The main board(which has switching power supplies, the ARM chip, printer head drivers, etc.will send the "HP" message to the front panel without any other connections other than the single 22-pin connector connecting to the front panel.
Ah. It wasn't clear whether you still had them connected or not.
22 pins is a common Active Matrix interconnect, I think. At least, the first AMLCD from a surplus store that I could find a datasheet for happens to have a 22pin connection as well. (
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13752 and
http://ens.ewi.tudelft.nl/~rene/acx705akm-7.pdf)
If it IS that sort of display, then your status is "mixed." On the one hand: pretty standard. OTOH, it's pretty much like driving a CRT with separated signals. No buffering, and you have to wiggle the signals at video frame rates (and frequently at weird voltages), over and over again. I've often wondered how much you can "cheat", since there isn't actually an electron beam striking phosphors. If you could get away with, say, cutting the clock by a factor of 10 and stiff have a legible display, it might be pretty easy. OTOH, hacking these things is popular, and I've never heard of anyone doing that, so it's probably not possible :-(
Some of these should be easy to check, even with just a voltmeter. Others might yield secrets to poking with an osilloscope.
1 MIC1
2 MIC2
3 VCC1 +3.8V power supply
4 VCC1 +3.8V power supply
5 GND
6 GND
7 R0 Red data input (LSB)
8 R1 Red data input
9 R2 Red data input (MSB)
10 G0 Green data input (LSB)
11 G1 Green data input
12 G2 Green data input (MSB)
13 B0 Blue data input (LSB)
14 B1 Blue data input
15 B2 Blue data input (MSB)
16 Hsync Hsync input
17 Vsync Vsync input
18 S/D Shut down
19 MCK Master clock (4.2MHz)
20 VCC2 +3.0V power supply
21 LED VDD
22 LED GND
Thanks a million sprites, westfw!
piob posted a reply earlier on this topic that had a link to someone successfully hacking a Canon TFT display that was apparently used in two legacy Canon printer models, but I was astounded by the amount of seemingly garbage code needed to get something to be displayed. Googled and Googled again, I have not found anybody who has succeeded in hacking an HP printer TFT display, but many have cracked the 16 x 2 LCD displays found on other HP lasers and inkjets.
Since your display pinout seems to use all 22 pins, it doesn't quite match, but I will have some time later this week to examine the 22 pin signals on my TFT to see how they match.
Its amazing, an approx 3.5 in 800x400 difficult to interface with RGB display at Farnell sells for about $100(incl. shipping cost)also requires buying tow special connectors and requires creating a RGB driver VRAM/control board setup to interface with, while a much bigger, better one that is just one part of a new powerful smartphone can be bought for under $70.
Makes my 3.-5 in HP TFT display at little more attractive to play with.
Its amazing, an approx 3.5 in 800x400 difficult to interface with RGB display at Farnell sells for about $100(incl. shipping cost)also requires buying tow special connectors and requires creating a RGB driver VRAM/control board setup to interface with, while a better one that is just one part of a new powerful smartphone can be bought for under $70.
Makes my 3.-5 in HP TFT display at little more attractive to play with.
Or even cheaper, see
here for a 3.2 in 648 x 360 phone LCD hack for approx. $10 with a bit of interfacing hardware.
Edit, fixed link.
Hey GMB42, the link you link does not link.
Thanks for the link that links, westfw,
I read all the info from the link and see that getting this Nokia display to dance to my tunes would be a tedious and expensive and time intensive, even hurry-up-and-wait task.
I would have to order the special connectors for the TFT available only from only Digikey USA, getting a PCB made in China would take about 6 weeks to arrive and the minimum order would require me to purchase several of the boards at some yet unknown price, and I would have to write a RGB driver to interface with my MCU. Even if I could find a source, the display requires meticulous soldering techniques of the TFT's very small footprint's easily damaged connector.
What would be the best buy-it-no hassle just use-it solution for anyone, that is, if it was available at a reasonable price would be a 3.5-in TFT display with a serial interface such as I2C or SPI and 3.3 or 5V interface..but while such displays do exist they are in the several hundred $$$$ range..expensive.
By that time I laid out the PCBs, ordered them and somehow manage to find the connector and solder it in and then write a driver, Hitler might be Mayor of New York.
Makes playing around with my HP TFT display maybe a little more like fun to play with.
This site has fantastically low prices and high quality TFT displays..has anyone tried dealing with this site?
http://www.buydisplay.com/