[Coco] POSSIBLE Solutions For RS-232 Problem

[Allen Huffman]

> On Feb 22, 2018, at 9:56 AM, Joe Schutts via Coco <coco at maltedmedia.com> wrote:
> 
> I recently came across an article from someone (I don't know who) about a POSSIBLE FIX (OR PATCH) for the CoCo RS-232 Pack and I thought I'd share (the article) with everyone who's been trying to FIX this problem in that it might finally happen.
> Anyway here it is, I hope this helps...

Wow, Joe. This is good stuff. And it better (re)explains to me the SACIA hacks. I had done this waybackwhen, and this leads me to wonder if we could *ever* use an RS-232 pak without some kind of mod.

I have also, since, found out that Commodore inverted it’s RS-232 signals... HIGH and LOW meant the opposite. The Zimodem firmware therefore is sending and expecting the reverse. A standard RS-232 device the turns on the “you can send me data now” signal is read on the Zimodem side as “do not send me data.” When Zimodem sends a carrier detect, it sends the opposite so it’s read as “no carrier” on the other side.

There are simple ATSxx commands to change this functionality, so last night I was able to correct wire up the ESP8266 module and change settings and make it work.

However, I had to force DCD on in Zimodem and one other signal to make the RS-232 Pak happy.

I’ll review this writeup and compile all the results to a blog post, shortly.

		— A