Highlights:
    Two independent PWM generators can set the frequency, duty cycle;
    The wide frequency range, high accuracy;
    Can serial communication.
First, the module description：

Frequency is divided into three ranges:
    XXX (no decimal point): the smallest unit is 1Hz, the range 1Hz ~ 999Hz;
    XX.X (decimal point in ten): The minimum unit is 0.1Khz; the range of 0.1KHz ~ 99.9KHz
    X.X.X. (there are three decimal point): the smallest unit is 1Khz; the range 1KHz ~ 150KHz

Frequency display example:
"100" indicates that the PWM output pulse of 100Hz;
"54.1" indicates that the PWM output pulse of 54.1KHz;
"1.2.4." Indicates that the PWM pulse output 124KHz
Duty Cycle in the range: 0 to 100;
Three frequencies duty cycle is the same, all the parameters non-volatile.

Second, the module parameters:
    Working voltage: 5--30V, support micro USB 5.0V power supply;
    Frequency range: 1Hz ~ 150KHz;
    The frequency accuracy: ± 2%;
    Output Current: <30mA;
    Output amplitude: Default 5Vp-p (settable);
    Operating temperature range: -30 ~ + 70 ℃.

Third, the parameter settings：

Module has three buttons [Set], [Up], [Down];
    Press [Set] key to switch the display four parameters (FR1: PWM1 frequency; dU1: PWM1 duty cycle; FR2: frequency of PWM2; dU2: PWM2 duty cycle), before the handover parameters, there will be corresponding parameter name flash.
    Press [Up], [Down] keys to modify the current parameter value (long press can quickly add or subtract fast).
    Two PWM each have three preset frequency, the frequency display interface, long press [SET] key to switch between three types of frequencies, three kinds of frequency duty cycle is the same value. (XXX: range 1Hz ~ 999Hz; XX.X: range 0.1Khz ~ 99.9Khz; X.X.X .: range 1Khz ~ 150Khz,).

Fourth, the scope:
    As square wave signal generator which generates a square wave signal;
    to provide a signal to the stepping motor driver;
    Adjustable pulse generation for chip use;
    produce variable pulse signal, the control-related circuit (PWM dimming, speed).

Fifth, the serial control
Baud rate: 9600 bps
Data bits: 8
Stop bits: 1
Parity bit: none
Flow control: none
1, set the PWM frequency
"S1FXXXT": setting PWM1 frequency of XXX HZ (001 ~ 999)
"S1FXX.XT": set the frequency of PWM1 XX.X KHZ (00.1 ~ 99.9)
"S1F: X.X.X.T": setting PWM1 frequency of XXX KHZ (0.0.1 ~ 1.5.0..)
'S1': PWM1
'S2': PWM2
'F': Frequency
'D': Duty Cycle
'T' is the end flag
    Set the PWM duty cycle
"S1DXXXT": setting PWM1 duty cycle XXX; (001 ~ 100)
"S2DXXXT": set PWM2 duty cycle XXX; (001 ~ 100)
Setting successful return: DOWN;
Setting failback: FALL