VFD/LCD piggybacking to grab data for remote app or emulator?

I have a device with a Noritake CU16025ECPB-W6J 2x16 VFD display. I want to piggyback an Arduino off the VFD pins to capture and parse the display data for use in a remote control app and possibly an LCD emulator. This particular Noritake uses the familiar E, R/W. RS and D0-D7 interface. I did a search and found similar projects but none have reported success, such as

The challenge is the Arduino can't grab data off the display pins fast enough. My approach so far is, first see what data is being written to the display, to see whether it's operating in 8 or 4 bit mode etc. then develop from there. Triggering an interrupt on the E pin falling edge to to read RS and D0-D7, 99.99% of the time I'm seeing RS=0 (instruction) and D0-D7 is always either 80, CF or FF. By fiddling with the code I occasionally see RS=1, but nothing that corresponds to what's on the display. I don't care about reads from the display, or at least I don't think I care, so I'm only trying to capture instruction and data writes.

One of the approaches suggested in the above threads is to latch the display pin data long enough for the Arduino to read it. I googled around and it looks like a 74HC573 might work. This chip has eight inputs and outputs, an LE pin that latches the inputs, and an OE pin to switch the outputs between tri-state and the output of the latch. I am thinking the simplest implementation would be leave OE low (output enable) and use E to trigger both LE (latch enable) and the Arduino interrupt. This would freeze the display data presented to the Arduino until E rises again so it can be successfully read.

Any thoughts or suggestions on how to approach this project will be greatly appreciated. Thanks for reading, Russ

It's normally faster to poll a pin than use an interrupt.

Fast write pulses are hard to poll. at least pin change flags should be used, and port reads.

But a much faster processor, or external hardware, may be required to catch all writes to the display.

How fast do you want to sample and why?

What is the application?

Thanks.. Tom.... :slight_smile:

Buy a logic analyser.