Intercept LCD Writes

Started by john_hightower September 7, 2007
I am trying to capture data from a handheld device that has a
proprietary processor that is writing to a Hitachi HD61603 LCD driver.
I need to read the bit streams from 4 data lines to determine what is
written to the display. Each bit stream contains 16 bits of data plus
start and stop bits and takes just under 3 milliseconds. I found the
protocol at http://www.pacificdisplay.com/ics_app%
20notes/hitachi/HD61602-61603.pdf.

Is there a way to read this into a bx-24? The InputCapture function
will only allow me to monitor one line.
> ... InputCapture function will only allow me to monitor one line.

If you need to essentially tap real time display data, you're right,
InputCapture can't do more than one line concurrently so it wouldn't be
useful. If this is a bench experiment to reverse-engineer something,
though, you could use InputCapture to do the same test four times, once
for each line. But...

> ... Each bit stream contains 16 bits of data plus start and stop bits
and takes just under 3 milliseconds.

That's an average of ~ 5.3kHz. I think that's too fast to sample five
input pins (4x data, + WE clock) simultaneously (by reading
register.PINC for pins 5-12, for example) on the BX-24p, but not by
much. Certainly a small AVR or PIC could do that quickly enough, and
you can find a another BX-24-like product that might do it, too. You
could also build a hardware interface, one that shifts 4x4 bits in,
clocked by the display's WE, and which shifts 1x16 out to the processor,
using ShiftIn or SPI.
Tom