ROC-RK3308-CC开发实例总结--HC-SR04超声波测距模块调试

HC-SR04是一款常见的超声波测距传感器，它可以提供2cm-400cm的非接触式测距功能，精度达到3mm，基本可以满足一般测距需求。该款模块的两个IO口，其中trig为触发信号输入，echo为回响信号输出。接下来说说调试方法。
1. dts设备注册
修改 kernel/arch/arm64/boot/dts/rockchip/rk3308-firefly.dtsi 该文件，增加以下资源描述：

sr04_test: sr04_test {
    compatible= "ultrasonic";
    trig-gpios = <&gpio0 RK_PA5 GPIO_ACTIVE_HIGH>;
    echo-gpios = <&gpio0 RK_PC4 GPIO_ACTIVE_HIGH>;
    status = "okay";
};

　　

2. 驱动编写，笔者在iio子系统下进行驱动编写，在路径 kernel/drivers/iio/下创建ultrasonic/，参考这款传感器的规格书，下面是部分驱动代码的实现：
信号触发

        
  ret = gpio_direction_output(sr04->trig, 0);
        if (ret)
               goto err;
        udelay(2);
        ret = gpio_direction_output(sr04->trig, 1);
        if (ret)
               goto err;
        udelay(15);
        ret = gpio_direction_output(sr04->trig, 0);
        if (ret)
               goto err;

　　

中断处理

static irqreturn_t sr04_handle_irq(int irq, void *data)
{
    struct iio_dev *iio = data;
    struct sr04 *sr04 = iio_priv(iio);

    current_echo_value[sr04->number] = gpio_get_value(sr04->echo);
    if (current_echo_value[sr04->number] != last_echo_value[sr04->number]) {
      if(sr04_flag[sr04->number]==0){
            do_gettimeofday(&start[sr04->number]);
            sr04_flag[sr04->number] = 1;
            last_echo_value[sr04->number] = current_echo_value[sr04->number];
      }
      else{
            do_gettimeofday(&end[sr04->number]);
            time_lag[sr04->number] = (end[sr04->number].tv_usec-start[sr04->number].tv_usec);
            sr04_flag[sr04->number] = 0;
            last_echo_value[sr04->number] = current_echo_value[sr04->number];
      }
      ev_press = 1;
      wake_up_interruptible(&sr04_waitq);
    }

    return IRQ_HANDLED;
}

　　

完整的驱动文件可见后面附件。

3. 完成驱动代码编写后，分别修改kernel/drivers/iio/Kconfig b/kernel/drivers/iio/Kconfig和kernel/drivers/iio/Makefile b/kernel/drivers/iio/Makefile

<font color="Black">diff --git a/kernel/drivers/iio/Kconfig b/kernel/drivers/iio/Kconfig
index 66792e7..07fdf91 100644
--- a/kernel/drivers/iio/Kconfig
+++ b/kernel/drivers/iio/Kconfig
@@ -53,6 +53,7 @@ source "drivers/iio/dac/Kconfig"
 source "drivers/iio/frequency/Kconfig"
 source "drivers/iio/gyro/Kconfig"
 source "drivers/iio/humidity/Kconfig"
<font color="Red">+source "drivers/iio/ultrasonic/Kconfig"</font>
 source "drivers/iio/imu/Kconfig"
 source "drivers/iio/light/Kconfig"
 source "drivers/iio/magnetometer/Kconfig"
diff --git a/kernel/drivers/iio/Makefile b/kernel/drivers/iio/Makefile
index aeca726..c409a89 100644
--- a/kernel/drivers/iio/Makefile
+++ b/kernel/drivers/iio/Makefile
@@ -19,6 +19,7 @@ obj-y += dac/
 obj-y += gyro/
 obj-y += frequency/
 obj-y += humidity/
<font color="Red">+obj-y += ultrasonic/</font>
 obj-y += imu/
 obj-y += light/</font>

　　

<font color="Black">cd kernel/
make menuconfig</font>

　　

输入上面的命令，进入图形选择界面，/ 搜索sr04，选择、保存、退出。

--- a/kernel/arch/arm64/configs/firefly-rk3308_linux_defconfig
+++ b/kernel/arch/arm64/configs/firefly-rk3308_linux_defconfig
@@ -251,6 +251,7 @@ CONFIG_IIO=y
 CONFIG_IIO_BUFFER=y
 CONFIG_IIO_KFIFO_BUF=y
 CONFIG_IIO_TRIGGER=y
<font color="Red">+CONFIG_SR04=y</font>
 CONFIG_ROCKCHIP_SARADC=y
 CONFIG_PWM=y
 CONFIG_PWM_ROCKCHIP=y

　　

配置好后，参考官方维基http://wiki.t-firefly.com/ROC-RK ... html#bian-yi-kernel进行编译即可。

编译烧录完成，可以找到我们挂载的设备节点

# cd /sys/bus/iio/devices/iio:device1
# ls
dev     in_temp_input     name     of_node     power     subsystem     uevent

　　

进入Firefly开发者社区，可下载驱动附件