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57 lines
2.4 KiB
Markdown
57 lines
2.4 KiB
Markdown
# Hitachi HD44780 Package
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## Overview
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The Hitachi HD44780 is an LCD driver chip. It's used in a variety of text LCD
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displays. The datasheet is available here:
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https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
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Generally, there are three kinds of displays that use this chip.
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1. A raw display. This is a board with a row of pin connectors at the top. It's
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made for interfacing directly to GPIO pins. This is the most complicated method
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of using the LCD because you have to wire a minimum of 6 GPIO pins (4 data, 1
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reset, 1 enable) and 2 power pins to make it work.
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There are also complex initialization routines that have to be performed. This
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is further complicated by having specific initialization calls depending upon
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whether the device is connected to 4 data lines, or 8 data lines.
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2. A backpack display. With this type of LCD display, an I2C, serial, or SPI
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interface is provided. This type of display is easier because there are fewer
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pins, but the complex intialization remains. Examples of backpack interfaces
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include The Adafruit I2C/SPI backpack (MCP23008/74HC595D), the generic
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LCDXXXX/PCF8547T backpack, etc.
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3. The third and final variety is the "Intelligent" display. These displays have
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a micro-controller that is connected to the LCD chip. Typically these intelligent
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displays support multiple I/O methods and the micro-controller handles the
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LCD initialization/communication.
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Examples of this kind of display would be the SparkFun SerLCD display, the
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MatrixOrbital LK2047T, the AdaFruit USB+Serial Backpack etc.
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## Interfacing Notes
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The driver package is designed to use the gpio.Group interface. This allows
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the LCD driver to be agnostic about the physical connection between the display
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and the host device. Any host/expander that supports the GPIO group can be used
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to easily drive the LCD display.
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## Hardware Notes
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DO NOT attempt to source VCC for the unit backlight, or sink VCC to ground.
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The backlight draws ~250ma of current which exceeds the current capability
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of GPIO pins. It will permanently damage your device. If you would like to
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control the backlight, connect a GPIO pin through a 1K Ohm resistor to a
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transistor (2N2222 or equivalent).
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## Troubleshooting
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If nothing displays at all, check the contrast. Adjust the contrast control
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until the 5x7 dot grid on the display is visible.
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If the text is garbled, verify the gpio.Group is configured and the IO Pins
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are connected to the right pins of the LCD display.
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