Micro USB DC 2CH Adjustable PWM Signal Generator DIY Duty Cycle Pulse Frequency Module Digital LED Display Tube 5V 12V 24V 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.