Project thoughts about CP/M board... - Page 1
Forum section: electronics / projects

author: alank2
author_rank: Super Contributor
timestamp: August 29, 2016, 12:38:09 am
content: Hi Everyone,I've been playing around with Grant Searle's CP/M on FPGA project:http://searle.hostei.com/grant/Multicomp/index.html...and learning / changing the VHDL at the same time. Right now it is a mess of a EP2C5T144C8N development board and a breadboard with sram, serial, ps/2, and vga connectors on it.I was thinking about making a single board that has everything on it, or perhaps a plug on board that plug onto the development board to add the sram and ports.Then I was thinking what about an integrated video/keyboard? I know it wouldn't be the best keyboard, but I really love standalone handheld gadgets and I've already done a smaller keyboard for the microenigma I built:So my first question is instead of VGA output which is what Grants project has, would it be fairly easy to modify the VGA output into RGB output for a 4.3" TFT ? They seem to need to be refreshed just like VGA does, but perhaps with different timing.I would have to figure out which keys are necessary on a CP/M keyboard to make sure my keyboard included them. Obviously control, shift, enter, capslock, but I suppose I'd have to look at several popular CP/M systems and see what keys they supported.I've already modified the project to have a concurrent vga/ps2 with serial so it outputs to both and accepts input from both.I would need to work on the full support of ansi/vt100 sequences which I wonder if would be better implemented in the CP/M bios instead of vhdl, but that would be something else to think about.It, like most projects, seems like a lot of work, but I wonder if it would be cool/worthwhile in the end. Would a single board with a tactile button keyboard and 4.3" TFT display be something cool to work on/play with? You could always connect it to a larger terminal over serial. Thinking out loud here!What do you guys think? Any other thoughts or ideas?

author: rstofer
author_rank: Super Contributor
timestamp: August 30, 2016, 08:14:17 pm
content: Quote from: alank2 on August 29, 2016, 12:38:09 amVGA is a lot like RGB but it adds HSYNC and VSYNC. I would suspect that almost any monitor is going to need similar signals. Just change the VGA VHDL to match the required timing. Should be pretty easy.QuoteI don't recall that any of the special keys (F1..F12, Media, Alt, etc) were ever used. You could accept them and just return a default character like '.'. I don't recall what I did when I built a CP/M system several years ago.QuoteI did it in BIOS because it is easy but the problem is, you want to limit the size of BIOS so you can maximize program space. BIOS doesn't care about which characters it sends to the display so why not let the display handle it. That's the way it worked in the real world when you plugged in a VT-100.QuoteSure, why not? I would look at the 7" display at Adafruit. There site is a mess right now so I can't link the item.A better Z80 project is PacMan:http://arcade.gadgetfactory.net/index.php?n=Main.PacManHelpI have that running on a Spartan 3E board but I have had a lot of pushback re: building yet another arcade machine. but we have a bigger house now. Maybe the war department will approve the project.