Ameba MicroPython: [RTL8722CSM] [RTL8722DM] PWM
class PWM – Pulse Width Modulation
Examples
LED fade:
• Materials: Ameba x 1, LED x 1, resistor(220ohm) x 1
• Steps:
PWM use pulse width modulation to control output duty cycle and is widely used to control LED brightness and motor. Here we are using an LED to demonstrate how PWM works.
Let us connect pin PA_26 to the anode leg of an LED which in series with a current limiting resistor and GND to cathode of the LED as shown below
Then, copy and paste the following code line by line into REPL and hit Enter. If everything is in order, you should be able to see the LED slowly become brighter as you paste another line of code.
from machine import Pin, PWM import time p = PWM(pin = "PA_26") # 0 duty cycle thus output 0 p.write(0.0) # 10% duty cycle p.write(0.1) # 50% duty cycle p.write(0.5) # 100% duty cycle p.write(1.0)
API Documents
Constructors
PWM(unit [optional], “pin_name” [required])
Create a PWM object associated with the given pin name. This allows you to then write PWM signal on the pin.
• unit: unit ID of the hardware PWM, will use default unit 0 if leave blank.
• “pin_name”: The name of the pin, must be in string format. See below for PWM supported pins.
Note: PWM is currently only supported on the following pins, PA_23, PA_24, PA_25, PA_26
Methods
PWM.write(dutycycle_float [required])
This method will return the associated GPIO pin name after declaring a Pin object.
Pin.init(“pin_name” [required], direction [required], pull_mode [optional], value [optional])
This method will output a PWM signal with given duty cycle on the associated GPIO pin.
• dutycycle_float: a floating point duty cycle value, can be from 0.0 (0%) to 1.0 (100%)
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