git.ipfire.org Git - thirdparty/openwrt.git/blob

   1 From e94e761305fa2281718adcf625d78f3cf662e12d Mon Sep 17 00:00:00 2001
   2 From: Dave Stevenson <dave.stevenson@raspberrypi.com>
   3 Date: Thu, 1 Aug 2024 18:12:50 +0100
   4 Subject: [PATCH 1206/1215] dtoverlays: Add overlay for HD44780 via I2C PCF8574
   5  backpack
   6
   7 Many HD44780 LCD displays are connected via very common I2C
   8 GPIO expander.
   9 We have an overlay for connecting the displays directly to GPIOs,
  10 but not one for it connected via a backpack. Add such an overlay.
  11
  12 Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
  13 ---
  14  arch/arm/boot/dts/overlays/Makefile           |  1 +
  15  arch/arm/boot/dts/overlays/README             | 27 +++++++++
  16  .../dts/overlays/hd44780-i2c-lcd-overlay.dts  | 57 +++++++++++++++++++
  17  3 files changed, 85 insertions(+)
  18  create mode 100644 arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts
  19
  20 --- a/arch/arm/boot/dts/overlays/Makefile
  21 +++ b/arch/arm/boot/dts/overlays/Makefile
  22 @@ -82,6 +82,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
  23         gpio-no-irq.dtbo \
  24         gpio-poweroff.dtbo \
  25         gpio-shutdown.dtbo \
  26 +       hd44780-i2c-lcd.dtbo \
  27         hd44780-lcd.dtbo \
  28         hdmi-backlight-hwhack-gpio.dtbo \
  29         hifiberry-amp.dtbo \
  30 --- a/arch/arm/boot/dts/overlays/README
  31 +++ b/arch/arm/boot/dts/overlays/README
  32 @@ -1705,6 +1705,33 @@ Params: gpio_pin                GPIO pin
  33                                  (default 100)
  34
  35
  36 +Name:   hd44780-i2c-lcd
  37 +Info:   Configures an HD44780 compatible LCD display connected via a PCF8574 as
  38 +        is often found as a backpack interface for these displays.
  39 +Load:   dtoverlay=hd44780-i2c-lcd,<param>=<val>
  40 +Params: addr                    I2C address of PCF8574
  41 +        pin_d4                  GPIO pin for data pin D4 (default 4)
  42 +
  43 +        pin_d5                  GPIO pin for data pin D5 (default 5)
  44 +
  45 +        pin_d6                  GPIO pin for data pin D6 (default 6)
  46 +
  47 +        pin_d7                  GPIO pin for data pin D7 (default 7)
  48 +
  49 +        pin_en                  GPIO pin for "Enable" (default 2)
  50 +
  51 +        pin_rs                  GPIO pin for "Register Select" (default 0)
  52 +
  53 +        pin_rw                  GPIO pin for R/W select (default 1)
  54 +
  55 +        pin_bl                  GPIO pin for enabling/disabling the display
  56 +                                backlight. (default 3)
  57 +
  58 +        display_height          Height of the display in characters (default 2)
  59 +
  60 +        display_width           Width of the display in characters (default 16)
  61 +
  62 +
  63  Name:   hd44780-lcd
  64  Info:   Configures an HD44780 compatible LCD display. Uses 4 gpio pins for
  65          data, 2 gpio pins for enable and register select and 1 optional pin
  66 --- /dev/null
  67 +++ b/arch/arm/boot/dts/overlays/hd44780-i2c-lcd-overlay.dts
  68 @@ -0,0 +1,57 @@
  69 +/dts-v1/;
  70 +/plugin/;
  71 +
  72 +/ {
  73 +       compatible = "brcm,bcm2835";
  74 +
  75 +       fragment@0 {
  76 +               target = <&i2c_arm>;
  77 +               __overlay__ {
  78 +                       status = "okay";
  79 +
  80 +                       pcf857x: pcf857x@27 {
  81 +                               compatible = "nxp,pcf8574";
  82 +                               reg = <0x27>;
  83 +                               gpio-controller;
  84 +                               #gpio-cells = <2>;
  85 +                               status = "okay";
  86 +                       };
  87 +               };
  88 +       };
  89 +
  90 +       fragment@1 {
  91 +               target-path = "/";
  92 +               __overlay__ {
  93 +                       lcd_screen: auxdisplay {
  94 +                               compatible = "hit,hd44780";
  95 +
  96 +                               data-gpios = <&pcf857x 4 0>,
  97 +                                            <&pcf857x 5 0>,
  98 +                                            <&pcf857x 6 0>,
  99 +                                            <&pcf857x 7 0>;
 100 +                               enable-gpios = <&pcf857x 2 0>;
 101 +                               rs-gpios = <&pcf857x 0 0>;
 102 +                               rw-gpios = <&pcf857x 1 0>;
 103 +                               backlight-gpios = <&pcf857x 3 0>;
 104 +
 105 +                               display-width-chars = <16>;
 106 +                               display-height-chars = <2>;
 107 +                       };
 108 +               };
 109 +       };
 110 +
 111 +       __overrides__ {
 112 +               pin_d4 = <&lcd_screen>,"data-gpios:4";
 113 +               pin_d5 = <&lcd_screen>,"data-gpios:16";
 114 +               pin_d6 = <&lcd_screen>,"data-gpios:28";
 115 +               pin_d7 = <&lcd_screen>,"data-gpios:40";
 116 +               pin_en = <&lcd_screen>,"enable-gpios:4";
 117 +               pin_rs = <&lcd_screen>,"rs-gpios:4";
 118 +               pin_rw = <&lcd_screen>,"rw-gpios:4";
 119 +               pin_bl = <&lcd_screen>,"backlight-gpios:4";
 120 +               display_height = <&lcd_screen>,"display-height-chars:0";
 121 +               display_width = <&lcd_screen>,"display-width-chars:0";
 122 +               addr = <&pcf857x>,"reg:0";
 123 +       };
 124 +
 125 +};