gpio_output_options_set(GPIOB, GPIO_OTYPE_OD, GPIO_OSPEED_50MHZ,GPIO_PIN_6);
gpio_mode_set(GPIOB, GPIO_MODE_AF, GPIO_PUPD_PULLUP,GPIO_PIN_7);
gpio_output_options_set(GPIOB, GPIO_OTYPE_OD, GPIO_OSPEED_50MHZ,GPIO_PIN_7);
}
//I2C外设配置
void i2c_config(void)
{
/* enable I2C clock */
rcu_periph_clock_enable(RCU_I2C0);
/* configure I2C clock */
i2c_clock_config(I2C0,I2C0_SPEED,I2C_DTCY_2);
/* configure I2C address */
i2c_mode_addr_config(I2C0,I2C_I2CMODE_ENABLE,I2C_ADDFORMAT_7BITS,HTU21D_ADDR);
/* enable I2C0 */
i2c_enable(I2C0);
/* enable acknowledge */
i2c_ack_config(I2C0,I2C_ACK_ENABLE);
}
3.2.2 htu21d初始化
void htu21d_init(void)
{
/* wait until I2C bus is idle */
while(i2c_flag_get(I2C0, I2C_FLAG_I2CBSY));
i2c_start_on_bus(I2C0);
/* wait until SBSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_SBSEND)){
};
/* send slave address to I2C bus */
i2c_master_addressing(I2C0, HTU21D_ADDR, I2C_TRANSMITTER);
/* wait until ADDSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_ADDSEND)){
};
/* clear the ADDSEND bit */
i2c_flag_clear(I2C0,I2C_FLAG_ADDSEND);
/* wait until the transmit data buffer is empty */
while( SET != i2c_flag_get(I2C0, I2C_FLAG_TBE)){
};
i2c_data_transmit(I2C0, HTU21D_SOFTWARE_RESET);
/* wait until BTC bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_BTC)){
};
i2c_stop_on_bus(I2C0);
/* wait until the stop condition is finished */
while(I2C_CTL0(I2C0)&0x0200){
};
delay_1ms(15);
}
3.2 温湿度测量
float htu21d_measure(uint8_t _ucOrder)
{
uint8_t ucMsb,ucLsb,checksum;//checksum校验和没有用上
volatile float f_Temp,f_Humi,f_RetVal;
i2c_ackpos_config(I2C0, I2C_ACKPOS_CURRENT);
/* wait until I2C bus is idle */
while(i2c_flag_get(I2C0, I2C_FLAG_I2CBSY)){
};
i2c_start_on_bus(I2C0);
/* wait until SBSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_SBSEND)){
};
i2c_master_addressing(I2C0, HTU21D_ADDR, I2C_TRANSMITTER);
/* wait until ADDSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_ADDSEND)){
};
/* clear the ADDSEND bit */
i2c_flag_clear(I2C0,I2C_FLAG_ADDSEND);
/* wait until the transmit data buffer is empty */
while( SET != i2c_flag_get(I2C0, I2C_FLAG_TBE)){
};
i2c_data_transmit(I2C0, _ucOrder);
/* wait until BTC bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_BTC)){
};
/* send a stop condition to I2C bus */
delay_1ms(80);
i2c_start_on_bus(I2C0);
/* wait until SBSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_SBSEND)){
};
/* send slave address to I2C bus */
i2c_master_addressing(I2C0, HTU21D_ADDR, I2C_RECEIVER);
/* wait until ADDSEND bit is set */
while(!i2c_flag_get(I2C0, I2C_FLAG_ADDSEND)){
};
/* clear the ADDSEND bit */
i2c_flag_clear(I2C0,I2C_FLAG_ADDSEND);
/* send a stop condition to I2C bus */
delay_1ms(5);
if(i2c_flag_get(I2C0, I2C_FLAG_RBNE)){
ucMsb = i2c_data_receive(I2C0);
}
if(i2c_flag_get(I2C0, I2C_FLAG_RBNE)){
ucLsb = i2c_data_receive(I2C0);
}
i2c_ack_config(I2C0, I2C_ACK_DISABLE);
if(i2c_flag_get(I2C0, I2C_FLAG_RBNE)){
checksum = i2c_data_receive(I2C0);
}
i2c_stop_on_bus(I2C0);
/* wait until the stop condition is finished */
while(I2C_CTL0(I2C0)&0x0200);
/* enable acknowledge */
i2c_ack_config(I2C0, I2C_ACK_ENABLE);
i2c_ackpos_config(I2C0, I2C_ACKPOS_CURRENT);
ucLsb &= 0xfc; //设置分辨率,最低两位为0,温度:14位;湿度:12位
f_RetVal = ucMsb * 256 + ucLsb;/*MSB=(MSB<<=8)+LSB;即将MSB移位到高8位*/
if(_ucOrder == HTU21D_TEMP)
{
f_Temp = (175.72)*f_RetVal/65536-46.85;//温度:T= -46.85 + 175.72 * ST/2^16
return f_Temp;
}
else if(_ucOrder == HTU21D_HUMI)
{
f_Humi = (f_RetVal*125)/65536-6;//湿度: RH%= -6 + 125 * SRH/2^16
return f_Humi;
}
else
return 0;
}
3.3 测试程序
htu21d_init();
f_RetVal = htu21d_measure(HTU21D_TEMP);//得到温度值
printf("The htu measure temp is :%4.2fC ",f_RetVal);
printf("");
htu21d_init();
f_RetVal= htu21d_measure(HTU21D_HUMI); //得到湿度值
printf("The htu measure humi is :%4.2fRH \r\n",f_RetVal);
四、测试
烧录程序后，打印出测量得到的温湿度数据正常。
