In this exercise you will learn how to use the Beagle’s pulse width modulation pwm hardware using the sysfs interface and also learn about pin multiplexing pin mux on the way. This says the MUX is presently set on pin 7. If these command cause the SSH connection to close, you may have to get a newer version of Angstrom. Although this approach works, it is really transitional until a standard can be established. If it isn’t you’ll have to recompile the Kernel and u-boot. How do you know which one to change? I couldn’t set them during kernel boot with the 2.

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I couldn’t set them during kernel boot with the 2.

EBC Exercise 13 Pulse Width Modulation 3.2

Here’s another PWM lead. The standard way to interface with the outside world in Linux is through Kernel Drivers.

Can you guess why? A given pin can have one from as many as eight lines assigned to it. What’s the highest frequency you can get? The DM has 11 general purpose timers, 4 of which gpt8-gpt11 can be brought out of the chip and used for pulse width modulation DM TRM page Stick a scope on the pin and see if the frequency and duty cycle are right.

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This says the MUX is presently set on pin 7.

You may have to set the duty cycle to 0 to change the frequency. These MUXes are set at boot time, and must be set when the kernel boots, ehrpwk in u-boot.

You could even do PWM from a shell command by using devmem2 to write to the memory mapped registers from a command line. Navigation menu Personal tools Log in Request account.

AMx PWM Driver’s Guide – Texas Instruments Wiki

Follow the instructions here if you aren’t set up for git. This page was last edited on 31 Mayat How do you know which one to change?

Counting starts on the left with 0.

Currently there are no standard PWM driver for the Beagle, though a couple have been proposed [1][2] and [3]. We want pin 6.

In this exercise you will learn how to use the Beagle’s pulse width modulation pwm hardware using the sysfs interface and also learn about pin multiplexing pin mux on the way. If it isn’t you’ll have to recompile the Kernel and u-boot. You’ll see something like:. Embedded Linux Class by Mark A. I was able to get a 1. Views Read View source View history.

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The version of the kernel and u-boot that I’ve given you should already be configured to access the PWM pins. Although this approach works, it is really transitional until a standard can be established.

The u-boot details are here. Privacy policy About eLinux.

Linux source code: drivers/pwm/pwm-tiehrpwm.c (v) – Bootlin

Retrieved from ” https: If these command cause the SSH connection to close, you may have to get a newer version of Angstrom. In a previous exercise EBC Exercise 11 gpio Polling and Interrupts you saw how to use the gpio to produce a square wave out linuux a C program and sysfs. This will show up at ehrpwm1A the 0 maps to A.

Try changing the frequency and duty cycle. Now, check the settings by browsing to http: