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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 [2024/08/22 02:40] (current)
nick
@@ 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      ^  DT overlay node  ^  Device node              ^
+^  VIM1   |  ''PWM_AO_A''  |  35   |  ''GPIOAO_3''   |  ''pwm_ao_a''     |  /sys/class/pwm/pwmchip4  |
+^  VIM2   |  ''PWM_D''     |  35   |  ''GPIODV_28''  |  ''pwm_d''        |  /sys/class/pwm/pwmchip1  |
+^  VIM3   |  ''PWM_F''     |  35   |  ''GPIOH_5''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip4  |
+^  VIM3L  |  ''PWM_F''     |  35   |  ''GPIOH_5''    |  ''pwm_f''        | /sys/class/pwm/pwmchip0   |
+^  VIM4   |  ''PWM_F''     |  35   |  ''GPIOY_8''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip4  |
+^  VIM1S  |  ''PWM_F''     |  35   |  ''GPIOZ_6''    |  ''pwm_f''        |  /sys/class/pwm/pwmchip0  |
+===== Enable PWM =====
+==== Linux ====
+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/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=uart3 pwm_f i2c3 i2s os08a10 watchdog
+```
+After reboot, you will see the pwm device node.
+```shell
+$ ls /sys/class/pwm/pwmchip4
+device  export  npwm  power  subsystem  uevent  unexport
+```
+<tabbox VIM3L>
+Edit ''/boot/env.txt'' to add the pwm node to ''overlays'' node if it doesn't exist.
+Take VIM3L as an example to enable ''PWM_F'', you need to add ''pwm_f'' node to ''overlays'' node if it doesn't exist.
+```shell
+overlays=uart3 pwm_f i2c3 i2s watchdog
+```
+After reboot, you will see the pwm device node.
+```shell
+$ ls /sys/class/pwm/pwmchip0
+device  export  npwm  power  subsystem  uevent  unexport
+```
+<tabbox VIM3 with 5.15 kernel>
+Edit ''/boot/dtb/amlogic/kvim3.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.
+<tabbox VIM3L with 5.15 kernel>
+Edit ''/boot/dtb/amlogic/kvim3l.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.
+<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>
+==== Android ====
+<tabbox VIM4>
+The ''PWM'' function is disabled by default, you need to modify the dts to enable it.
+```diff
+diff --git a/arch/arm64/boot/dts/amlogic/kvim4.dts b/arch/arm64/boot/dts/amlogic/kvim4.dts
+--- a/arch/arm64/boot/dts/amlogic/kvim4.dts
++++ b/arch/arm64/boot/dts/amlogic/kvim4.dts
+ &pwm_ef {
++    pinctrl-names = "default";
++    pinctrl-0 = <&pwm_f_pins>;
+        status = "okay";
+ };
+diff --git a/arch/arm64/boot/dts/amlogic/kvim4n.dts b/arch/arm64/boot/dts/amlogic/kvim4n.dts
+--- a/arch/arm64/boot/dts/amlogic/kvim4n.dts
++++ b/arch/arm64/boot/dts/amlogic/kvim4n.dts
+ &pwm_ef {
++    pinctrl-names = "default";
++    pinctrl-0 = <&pwm_f_pins>;
+        status = "okay";
+ };
+diff --git a/arch/arm64/boot/dts/amlogic/mesont7_an400-panel.dtsi b/arch/arm64/boot/dts/amlogic/mesont7_an400-panel.dtsi
+--- a/arch/arm64/boot/dts/amlogic/mesont7_an400-panel.dtsi
++++ b/arch/arm64/boot/dts/amlogic/mesont7_an400-panel.dtsi
+@@ -1442,13 +1442,13 @@
+        backlight1{
+                compatible = "amlogic, backlight-t7";
+-               status = "okay";
++               status = "disabled";
+                index = <1>;
+                key_valid = <0>;
+                pinctrl-names = "pwm_on",
+                                "pwm_off";
+-               pinctrl-0 = <&pwm_f_pins>;
+-               pinctrl-1 = <&bl1_pwm_off_pins>;
+                pinctrl_version = <2>; /* for uboot */
+                interrupts = <0 197 1
+```
+<tabbox VIM1S>
+The ''PWM'' function is disabled by default, you need to modify the dts to enable it.
+```diff
+--- a/arch/arm64/boot/dts/amlogic/kvim1s.dts
++++ b/arch/arm64/boot/dts/amlogic/kvim1s.dts
+@@ -1411,8 +1411,8 @@
+ };
+ &pwm_ef {
+-       /*pinctrl-0 = <&pwm_f_pins2>;*/
+-       /*pinctrl-names = "default";*/
++       pinctrl-0 = <&pwm_f_pins2>;
++       pinctrl-names = "default";
+        status = "okay";
+ };
+```
+</tabbox>
+===== Control PWM =====
+**Enable PWM:**
+<tabbox VIM1/3/4>
+```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 VIM3L/1S>
+```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 VIM1/3/4>
+```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 VIM3L/1S>
+```shell
+echo 0 | sudo tee /sys/class/pwm/pwmchip0/pwm1/enable
+```
+</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]].

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