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litesom:devicetree:lcd [2017/02/13 19:58] filug [PWM- Backlight] |
litesom:devicetree:lcd [2017/08/17 11:04] filug [Backlight] |
====== i.MX6UL and LCD display ====== | ====== liteSOM and LCD display ====== |
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| <well> |
| {{:github-mark-32px.png?nolink |}} |
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| Example available on [[https://github.com/grinn-pub/examples|GitHub]]. |
| Check [[https://github.com/grinn-pub/examples/blob/master/configs/grinn_liteboard_lcd_res_defconfig|liteboard LCD + touchscreen]]. |
| </well> |
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<columns 100% 50% - -> | <columns 100% 50% - -> |
* ''PWM'' - <tooltip title="to control LCD display backlight">Pulse Width Modulation</tooltip>. | * ''PWM'' - <tooltip title="to control LCD display backlight">Pulse Width Modulation</tooltip>. |
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Below you can see how to configure [[litesom:liteboard]] to support [[emv:lcd]] module. | Below you can see how to configure [[litesom:liteboard]] to support [[devices:lcd]] module. |
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<alert type="info">Complete example for [[litesom:liteboard]] and [[emv:lcd]] you can find on our [[https://github.com/grinn-pub/examples|GitHub examples repository]].</alert> | <alert type="info">Complete example for [[litesom:liteboard]] and [[devices:lcd]] you can find on our [[https://github.com/grinn-pub/examples|GitHub examples repository]].</alert> |
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On [[evm:lcd]] we are using [[https://riverdi.com/product/rvt7-0a800480tnwr00/|RVT7.0A800480TNWR00]] TFT display produced by [[https://riverdi.com/|Riverdi]]. Below you can find short details about this device: | On [[evm:lcd]] we are using [[https://riverdi.com/product/rvt7-0a800480tnwr00/|RVT7.0A800480TNWR00]] TFT display produced by [[https://riverdi.com/|Riverdi]]. Below you can find short details about this device: |
* touchscreen: resistive. | * touchscreen: resistive. |
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| FIXME LCD part number |
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</columns> | </columns> |
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===== Backlight ===== | ===== Backlight ===== |
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| <columns 100% 45% - -> |
| <uml> |
| package "liteboard" { |
| [PWM backlight driver] -> [PWM] |
| } |
| package "Display" { |
| [PWM] -> [Backlight] |
| } |
| </uml> |
| |
| <code> |
| / { |
| backlight { |
| compatible = "pwm-backlight"; |
| pwms = <&pwm2 0 5000000>; |
| brightness-levels = <0 4 8 16 32 64 128 255>; |
| default-brightness-level = <6>; |
| status = "okay"; |
| }; |
| }; |
| |
| &iomuxc { |
| pinctrl_pwm2: pwm2 { |
| fsl,pins = < |
| MX6UL_PAD_GPIO1_IO09__PWM2_OUT 0x110b0 |
| >; |
| }; |
| }; |
| |
| &pwm2 { |
| pinctrl-names = "default"; |
| pinctrl-0 = <&pinctrl_pwm2>; |
| status = "okay"; |
| clocks = <&clks IMX6UL_CLK_PWM2>, |
| <&clks IMX6UL_CLK_PWM2>; |
| }; |
| </code> |
| <newcolumn> |
| |
| On [[litesom:liteboard]] you can find dedicated LCD backlight boot converter (see [[http://www.ti.com/product/TPS61042|TPS61042]]) controlled by [[:litesom]] via ''PWM2 output'' pin. |
| |
| {{ :litesom:devicetree:litesom_backlight_driver.png?500 |}} |
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| Backlight can be controlled directly via ''PWM driver'' but additional ''PWM backlight driver'' will <tooltip title="from software point of view">simplify</tooltip> backlight configuration. |
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| Node ''backlight'' is documented in [[https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt|pwm-backlight.txt]] file. |
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| Backlight configured as presented here will: |
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| * generate PWM with 200Hz frequency (period 5000000 ns), |
| * use ''PWM2'' peripheral as backlight controller, |
| * define eight allowed backlight levels: 0%, 2%, 3%, 6%, 13%, 25%, 50%, 100%, |
| * use 50% as default backlight level. |
| |
| Node ''pinctrl_pwm2'' is information for ''IOMUX controller'' how to configure ''PWM2'' output. On [[litesom:liteboard]] we are using ''GPIO1__IO09''. |
| |
| {{ :litesom:devicetree:litesom_backlight.png?400 |}} |
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| Node ''pwm2'' is configured as documented in [[https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pwm/pwm.txt|pwm.txt]]. |
| </columns> |
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