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PostPosted: Tue Mar 30, 2010 14:27 
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Joined: Tue Mar 30, 2010 13:35
Posts: 1
Hi

I got a couple of these palm pilot pda type monochrome lcd screens from excesssolutions.com for $5 each. They look like palm pilot pda lcds, but the icons on the 4 corners of the "graffiti" input area are slightly different.

20 pin connector. 4 pins go to the touchscreen interface. Onboard HV826 EL backlight driver IC. Also appears to have onboard contrast voltage supply circuit, there is a testpad with a 15V - 21.5V when the panel is powered.

Have managed to figure out the following signals on the pinout. I am powering with a 3.3V supply and logic.

20 d3
19 d2
18 d1
17 d0
16
15 contrast ? pwm control ? (0 =>15V on testpad, 3.3V => 21.5V)
14 enable
13 gnd
12 Vcc
11
10
9 hsync (lp)
8 dclk (cp)
7 gnd
6
5 bklight
4 touchscreen
3 touchscreen
2 touchscreen
1 touchscreen

Olimex has a schematic and demo code for their palm pilot pda lcd picvue PC0919WE07 based evaluation board.

I used their source code as a template, driving the signals from a timer driven interrupt routine.

Experimenting with the pin combinations, I am now reasonably sure of the databus, hsync and dclk, because I can drive 0x8 on the 4bit databus and see that pixels 1, 5, 9... on every line are black, driving 0x1 makes pixels 4, 8, 12, ... black on every line.

But the screen fades immediately after the first frame draw (which has very good contrast, btw). So I am unsure about the Vsync (flm) signal, not sure if a bias signal is required, the timing, and possibly existence of other control/power pins that i am not driving correctly.

The olimex schematic for the PC0919WE07 (and their source code) did not show a bias pin. But on their 20-pin interface the EL driver and contrast voltage supply also appear to be external to the lcd panel, so this one could be substantially different.

Any pointers would be much appreciated - I could really make use of these lcds !!


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