[讨论]

HC-SR04超声波测距模块调试方法

2019-2-14 16:16:38 3588 Firefly RK3308 RAM 传感器

0 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"; }; 复制代码 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; 复制代码中断处理 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; } 复制代码* 完整的驱动文件可进入Firefly开发者社区下载。 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 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 [url=home.php?mod=space&uid=1999721]@@[/url] -53,6 +53,7 @@ source "drivers/iio/dac/Kconfig" source "drivers/iio/frequency/Kconfig" source "drivers/iio/gyro/Kconfig" source "drivers/iio/humidity/Kconfig" +source "drivers/iio/ultrasonic/Kconfig" 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/ +obj-y += ultrasonic/ obj-y += imu/ obj-y += light/ 复制代码 cd kernel/ make menuconfig 复制代码输入上面的命令，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 +CONFIG_SR04=y CONFIG_ROCKCHIP_SARADC=y CONFIG_PWM=y CONFIG_PWM_ROCKCHIP=y 复制代码配置好后，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 复制代码 Firefly开发者社区可下载附件 0
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