So I got my Parallax USR2SER in yesterday. Man is this thing tiny!! About the same width of my finger, and about 1/3 the length! And its mostly surface mount stuff…..
It works like a charm. Easy installation, I was just using hyperterminal which will accept up to 921600 baud, so that’s what I was trying. I was bit-banging a port with the “pauseus” SX/B command just for some quick tests. It’s LSB just like RS-232, but not inverted, and is 0-5v. Its ASYNC and so you need start/stop bits which are exactly the same length as a data bit. The start/stop is also inverted from 232 too, which I guessed. The normal idle condition is HIGH, and so the start bit is low, 0’s are low, 1’s are high, and stop bis are high just like the idle condition. So you have to remember to separate your bytes by an extra idle period, but that’s easy enough.
The green RX activity LED on the unit stays on solid when xmitting at 921,600.
I really like the nature of USB and serial vs using a parallel port. I can’t quite explain it, but it feels more solid and reliable to me. I guess the ASYNC nature of it means there are no goofy clocking issues to deal with. And although I’m not sure how windows handles this at any level, but I’ll bet there’s some buffering going on someplace to ensure data doesn’t get dropped.
I haven’t tried receiving the data through my own windows software, but that’s the next step.