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| Reverse Engineering an LCD |
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| MotoDan:
I've got a custom segment style LCD that I need to have made by another vendor and do not have the original documentation for. I have already done some initial RE and know the bias type (1/4 multiplexed) and have a partial pinout for the 4 common pins. What I need next is the segment pin map (schematic) so that I can finish the drawings needed to have the display made. My first thought was to apply a voltage to each common pin and walk through the remaining segment pins, noting which segments light up. There must be more to this step than I anticipated because I am not having any luck getting any of the segments to turn on. I've tried common voltages ranging from 0 to 5V. Another thought was to de-laminate the two glass sections to see if I could generate the schematic that way. I only have one display and don't want to ruin my chance of mapping this one. The display is driven by a PIC with a built-in LCD controller. I don't have the source code for the PIC so can't go about it that way. The product that uses this display has been in production for years and there is no chance of altering the LCD's pinout at this point or changing the firmware. Looking for suggestions on getting this display's pinout defined out without having to pay the manufacture to do it. Thanks! |
| EEVblog:
--- Quote from: MotoDan on March 20, 2019, 02:49:15 am ---Another thought was to de-laminate the two glass sections to see if I could generate the schematic that way. I only have one display and don't want to ruin my chance of mapping this one. --- End quote --- Can you get the at the right angle under bright light and see the traces? |
| MotoDan:
Hi Dave, No, I've tried, but can't quite see the traces regardless of the angle, lighting, etc. |
| IconicPCB:
The display as You know works as segments over a common electrode field. Make up an oscilator ( cmos schmidt trigger inverter gate) pass it through a couple of inverter gates (connected in series) and use the two buffered outputs to drive plane and segment pins. You are now ready to seek out the segment pin combinations. Egg me if I am teaching a granny how to suck eggs. You can also egg me if you dont like my politics...its OK. |
| Gyro:
--- Quote from: MotoDan on March 20, 2019, 03:52:22 am ---Hi Dave, No, I've tried, but can't quite see the traces regardless of the angle, lighting, etc. --- End quote --- Strangely, breathing heavily on it (light condensation) sometimes helps. |
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