Hello all, Today I made myself a nice and simple serial cable - TX, RX and ground (I don't need anything else), and it works well when I connect 2 laptops to each other, running HyperTerminal. Unfortunately, HyperTerminal does not record serial data sent by 2 different evaluation boards (MCBSTR7/9), running Keil / ST sample code. What can be the cause of this? Can it be related to the type of wire I used? Any ideas are welcome!
Thanks in advance
Serial ports on computers are generally wired as DTE (Data Terminal Equipment) while the serial ports on evaluation boards are generally wired as DCE (Data Communications Equipment). What this means is that connecting DTE to DTE requires RX/TX swapping. However, DTE to DCE RX/TX is wired straight thru.
Jon
Why?
In general they are not DCEs - ie, they are not modems - so why are they wired as such?
Well they're DTEs even less than that. But they're typically meant to be connected to DTEs, so it's easier if their wiring is that of a DCE. For one thing, straight-through cabling is cheaper (just crimp a plug on a ribbon cable).
How so?
A DTE is a Data-circuit Terminating Equipment - ie it is the sink and/or source of the data being communicated.
That definition, if you think about it for a moment, means nothing at all. Both devices on the ends of a RS232 link "sink and/or source data".
The distinction between DTE and DCE has long since failed to apply to the usual circumstances RS232 links are used in, mostly because modems connected to a serial port have effectively ceased to exist.
I stand by my earlier statement: If there's a PC on one end of the RS232 link, that's clearly the DTE. So whatever else is on the other end gets to take the place of a DCE, no matter whether it's a modem or not.