How to add pwm - Revision history

LubOlimex: /* How to enable PWM libraries for Olimex Allwinner boards */

2015-10-01T10:47:34Z

‎How to enable PWM libraries for Olimex Allwinner boards

LubOlimex: LubOlimex moved page How-to-add-pwm-sunxi to How to add pwm: easier for access

2014-01-13T12:48:22Z

LubOlimex moved page How-to-add-pwm-sunxi to How to add pwm: easier for access

LubOlimex: /* How to enable PWM libraries for Olimex Allwinner boards */

2014-01-13T12:42:26Z

‎How to enable PWM libraries for Olimex Allwinner boards

LubOlimex: Created page with "===How to enable PWM libraries for Olimex Allwinner boards=== The article describes how to enable the PWM control in the Olimex Allwinner boards under Linux by enabling the "..."

2014-01-13T12:30:44Z

Created page with "===How to enable PWM libraries for Olimex Allwinner boards=== The article describes how to enable the PWM control in the Olimex Allwinner boards under Linux by enabling the "..."

New page

===How to enable PWM libraries for Olimex Allwinner boards===

The article describes how to enable the PWM control in the Olimex Allwinner boards under Linux by enabling the "Sunxi PWM Driver" in the kernel.

If the Linux PWM module in the board you are using is not available for use there is a good chance it is not enabled by default in the distribution you are using. A way to enable it is detailed below.

To enable the PWM module you need to perform five major steps:

1. Recompile the kernel following one of the Olimex wordpress guides for the board you have on how to do it. The only difference would be to enable the "Sunxi PWM Driver (pwm-sunxi)" as shown in the picture below.

[[File:Pwm_enable2.jpg]]

2. Replace the uImage file from first partition of your SD card with the generated one from ../linux-sunxi/arch/arm/boot/uImage directory

3. Replace the modules from second partition of your SD card (usualy they are located in /lib/modules/xx.xx.x) with the new generated modules from ../linux-sunxi/out/modules/xx.xx.x

if the PWM module is not loaded you can load it with

<nowiki>#modprobe pwm-sunxi</nowiki>

4. Edit the script.fex in the "[pwm0_para]" paragraph adding PWM support for specific pin.

Example config for script.bin:

[pwm0_para]

pwm_used = 1

pwm_period = 10000

pwm_duty_percent = 100

Source and more info on the subject: [https://groups.google.com/d/msg/linux-sunxi/BYEGz3ZRxx4/YwZxMvLobfQJ google sunxi groups discussion on pwm0_para]

5. Boot the board and use the library! Info on the pwm class:

- /sys/class/pwm-sunxi
|
+----pwmX
|
+---duty
+---duty_percent
+---period
+---polarity
+---pulse
+---pin
+---run

Information on the parameters:

'''period (r/w)'''
- period that makes up a cycle. Can be expressed as hz, khz, ms, or us. Whole numbers only.

Examples:
echo 10hz > /sys/class/pwm-sunxi/pwm0/period
echo 1khz > /sys/class/pwm-sunxi/pwm0/period
echo 100ms > /sys/class/pwm-sunxi/pwm0/period
echo 100us > /sys/class/pwm-sunxi/pwm0/period
echo 150khz > /sys/class/pwm-sunxi/pwm0/period

'''duty (r/w)'''
- portion of the period above that is "active" or on. Same units as above.
Examples:
echo 1hz > /sys/class/pwm-sunxi/pwm0/period
echo 2hz > /sys/class/pwm-sunxi/pwm0/duty

'''duty_percent (r/w)'''
- duty (above) expressed as a percentage. Whole numbers only
Example:
echo 50 > /sys/class/pwm-sunxi/pwm0/duty_percent

'''polarity(r/w)'''
- polarity of the pin during the duty portion. 1 = high, 0 = low

'''pulse (r/w)'''
- output one pulse at the specified period and duty

Source and more info on the subject: [https://groups.google.com/d/msg/linux-sunxi/I81t60tLgcA/3z26wqyrPaAJ google sunxi group discussion on PWM kernel module]

@@ Line 47: / Line 47: @@
                                +---run
-Information on the parameters:
+'''Information on the parameters:'''
 '''period (r/w)'''
@@ Line 75: / Line 75: @@
 '''pulse (r/w)'''
 - output one pulse at the specified period and duty
 Source and more info on the subject: [https://groups.google.com/d/msg/linux-sunxi/I81t60tLgcA/3z26wqyrPaAJ google sunxi group discussion on PWM kernel module]

← Older revision	Revision as of 12:48, 13 January 2014
(No difference)

@@ Line 66: / Line 66: @@
 '''duty_percent (r/w)'''
-- duty (above) expressed as a percentage. Whole numbers only
+- duty (above) expressed as a percentage. Whole numbers only.
          Example:
          echo 50 > /sys/class/pwm-sunxi/pwm0/duty_percent