Description: 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.
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driver.txt
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