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126 lines
3.9 KiB
Diff
126 lines
3.9 KiB
Diff
From e94e761305fa2281718adcf625d78f3cf662e12d Mon Sep 17 00:00:00 2001
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From: Dave Stevenson <dave.stevenson@raspberrypi.com>
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Date: Thu, 1 Aug 2024 18:12:50 +0100
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Subject: [PATCH 1206/1215] dtoverlays: Add overlay for HD44780 via I2C PCF8574
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backpack
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Many HD44780 LCD displays are connected via very common I2C
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GPIO expander.
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We have an overlay for connecting the displays directly to GPIOs,
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but not one for it connected via a backpack. Add such an overlay.
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Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
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---
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arch/arm/boot/dts/overlays/Makefile | 1 +
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arch/arm/boot/dts/overlays/README | 27 +++++++++
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.../dts/overlays/hd44780-i2c-lcd-overlay.dts | 57 +++++++++++++++++++
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3 files changed, 85 insertions(+)
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create mode 100644 arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts
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--- a/arch/arm/boot/dts/overlays/Makefile
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+++ b/arch/arm/boot/dts/overlays/Makefile
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@@ -82,6 +82,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
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gpio-no-irq.dtbo \
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gpio-poweroff.dtbo \
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gpio-shutdown.dtbo \
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+ hd44780-i2c-lcd.dtbo \
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hd44780-lcd.dtbo \
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hdmi-backlight-hwhack-gpio.dtbo \
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hifiberry-amp.dtbo \
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--- a/arch/arm/boot/dts/overlays/README
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+++ b/arch/arm/boot/dts/overlays/README
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@@ -1705,6 +1705,33 @@ Params: gpio_pin GPIO pin
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(default 100)
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+Name: hd44780-i2c-lcd
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+Info: Configures an HD44780 compatible LCD display connected via a PCF8574 as
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+ is often found as a backpack interface for these displays.
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+Load: dtoverlay=hd44780-i2c-lcd,<param>=<val>
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+Params: addr I2C address of PCF8574
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+ pin_d4 GPIO pin for data pin D4 (default 4)
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+
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+ pin_d5 GPIO pin for data pin D5 (default 5)
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+
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+ pin_d6 GPIO pin for data pin D6 (default 6)
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+
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+ pin_d7 GPIO pin for data pin D7 (default 7)
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+
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+ pin_en GPIO pin for "Enable" (default 2)
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+
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+ pin_rs GPIO pin for "Register Select" (default 0)
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+
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+ pin_rw GPIO pin for R/W select (default 1)
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+
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+ pin_bl GPIO pin for enabling/disabling the display
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+ backlight. (default 3)
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+
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+ display_height Height of the display in characters (default 2)
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+
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+ display_width Width of the display in characters (default 16)
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+
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+
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Name: hd44780-lcd
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Info: Configures an HD44780 compatible LCD display. Uses 4 gpio pins for
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data, 2 gpio pins for enable and register select and 1 optional pin
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--- /dev/null
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+++ b/arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts
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@@ -0,0 +1,57 @@
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+/dts-v1/;
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+/plugin/;
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+
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+/ {
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+ compatible = "brcm,bcm2835";
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+
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+ fragment@0 {
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+ target = <&i2c_arm>;
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+ __overlay__ {
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+ status = "okay";
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+
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+ pcf857x: pcf857x@27 {
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+ compatible = "nxp,pcf8574";
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+ reg = <0x27>;
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+ gpio-controller;
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+ #gpio-cells = <2>;
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+ status = "okay";
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+ };
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+ };
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+ };
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+
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+ fragment@1 {
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+ target-path = "/";
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+ __overlay__ {
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+ lcd_screen: auxdisplay {
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+ compatible = "hit,hd44780";
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+
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+ data-gpios = <&pcf857x 4 0>,
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+ <&pcf857x 5 0>,
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+ <&pcf857x 6 0>,
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+ <&pcf857x 7 0>;
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+ enable-gpios = <&pcf857x 2 0>;
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+ rs-gpios = <&pcf857x 0 0>;
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+ rw-gpios = <&pcf857x 1 0>;
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+ backlight-gpios = <&pcf857x 3 0>;
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+
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+ display-width-chars = <16>;
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+ display-height-chars = <2>;
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+ };
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+ };
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+ };
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+
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+ __overrides__ {
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+ pin_d4 = <&lcd_screen>,"data-gpios:4";
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+ pin_d5 = <&lcd_screen>,"data-gpios:16";
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+ pin_d6 = <&lcd_screen>,"data-gpios:28";
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+ pin_d7 = <&lcd_screen>,"data-gpios:40";
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+ pin_en = <&lcd_screen>,"enable-gpios:4";
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+ pin_rs = <&lcd_screen>,"rs-gpios:4";
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+ pin_rw = <&lcd_screen>,"rw-gpios:4";
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+ pin_bl = <&lcd_screen>,"backlight-gpios:4";
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+ display_height = <&lcd_screen>,"display-height-chars:0";
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+ display_width = <&lcd_screen>,"display-width-chars:0";
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+ addr = <&pcf857x>,"reg:0";
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+ };
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+
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+};
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