xref: /linux/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.yaml (revision 7255fcc80d4b525cc10cfaaf7f485830d4ed2000) 
1# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2%YAML 1.2
3---
4$id: http://devicetree.org/schemas/auxdisplay/hit,hd44780.yaml#
5$schema: http://devicetree.org/meta-schemas/core.yaml#
6
7title: Hitachi HD44780 Character LCD Controller
8
9maintainers:
10  - Geert Uytterhoeven <geert@linux-m68k.org>
11
12description:
13  The Hitachi HD44780 Character LCD Controller is commonly used on character
14  LCDs that can display one or more lines of text. It exposes an M6800 bus
15  interface, which can be used in either 4-bit or 8-bit mode. By using a
16  GPIO expander it is possible to use the driver with one of the popular I2C
17  expander boards based on the PCF8574 available for these displays. For
18  an example see below.
19
20properties:
21  compatible:
22    const: hit,hd44780
23
24  data-gpios:
25    description:
26      GPIO pins connected to the data signal lines DB0-DB7 (8-bit mode) or
27      DB4-DB7 (4-bit mode) of the LCD Controller's bus interface.
28    oneOf:
29      - maxItems: 4
30      - maxItems: 8
31
32  enable-gpios:
33    description:
34      GPIO pin connected to the "E" (Enable) signal line of the LCD
35      Controller's bus interface.
36    maxItems: 1
37
38  rs-gpios:
39    description:
40      GPIO pin connected to the "RS" (Register Select) signal line of the LCD
41      Controller's bus interface.
42    maxItems: 1
43
44  rw-gpios:
45    description:
46      GPIO pin connected to the "RW" (Read/Write) signal line of the LCD
47      Controller's bus interface.
48    maxItems: 1
49
50  backlight-gpios:
51    description: GPIO pin used for enabling the LCD's backlight.
52    maxItems: 1
53
54  display-height-chars:
55    description: Height of the display, in character cells,
56    $ref: /schemas/types.yaml#/definitions/uint32
57    minimum: 1
58    maximum: 4
59
60  display-width-chars:
61    description: Width of the display, in character cells.
62    $ref: /schemas/types.yaml#/definitions/uint32
63    minimum: 1
64    maximum: 64
65
66  internal-buffer-width:
67    description:
68      Internal buffer width (default is 40 for displays with 1 or 2 lines, and
69      display-width-chars for displays with more than 2 lines).
70    $ref: /schemas/types.yaml#/definitions/uint32
71    minimum: 1
72    maximum: 64
73
74required:
75  - compatible
76  - data-gpios
77  - enable-gpios
78  - rs-gpios
79  - display-height-chars
80  - display-width-chars
81
82additionalProperties: false
83
84examples:
85  - |
86    #include <dt-bindings/gpio/gpio.h>
87    display-controller {
88        compatible = "hit,hd44780";
89
90        data-gpios = <&hc595 0 GPIO_ACTIVE_HIGH>,
91                     <&hc595 1 GPIO_ACTIVE_HIGH>,
92                     <&hc595 2 GPIO_ACTIVE_HIGH>,
93                     <&hc595 3 GPIO_ACTIVE_HIGH>;
94        enable-gpios = <&hc595 4 GPIO_ACTIVE_HIGH>;
95        rs-gpios = <&hc595 5 GPIO_ACTIVE_HIGH>;
96
97        display-height-chars = <2>;
98        display-width-chars = <16>;
99    };
100
101  - |
102    #include <dt-bindings/gpio/gpio.h>
103    i2c {
104        #address-cells = <1>;
105        #size-cells = <0>;
106
107        pcf8574: gpio-expander@27 {
108            compatible = "nxp,pcf8574";
109            reg = <0x27>;
110            gpio-controller;
111            #gpio-cells = <2>;
112        };
113    };
114
115    display-controller {
116        compatible = "hit,hd44780";
117        display-height-chars = <2>;
118        display-width-chars = <16>;
119        data-gpios = <&pcf8574 4 GPIO_ACTIVE_HIGH>,
120                     <&pcf8574 5 GPIO_ACTIVE_HIGH>,
121                     <&pcf8574 6 GPIO_ACTIVE_HIGH>,
122                     <&pcf8574 7 GPIO_ACTIVE_HIGH>;
123        enable-gpios = <&pcf8574 2 GPIO_ACTIVE_HIGH>;
124        rs-gpios = <&pcf8574 0 GPIO_ACTIVE_HIGH>;
125        rw-gpios = <&pcf8574 1 GPIO_ACTIVE_HIGH>;
126        backlight-gpios = <&pcf8574 3 GPIO_ACTIVE_HIGH>;
127    };
128