LCD Screen Output (HP-49, 110+)

[Martin Hepperle]

(12-05-2014 11:22 PM)BruceH Wrote:  It doesn't have to be any faster than the screen refresh rate of the built-in LCD - which isn't the fastest thing in the world, for the 39/49 at least. An RPi would do the job.

That's how I understand how the system works:
The screen refresh rate is about 50Hz, but the pixels are sent out as several serial streams - one for each quadrant of the screen (Portable: dot clock <= 1.25 MHz). They would have to be captured, combined and stored in a RAM and then, after a frame is complete, one would have to output the frame according to the external display needs, e.g. scan line by scan line. Therefore I think one has to capture the data at a relatively high rate.
In case of the HP-49G the screen is split into two halves, so that only two pixel streams have to be captured. It would be a nice project to hook up modern TFT screens to these machines.

Martin