1. [Lab10] Output PWM  Output PWM Signal  Example  Exercise(Optional)

2. PWM  PWM, Pulse Width Modulation. It enable us to contral dc motors, servo motors, fans… etc.  PyBBIO provides 4 PWM pins output which is P9_14, P9_18, P8_13 and P8_19.

3. PWM  The circuit illustrates below Device PWM Pin GND

4. PWM  The PWM output action depends on the integer we give to PWM pins which between 0 to 255.  Pass the integer to PWM by function analogWrite(PWM, value), which is discribe in bbio.py

5. PWM  Example:  In this lecture, we are going to generate an PWM signal by Beaglebone.  Use led as the target of PWM signal.  Give different value to PWM output and observe the brightness of led.

6. Analog Reader(ADC)  Circuit: LED P9_14 (PWM1A) GND

7. Analog Reader(ADC)  Code: from bbio import * brightness = 0 inc = 1 pass = 10 def setup(): pass def loop(): global brightness, inc analogWrite(PWM1A, brightness) brightness += inc if( (brightness==0) or (brightness == 255) ) inc*= -1 delay = pass run(setup, loop)

8.  Exercise:  Use ADC to receive an external signal and change the brightness of led refers to external signal.  Be careful as you did in last week. PWM

9. Pin Configuration

10. VDD_ADC 1.8v AIN0 VR 10K Ω GND_ADC  Circuit2 PWM LED P9_14 (PWM1A) GND

11.  Code: from bbio import * def setup(): pass def loop(): brightness = analogRead(AIN0) *255/4096 analogWrite(PWM1A, brightness) delay(10) run( setup, loop) PWM

12.  Tune the resistor and observe the led changes. PWM

13. END