Get a PC and 8-bit computer to talk using XBees

Hello everybody,

I’m fairly new to the forum, been here browsing for a few weeks looking for answers, or a problem similar to what I have. I’ve found a couple, but, it seems mine is different enough to not have the same answer.

What I’m trying to do is interface a PC to a Tandy Color Computer 3. The PC would act as a disk image server for the Tandy; basically, the PC is accessed using a floppy disk drive emulator software package called CoCoNet, and this cartridge, which has a 6551a and a custom version of the Tandy’s Disk Basic is pugged into the expansion port.

The cartridge uses a 6551a chip, and was intended to be used with an A7 Engineering EB301 bluetooth module - which is no longer in production - to provide wireless access to the PC. I thought the XBee would be a good replacement, since it can be used as a drop in serial cable replacement.

The PC’s XBee is connected to a Sparkfun USB Xbee Explorer, with the following settings:

ATID = 1111
ATMY = 10
ATDL = 11
ATBD = 7

The XBee connected to the Tandy serial pak is hooked up to and Adafruit XBee Adapter . I am only using the following pins, as they perfectly match that of the A7 EB301:

GND, CTS, 5v, Rx, Tx & RTS.

This XBee is configured the following way:

ATID = 1111
ATMY = 11
ATDL = 10
ATBD = 7

With these settings, I get successful ranges tests all day long.

Everything I’ve read says those settings should work for a transparent mode serial line. And it does, part way. There is a server software that runs on the PC, called CoCoNet server. When active, I can see the Color Computer connect successfully. I can mount disk images (the mounting process is initiated from the Tandy) all day long, and get the expected prompt on the PC app, and no error message on the Tandy.

The problem comes when I try to access the data on the mounted image - it always errors out. Using a very similar set up, it works all day long using the Tandy’s bit banger port.

I’m suspecting the there might be an issue with how the PC software sends the data which causes this problem, but, I have no real way to prove that right now. The software DOES require 1 stop bit for using the 6551 pak, and 2 stop bits for the bit banger connection. I’ve tried changing the stop bits to 2, but, I get no connection at all then.

I know this isn’t a typical problem that 99.99999999999% of you would encounter, but, if anyone has any thoughts on what the problem could be, I’d appreciate some ideas.