利用51单片机的两个定时器同时产生两路脉冲，其中一路为频率、占空比可调的PWM，另一路可以串行发送给定数据（即载波）。-The use of 51 single-chip timer at the same time the two have a two-way pulse, in which all the way for the frequency, duty cycle adjustable PWM, another way can be sent to the set of serial