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--- products:sbc:common:applications:gpio:pwm [2022/06/29 21:51]
127.0.0.1 external edit
+++ products:sbc:common:applications:gpio:pwm [2023/03/30 06:35]
ivan [PWM Reference Table]
@@ Line 1: / Line 1: @@
-# PWM
+====== PWM ======
+===== Introduction =====
+This page introduces the usage of hardware PWM, and leads you to control the hardware PWM on the [[products:sbc:common:applications:gpio:40pin-header|40-Pin Header]].
+===== PWM Reference Table =====
+|           ^  PWM       ^  PIN  ^  GPIO name  ^  GPIO num  ^  DT overlay node  ^  Device node              ^
+^  VIM1     |  ''PWM_AO_A''  |  35   |  ''GPIOAO_3''   |  504          |  ''pwm_ao_a''          |  /sys/class/pwm/pwmchip4  |
+^  VIM2     |  ''PWM_D''     |  35   |  ''GPIODV_28''  |  478          |  ''pwm_d''             |  /sys/class/pwm/pwmchip1  |
+^  VIM3/3L  |  ''PWM_F''     |  35   |  ''GPIOH_5''    |  432          |  ''pwm_f''             |  /sys/class/pwm/pwmchip4  |
+^  VIM4     |  ''PWM_F''     |  35   |  ''GPIOY_8''    |  482          |  ''pwm_f''             |  /sys/class/pwm/pwmchip4  |
+^  VIM1S    |  ''PWM_F''     |  35   |  ''GPIOZ_6''    |  503          |  ''pwm_f''             |  /sys/class/pwm/pwmchip0  |
+===== Enable PWM =====
+In order to use the PWM, you need to enable the PWM function via [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].
+<tabbox VIM1/2/3/3L/Edge1>
+Edit ''/boot/env.txt'' to add the pwm node to ''overlays'' node if it doesn't exist.
+Take VIM3 as an example to enable ''PWM_F'', you need to add ''pwm_f'' node to ''overlays'' node if it doesn't exist.
+```shell
+overlays=uart4 pwm_ao_a pwm_f
+```
+After reboot, you will see the pwm device node.
+```shell
+$ ls /sys/class/pwm/pwmchip4
+device  export  npwm  power  subsystem  uevent  unexport
+```
+<tabbox VIM4>
+Edit ''/boot/dtb/amlogic/kvim4.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.
+You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.
+```shell
+fdt_overlays=pwm_f
+```
+After reboot, you will see the pwm device node.
+```shell
+$ ls /sys/class/pwm/pwmchip4
+device  export  npwm  power  subsystem  uevent  unexport
+```
+<tabbox VIM1S>
+Edit ''/boot/dtb/amlogic/kvim1s.dtb.overlay.env'' to add pwm node to ''fdt_overlays'' node if it doesn't exist.
+You need to add ''pwm_f'' to node ''fdt_overlays'' if it doesn't exist to enable ''PWM_F''.
+```shell
+fdt_overlays=pwm_f
+```
+After reboot, you will see the pwm device node.
+```shell
+$ ls /sys/class/pwm/pwmchip0
+device  export  npwm  power  subsystem  uevent  unexport
+```
+</tabbox>
+===== Disable PWM to Use GPIO =====
+If you want to use normal GPIO instead of PWM, you can remove the PWM node in [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].
+===== Control PWM =====
+**Enable PWM:**
+<tabbox VIM1/3/3L/4>
+```shell
+echo 1 | sudo tee /sys/class/pwm/pwmchip4/export
+echo 1000000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/period
+echo 500000 | sudo tee /sys/class/pwm/pwmchip4/pwm1/duty_cycle
+echo 1 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
+```
+<tabbox VIM2>
+```shell
+echo 1 | sudo tee /sys/class/pwm/pwmchip1/export
+echo 1000000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/period
+echo 500000 | sudo tee /sys/class/pwm/pwmchip1/pwm1/duty_cycle
+echo 1 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
+```
+<tabbox VIM1S>
+```shell
+echo 1 | sudo tee /sys/class/pwm/pwmchip0/export
+echo 1000000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/period
+echo 500000 | sudo tee /sys/class/pwm/pwmchip0/pwm1/duty_cycle
+echo 1 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable
+```
+</tabbox>
+Use an oscilloscope to check if the pins have been successfully enabled.
+{{products:sbc:common:applications:gpio:pwm-oscilloscope.png|pwm-oscilloscope}}
+<WRAP info >
+If you use an oscilloscope to view the PWM waveform, remember that the SBC and the oscilloscope need to share the same GND (ground).
+</WRAP>
+**Disable PWM:**
+<tabbox VIM1/3/3L/4>
+```shell
+echo 0 | sudo tee /sys/class/pwm/pwmchip4/pwm1/enable
+```
+<tabbox VIM2>
+```shell
+echo 0 | sudo tee /sys/class/pwm/pwmchip1/pwm1/enable
+```
+<tabbox VIM1S>
+```shell
+echo 0 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable
+```
+</tabbox>

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