HP LaserJet 4000 front panel

Here is front panel from HP LaserJet 4000 printer. It has 2×16 LCD ( Hitachi HD66710 controller ) , 3 LED indicators and 9 push buttons

On the back PCB there are 20 pin LCD connector (J2) and 10 pin connector (J1). LCD module also has 20 pin connector.

 
Connector on LCD , J1 and J2 pinout:

 

Description	10 pin connector (J1)	20 pin connector (Connector on LCD and J2)
GND	2,4,6,10	19
3.3V	1	18
5V (backlight)	9	20
SEL	3	14
CLK (SCLK)	5	15
DIN (MOSI)	7	17
DOUT (MISO)	8	16

From programmers side of view this panel is similar to HP LaserJet 4500 panel:

https://kbiva.wordpress.com/2012/12/30/hp-laserjet-4500-front-panel/

Some differences from  HP LaserJet 4500 panel:

• It has blinking cursor.
• Lower SPI speed (must use SPI_BaudRatePrescaler_256; SPI speed is 281.25kHz ).
• SPI clock phase must be SPI_CPHA_1Edge.

Here is video showing demo :

Left button press toggles led. Right button press turns led on and turns led off when released. Select button toggles all three leds. Small red button turns off backlight, and big green button turns the backlight on. On the screen there is a counter that is incremented every millisecond and a “heart” that flashes every second.