Hitachi LCD Displays

Source: http://www.josepino.com/?hitachi_displays   Tags: electronics circuits howto

LCD display Hitachi compatibles (HD44780) are the standard in many LCD models. Some models are 8 caracteres by 1 line, 8 x 2 lines, 16 x 1 line, 16 x 2 lines, 20 x 2 Lines, 24 x 2 lines, 20 x 4 lines and 40 x 2 lines. There is more especifications, but here is only a few that I have.

The Pinout configuration on these display are:
Taken from http://www.josepino.com

That is the standard pinout information, however, may not match with some LCD displays Hitachi compatible. Some old laser printers (like HP IIP & IIIP) have an LCD compatible but pines 1 & 2 are inverted. These displays are labeled as SH7-9230.

Some LCD Hitachi compatibles I have. The last one was removed from an old HP Laserjet IIP.

Connectors and parts maybe are different, but the controller is a standard Hitachi. Models in the picture are: (From top to botton) HD44780A00, ED242X0TEY, HC16102JC y SH7-9230

Here is the character set for some of the Hitachi displays (specially the SH7-9230)

Compared with 7-segment LED displays, LCD displays require less voltage (5 volts DC), and doesn't need a frecuente "refresh" to avoid flickering, but is controlled by commands.

Interfasing. Sending commands or data to display. (8 bits mode)

Sending commands procedure:

1. Connect to ground (-) R/W. (Set to WRITE)
2. Connect to ground (-) 'RS' (Set to command mode)
3. Enable 'E' (+)
4. Send data byte (8 bits, D0 to D7)
5. Disable 'E' (-)
6. Wait at least 40us before send next command or data.

Sending data procedure.

1. Connect to GND 'R/W' (Set to write)
2. Connect to Positive 'RS' (Set to Data mode)
3. Enable 'E' (+)
4. Send data byte (8 bits, D0 to D7)
5. Disable 'E' (-)
6. Wait at least 40us before sending next data or command.

Note the difference is the pin 'RS'.

Here is an example of timing for the LCD display. (4 bits)

(SOURCE: HD44780 datasheet)

HD44780 Instruction set & bit names:

Each code means a BIT. For example, to turn off the curson, set 'D' as 0 (See the command "Display ON/OFF Control")

NOTE: Waiting time varies, sometimes is necessary to wait just 50 nanoseconds. However, I recommend to wait up to one milisecond to avoid problems with some displays. The HD44780 Datasheet have more commands, here is only a few of them, just the basic to control the LCD Display.

LCD Initialization procedure.

According to the Hitachi datasheet, here are the necessary steps to initialize the LCD before display any data: (Asterisc means "Don't Care")

1. Power On.
2. Wait 40 ms until power rises.
3. Write command 0 0 1 1 * * * * (Function Set. DL=1, 8 Bits)
4. Wait 5 ms
5. Write command 0 0 1 1 * * * *
6. Wait 1 ms.
7. Write command 0 0 1 1 * * * *
8. Wait 1 ms.
9. Write command 0 0 1 1 N F * * (Function Set. Set on N & F according to display)
10. Wait 1 ms.
11. Write command 0 0 0 0 1 0 0 0
12. Wait 1 ms.
13. Write command 0 0 0 0 0 0 0 1 (Display Clear)
14. Wait 1 ms.
15. Write command 0 0 0 0 0 1 1 0 (Entry Mode Set)
16. Wait 1 ms.

Now, the LCD is ready to display data.

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