I looked for an Arduino library that would talk to this chip-set, but failed to find one.

I based my library module for this on a standard Arduino library for the Hitachi HD44780 chip, LiquidCrystal.cpp. The programs included here are HelloWorld.ino, LiquidCrystal_ks0073.cpp and LiquidCrystal_ks0073.h.

The command set is compatible with the Hitachi HD44780 with extensions.

The controller is mounted on a PCB joined to the LCD glass via a PCB flex cable, and the LCD module has a 10 pin, 1mm pitch, PCB flex cable to connect to a suitable socket. The displays are a two lines of twentyfour, 5 by 8 pixel, characters.

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The great advantage of these serial SPI LCD modules is the simplicity of the Arduino interface. There are four signal lines SID (data to the display), SOD (responses from the display), SCLK (clock), and CS (select). Plus power (+5V) and ground (the module should also work from a 3.3V supply).

The controller chip is capable of parallel and serial interfacing, but on this module it is hardwired for serial connection. It uses its own variation of a SPI protocol where data and commands are prefixed by a control byte that specifies what the following bytes are going to be - ie read or write data, or a command.

All data is sent least significant bit (LSB) first, on the rising edge of SCLK. The control byte consists of 5 successive “1”s followed by command/data register select (RS) and read/write (R/W) bits. So typically you assert CS and send a control byte indicating a command follows, then if there is data to be sent, send a control byte followed by a stream of data bytes terminated by releasing SS. Both commands and data are split into two nibbles and a prefix of four “0”s is added to each - so there will never be a command or data byte starting with four “1”s. ie to send 0x1F, you send 0x00 0x01 0x00 0x0F.

I used a minimum of 2uS for the clock cycle for SCLK and, as I was not checking the ready status of the chip, a delay of about 40uS between sending bytes to give sufficient time for the chip's internal processing.

There is a separate power line, VCI, to supply the voltage converter that sets the LCD contrast voltage, around 1.3V was typical.

The data pins can be any available Arduino pins.

As mentioned earlier the library is based on a standard Arduino HD44780 LCD library. Most hardware commands, including programmable characters, seem to be compatible with the HD44780, but I would need to do a lot of experimentation to find any extended commands.

The functions implemented are:

• begin(col,row)
  • Initializes the display, usually done once in a sketch's setup() routine.
• clear()
  • Clears the screen of all pixels and homes the cursor.
• home()
  • Sets the location for next data output (cursor location) to 0,0.
• display();
• noDisplay();
  • Turns the display on or off.
• blink();
• noBlink();
  • Turns the blinking cursor on or off.
• setCursor(col, row)
  • Set location for next character to be displayed.
• cursor()
  • Show cursor at location ready for next character.
• noCursor()
  • Turn off cursor display.
• scrollDisplayLeft()
  • Scroll current line one character to the left.
• scrollDisplayRight()
  • Scroll current line one character to the right.
• leftToRight()
  • Normal Western language display mode where words are written starting at the left of the display.
• rightToLeft()
  • Mode used for Japanese and other languages where characters are written starting at the right of the display.
• autoScroll()
  • Automatically scroll when the cursor (whether visible or not) reaches the far edge of the display.
• noAutoscroll()
  • Turns off autoscroll.
• createChar()
  • Programs one of the 4 user defined, 5×8 pixel characters.

The functions appear to be the same as for the HD44780 but have not been extensively tested for compatibility. There didn't seem to be any need for 4/8 bit interface selection. It is conceivable that the display controller chip might support 4/8 bit modes, but no account of this possibility is included in this driver. So initialisation is simplified.

When writing data to be displayed on the LCD screen it would be more efficient to assert SS, send a positioning command and then a stream of bytes, and de-assert SS when complete. But this driver has a, print.h library compatible, single-character output routine, 'write', which is used to output one character at a time, each preceded by a display-on command.

The original firmware sent an extra code, 0xf8, during startup. On an HD44780 chip this would just be a cursor positioning command (to set data cursor to location 0x78), but this would not be a displayable location, and no data is sent to be displayed. It appears that this may be a reset or other initialisation command.

I finally realised why I sometimes had trouble setting the programmable characters (only 4 available on these chips) - after setting a programmable character future writes also go to the programmable character CGRAM (corrupting it) until you deliberately switch back to the display ram. This is a problem from the original LiquidCrystal.h library - the solution here is that I just reset the cursor to the home location after programming characters.

LCD module displaying text output of helloworld.ino program

The programs (v1.00):

• helloworld.ino, sketch to test the LCD library
• liquidcrystal_ks0073.h, KS0073 SPI LCD library
• liquidcrystal_ks0073.cpp, KS0073 SPI LCD library

• Arduino LCD display drivers
• New LiquidCrystal
• Adafruit RGB LCD Shield-Library .

• METP0000, NEC µPD7225 based LCD display panel Arduino driver
• Canon MX300, Canon MX300/310 printer LCD display panel Arduino driver.
• NEC µPD7228 and μPD16434 LCD display panels Arduino driver
• SPI LCD, LCD display panel Arduino driver
• Toshiba T6A34 SPI, HD44780 compatible, LCD display panel Arduino driver

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