按航模通道控制PPM信号要求做的一个测试仪，可测试舵机和电调无刷电机等。输出信号周期为20mS，高电平变化量为1mS~2mS。通过按键实现手动测试、自动回中、自动测试功能。（刚开始对航模感兴趣，初学编程所做的小玩意儿）(A testing instrument for controlling the PPM signal according to the channel channel can be used to test the rudder and electric brushless motor. The output signal period is 20mS, and the high level change is 1mS~2mS. The function of manual test, automatic return and automatic test is realized through key press. (just beginning to be interested in the model, a little gadget for initial programming))