I've never seen even one complaint that MAX3232 connected to a DE9 (more or less standard) 9-pin D-connectors don't work. I have, as you suggest, seen a number of complaints about the USB-to-whatever adapters now widely marketed.

From what I've concluded, particularly in light of a remark made not to long ago by Andy, that most of the USB-to-parallel port adapters work, and I'd guess that the vendors of USB-to-RS232 adapters have worked out the bugs, too. I suspect some of the bugs have simply been "ruled out" by statements on the order of, "this adapter will not do the following ..."

I know that at least one such USB-to-Parallel adapter does not support EPP mode or even bidirectional (PS/2) mode. That's enough to keep me using "real" parallel ports. Of course, that means I have to continue using my 12-year-old notebook, since it has the "real" serial and parallel ports on it, while the new ones don't.

Those adapters to which I referred are just a little PCB with that serial port connector, a fully implemented MAX3232A, and a connector through which you can input your low-voltage (3 Volt to 5 volt) serial output from the MCU.

If your MCU UART works, so do these adapter modules. All they do is shift the levels to RS232 levels. They do nothing to the signaling protocol.

EBay is also full of RF adapters that can be substituted for one of these adapter modules. Some of them, notably the ones with the NORDIC chip

http://www.ebay.com/itm/Leate...3f180ef291

or several at 315 MHz or 433 MHz that cost less than $2US. I've generally found the Nordic versions for under $2US for a pair, and the lower frequency ones for about the same price for the same functions, though they require two modules, which allows you to separate them on the board.

Signaling protocol is the end-user's problem.

RE