Wiring Up The Display

This driver ICs need a ladder of voltages to correctly bias the display. The driver datasheet contains irritatingly incomplete information on this. Basically it is wired so that V0 > V12C > V12 > V43 > V43C >V5. The voltages should be evenly spaced except for the difference between V12 and V43 which will determine the display contrast and dictate the required V0 level. I setup my display so that the difference between V12 and V43 was 10 times that of the other differences and needed about 19V at V0. I probably could have gotten away with a lower voltage without any perceivable contrast difference. This display is very low power and did not require buffering. The circuit must ensure that VDD goes live before V0, otherwise damage to the display could result. I once killed an unrelated Hantronix display by blowing that requirement off.

I used a PIC32 mounted to a homemade adapter card and a breadboard to do my testing. I also made a breakout for the FPC connector of the display. Ready made FPC breakouts can be purchased from various places like Fry’s Electronics in the US (Schmartboard), or the Newhaven Display website. See the files section for a hook-up schematic.

My breadboard setup. Backlight is on.

Writing the Firmware

Controlling the LCD is actually fairly simple and straightforward. You would never know that, however, from reading a Driver IC datasheet. Not only that, all of the driver IC datasheets have apparently copied each other. Thus, viewing a different data sheet nets you no new information. This is basically how it works:

1. Each byte of data is clocked in 4 bits at a time, with the high nibble coming first. Data is latched at the falling edge of XCK.
2. When 30 bytes of data have been clocked in (i.e. XCK has been pulsed 60 times) for 240 columns, you are done with a row. You now pulse LP and do #1 over again.
3. When you have completed all 160 lines, pull EIO2 (FLM) high, pulse LP, then drop EIO2.
4. Invert F/R (not pulse!). This is important because a continuous DC bias will ruin the display.
5. Start over.

With the PIC32 running at 80Mhz, and compiler optimization turned on, the LCD controller code consumer about 7% of the available processing time. I included a idle time checking utility in the sample firmware.

PIC32 idle time while controlling LCD.

Setting Up Touch and Putting it together

I am not going to go into detail about how resistive touch works because there are plenty of resources on this. I did write a driver using the PIC32 ADC and you are welcome to examine it. I have uploaded a video demo of the display in action.

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