I'm wondering if something like this is possible... I've got a device that has an onboard RFID reader, and it sends the output of the tag via serial to a microcontroller to "do it's thing" with. I know the output is serial, because the datasheet of the RFID chip actually has the pins labelled as "serial in", "serial out", and "serial clock". It's one of those stupid painted boards, so I can't completely follow the traces to see where they're going, but I'm thinking I shouldn't need to.
I tested this in theory by using a desktop PC connected to a Cisco router via RS-232 console cable. I spliced into the cable, and attached the "receive" line from a second cable (connected to my laptop) to the "transmit" line from the router. If I open up HyperTerm on both the desktop and laptop, and then power on the router, sure enough I can see the router's output in both terminal windows. So, in theory, this is doable.
Now, I don't know what levels or anything the transmission is happening at on these chips. I've tried attaching the same cable mentioned above, as well as an FTDI TTL-232R (5V) cable to the "serial out" pin on this chip, and then brought the RFID chip into antenna range. The biggest pitfall seems to be that I have no idea what speed I should be setting HyperTerm at... on the Cisco router, I already know it's 9600/8/N/1, but how would I determine it in this other scenario? I've got the full data sheets for both chips, but I'm kind of at a loss.
I have a known-value transponder, but no matter what baud rate, stop bits, etc. I choose, and no matter which of the two cables I try above, I get nothing but garbage in my HyperTerm window.
Any help would be GREATLY appreciated!