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Character LCD question

PostPosted: Aug Thu 20, 2009 12:54 am
by jrsharp
Hey everybody,

I just put together my Replica 1 TE and am anxious to get to work on some hardware hacking I have had in mind for it. I've really been interested in making my replica portable and had been brainstorming various ideas when I picked up the Back to the Garage book and was inspired while reading about the video section of the Replica 1... It mentioned using an ASCII LCD display directly as an alternative to the composite video output.

I've searched the forums here, but I haven't really found much evidence that people have done/are doing this with their Replicas... I happen to have a nice 40x4 character LCD display sitting here so I thought I'd give it a shot. This also plays nicely into my plans to make my replica portable, as the LCD should be significantly lighter on power than the 7" DVD LCD I had been planning on otherwise.

My idea is to actually build a simple video controller circuit/driver for the LCD using an Atmel AVR (ATMEGA16, likely) which can be responsible for mapping the 40x24 terminal to the 40x4 LCD by way of 6 "virtual" screens. The viewing of these screens could be controlled via pushbutton.

I suppose my question is, what is the best way to interface my AVR to the video output port of the 6821? Also, I would like to keep the normal video circuit as an option for displaying to an external monitor. Would it even be possible to output to both displays at once?

I've also considered modifying the firmware of the propeller chip to perform my LCD driving functions, but I'm not yet sure whether there are enough available I/O lines to manage that. Are schematics available for the TE edition?


PostPosted: Aug Sat 22, 2009 9:28 pm
by jrsharp
Dex, using the serial port is a good suggestion. I should've considered that myself. Of course, this is not a serial LCD module that I have, so I will still need to drive it using the AVR. This should work quite well, however, as the AVR has the UART and I can send the incoming byte directly out to the LCD.

I'll try to give this a shot tomorrow and see how it goes. Thanks again!