PV198 - Pulse Width Modulation
One-chip Controllers
Daniel Dlhopolček, Marek Vrbka, Jan Koniarik, Oldřich Pecák,
Tomáš Rohlínek, Ján Labuda, Jan Horáček, Matúš Škvarla, Ondřej Bleha,
Martin Klimeš, Adam Valt
Faculty of Informatics, Masaryk University
4/2024
Content
Content
Overview
Modes of Operation
Tasks
Homework
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Overview
Intro
Switch the branch to Week_04!
Discussion of HW3
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Overview
What is PWM
PWM – Pulse Width Modulation
A method of reducing the average power delivered by an
electrical signal, by effectively chopping it up into discrete parts
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Overview
What is it used for
Motor control
Audio amplifiers
Digital lighting
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Overview
How does it work
Switching fast enough for the application
Changing duty cycle
https://commons.wikimedia.org/wiki/File:Duty_Cycle_Examples.png
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Overview
FRDM-K66F PWM capabilities
FlexTimer Module (FTM)
4 instances
2-8 channels
Timer/PWM Module (TPM)
2 instances
2 channels
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Modes of Operation
Timer/PWM Module (TPM)
Modes of operation:
Input capture
Output compare
Edge-Aligned PWM
Center-Aligned PWM
Combined PWM
Combine Input Capture
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Modes of Operation
Input Capture
Detects edge in the input signal
Configurable rising/falling edge detection
Edge sets interrupt flag
Read precise time from counter
Example: ultrasonic distance sensor demo
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Modes of Operation
Output Compare
Generate timed pulses with programmable position, polarity,
duration and frequency
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Modes of Operation
Edge-Aligned PWM
Leading edge is aligned with the beginning of the period
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Modes of Operation
Center-Aligned PWM
Counts up until it reaches MOD and then counts down until it
reaches zero
The pulse width center is when TPM counter = 0
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Tasks
Tasks
1. Create an application that turns on Blue LED with 20% intensity
Use TPM or FTM peripheral
2. Update your application to turn on Green and Red LED with 20%
intensity (notice that TPM is not available)
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Tasks
Stepper motor demo
Which mode can we use to get 4 signals as shown in the picture?
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Homework
Homework - Cycle trough HSV Hue color spectrum
Write three functions that set intensity for each color
Download HSV_RGB.h from the study materials
Periodically iterate over all colors updating: H = (H + 1) % 360
Don’t be too fast, if a whole cycle takes less than 10 seconds,
tests might not pass
If a cycle takes longer than a minute, tests might not pass
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