【上海晶珩睿莓1开发板试用体验】6、I2C通信-读取BME280温湿度气压数据

https://github.com/libdriver/bme280

bme280

BME280简介

BME280连接睿莓1

将BME280模块的SDA接PIN3，SCL接PIN5，VCC接3V3，GND接GND

使用命令

i2cdetect -y 1

该命令查看在I2C1上挂载的设备，可以查询到BME280的地址:0x76

编写读取程序

我的程序是基于开源仓库修改、实现接口而来的。仓库地址:https://github.com/libdriver/bme280

编写bme280.c

#include <stdio.h>
#include <stdlib.h>
#include "driver_bme280.h"
#include "driver_bme280_interface.h"
#include "driver_bme280_basic.h"

int main()
{
    uint8_t res;
    float temperature_c;
    float pressure_pa;
    float humidity_percentage;

    res = bme280_basic_init(BME280_INTERFACE_IIC, BME280_ADDRESS_ADO_LOW);
    if (res != 0)
    {
        return 1;
    }

    while (1)
    {
        /* delay 1000ms */
        bme280_interface_delay_ms(1000);

        /* read data */
        res = bme280_basic_read((float *)&temperature_c, (float *)&pressure_pa, (float *)&humidity_percentage);
        if (res != 0)
        {
            (void)bme280_basic_deinit();
            return 1;
        }

        bme280_interface_debug_print("bme280: temperature is %0.2fC.\n", temperature_c);
        bme280_interface_debug_print("bme280: pressure is %0.2fPa.\n", pressure_pa);
        bme280_interface_debug_print("bme280: humidity is %0.2f%%.\n", humidity_percentage);
    }
    exit(0);
}

完善driver_bme280_interface_template.c

#include "driver_bme280_interface.h"

#include <stdio.h>
#include <stdint.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>

#include <linux/i2c-dev.h>
#include <linux/i2c.h>

#ifndef BME280_I2C_DEV
#define BME280_I2C_DEV "/dev/i2c-1"
#endif

static int s_i2c_fd = -1;

/* --------------- I2C 接口实现 --------------- */

uint8_t bme280_interface_iic_init(void)
{
    if (s_i2c_fd >= 0)
    {
        return 0;
    }

    s_i2c_fd = open(BME280_I2C_DEV, O_RDWR);
    if (s_i2c_fd < 0)
    {
        bme280_interface_debug_print("bme280 iic init: open %s failed: %s\n",
                                     BME280_I2C_DEV, strerror(errno));
        return 1;
    }
    return 0;
}

uint8_t bme280_interface_iic_deinit(void)
{
    if (s_i2c_fd >= 0)
    {
        if (close(s_i2c_fd) < 0)
        {
            bme280_interface_debug_print("bme280 iic deinit: close failed: %s\n",
                                         strerror(errno));
            s_i2c_fd = -1;
            return 1;
        }
        s_i2c_fd = -1;
    }
    return 0;
}

uint8_t bme280_interface_iic_read(uint8_t addr, uint8_t reg, uint8_t *buf, uint16_t len)
{
    if (s_i2c_fd < 0)
    {
        bme280_interface_debug_print("bme280 iic read: bus not init.\n");
        return 1;
    }
    if (buf == NULL || len == 0)
    {
        bme280_interface_debug_print("bme280 iic read: invalid param.\n");
        return 1;
    }

    addr >>= 1;

    /* 设置从设备地址 */
    if (ioctl(s_i2c_fd, I2C_SLAVE, addr) < 0)
    {
        bme280_interface_debug_print("bme280 iic read: set slave 0x%02X  failed: %s\n", addr, strerror(errno));
        return 1;
    }

    /* 组合消息：先写寄存器地址，再读数据 */
    struct i2c_rdwr_ioctl_data ioctl_data;
    struct i2c_msg msgs[2];
    uint8_t reg_buf = reg;

    msgs[0].addr = addr;
    msgs[0].flags = 0; /* 写 */
    msgs[0].len = 1;
    msgs[0].buf = &reg_buf;

    msgs[1].addr = addr;
    msgs[1].flags = I2C_M_RD; /* 读 */
    msgs[1].len = len;
    msgs[1].buf = buf;

    ioctl_data.msgs = msgs;
    ioctl_data.nmsgs = 2;

    if (ioctl(s_i2c_fd, I2C_RDWR, &ioctl_data) < 0)
    {
        bme280_interface_debug_print("bme280 iic read: ioctl I2C_RDWR failed: %s\n", strerror(errno));
        return 1;
    }

    return 0;
}

uint8_t bme280_interface_iic_write(uint8_t addr, uint8_t reg, uint8_t *buf, uint16_t len)
{
    if (s_i2c_fd < 0)
    {
        bme280_interface_debug_print("bme280 iic write: bus not init.\n");
        return 1;
    }
    if (len == 0)
    {
        bme280_interface_debug_print("bme280 iic write: length 0.\n");
        return 1;
    }

    /* 转换为 7-bit 地址 */
    uint8_t addr7 = addr >> 1;
    if (ioctl(s_i2c_fd, I2C_SLAVE, addr7) < 0)
    {
        bme280_interface_debug_print("bme280 iic write: set slave 0x%02X (from 0x%02X) failed: %s\n", addr7, addr, strerror(errno));
        return 1;
    }

    /* 发送寄存器地址 + 数据 */
    struct i2c_rdwr_ioctl_data ioctl_data;
    struct i2c_msg msg;
    uint8_t tx[len + 1];
    tx[0] = reg;
    memcpy(&tx[1], buf, len);

    msg.addr = addr7;
    msg.flags = 0; /* 写 */
    msg.len = len + 1;
    msg.buf = tx;

    ioctl_data.msgs = &msg;
    ioctl_data.nmsgs = 1;

    if (ioctl(s_i2c_fd, I2C_RDWR, &ioctl_data) < 0)
    {
        bme280_interface_debug_print("bme280 iic write: ioctl I2C_RDWR failed: %s\n", strerror(errno));
        return 1;
    }

    return 0;
}

/* --------------- SPI 接口（未实现） --------------- */

uint8_t bme280_interface_spi_init(void)
{
    return 1;
}

uint8_t bme280_interface_spi_deinit(void)
{
    return 1;
}

uint8_t bme280_interface_spi_read(uint8_t reg, uint8_t *buf, uint16_t len)
{
    return 1;
}

uint8_t bme280_interface_spi_write(uint8_t reg, uint8_t *buf, uint16_t len)
{
    return 1;
}

/* --------------- 延时与调试输出 --------------- */

void bme280_interface_delay_ms(uint32_t ms)
{
    while (ms)
    {
        unsigned int slice = (ms > 1000U) ? 1000U : (unsigned int)ms;
        usleep(slice * 1000U);
        ms -= slice;
    }
}

void bme280_interface_debug_print(const char *const fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    vprintf(fmt, args);
    va_end(args);
}

编写Makefile

CC = gcc
CFLAGS = -Wall -O2
SRCS = $(wildcard *.c)
OBJS = $(SRCS:.c=.o)
TARGET = bme280_demo

$(TARGET): $(OBJS)
	$(CC) -o $@ $^

%.o: %.c
	$(CC) $(CFLAGS) -c $< -o $@

.PHONY: clean
clean:
	rm -f $(OBJS) $(TARGET)