1. 硬件基于HC-SR04模块，可自行查找。

2. 代码PWM模块用于测试中断响应性能， 背光部分注释掉是因为和PWM复用了。

3. 测试中断响应性能时不要使用在中断上半部使用printk()方式，否则延时会到ms级。

4. 代码中注册的字符设备可不需要，创建的内核线程用于控制时序。

3. 由于超声波采用的是普通的GPIO中断，而且精度需要达到us级，当有许多高优先级的中断需要处理时，

驱动响应会延迟导致得到的时间不同，稳定性会大大下降，只可作为参考，如果要商用最好使用专用单片机模块处理测距。-1 hardware based on the HC-SR04 module, can find.

2 code PWM module is used to test the performance of the interrupt response, the back part of the back light is due to the PWM reuse.

3 test interrupt response performance is not used in the upper half of the use of printk (), otherwise the delay will be to Ms.

4 code in the registration of the character device does not need to create the kernel thread for the control of the timing.

3 due to the use of ultrasound is a common GPIO interrupt, and the accuracy of the need to reach us level, when there are many high priority interrupt needs to be processed,

Drive response will delay the time to get different, stability will be greatly reduced, only as a reference, if you want to use the best commercial use of a dedicated single-chip module processing.