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Linux Device Drivers Development

You're reading from   Linux Device Drivers Development Develop customized drivers for embedded Linux

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Product type Paperback
Published in Oct 2017
Publisher Packt
ISBN-13 9781785280009
Length 586 pages
Edition 1st Edition
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Author (1):
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John Madieu John Madieu
Author Profile Icon John Madieu
John Madieu
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Table of Contents (23) Chapters Close

Preface 1. Introduction to Kernel Development FREE CHAPTER 2. Device Driver Basis 3. Kernel Facilities and Helper Functions 4. Character Device Drivers 5. Platform Device Drivers 6. The Concept of Device Tree 7. I2C Client Drivers 8. SPI Device Drivers 9. Regmap API – A Register Map Abstraction 10. IIO Framework 11. Kernel Memory Management 12. DMA – Direct Memory Access 13. The Linux Device Model 14. Pin Control and GPIO Subsystem 15. GPIO Controller Drivers – gpio_chip 16. Advanced IRQ Management 17. Input Devices Drivers 18. RTC Drivers 19. PWM Drivers 20. Regulator Framework 21. Framebuffer Drivers 22. Network Interface Card Drivers

PWM Drivers

Pulse Wide Modulation (PWM) operates like a switch that constantly cycles on and off. It is a hardware feature used to control servomotors, for voltage regulation and so on. The most well-known applications of PWM are:

  • Motor speed control
  • Light dimming
  • Voltage regulation

Now, let's introduce PWM with a simple diagram:

The preceding figure describes a complete PWM cycle, introducing some terms we need to clarify prior to getting deeper into the kernel PWM framework:

  • Ton: This is the duration during which the signal is high.
  • Toff: This is the duration during which the signal is low.
  • Period: This is the duration of a complete PWM cycle. It represents the sum of Ton and Toff of the PWM signal.
  • Duty cycle: It is represented as a percentage of the time signal that remains on during the period of the PWM signal.

Different formulas are detailed as follows:

  • PWM period...
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