Well, the DTR/DSR loopback became moot. Both of the shifters that I had that supported DSR/DTR failed. I couldn't get them to work at all (even without the DTR/DSR settings). I think I messed them up a while back.
But it seems that 1200 BPS will work off the internal Mega serial ports with the known good shifter that I have. So this project is a success. Thanks to all of you who helped me out. I appreciate it. My project is documented on github (https://github.com/rlauzon/MemoSaver) if you want to see what I did. It was a simple project, but it helped me pass the time until I start my new job on Monday. On Wed, Nov 29, 2017 at 6:02 PM, John R. Hogerhuis <jho...@pobox.com> wrote: > > > On Wed, Nov 29, 2017 at 2:53 PM, Ron Lauzon <rlau...@gmail.com> wrote: >> >> >> I broke out the RS-232 shifters that supports DSR/DTR and set them up >> to loopback on the RS-232 side, but I couldn't get them to work. >> I have a couple of things I need to check, but I think those shifters >> simply don't work. >> > > Hello Ron, > > Some confusion here, at least as to what I'm suggesting. > > DSR / DTR loopback is completely on the Model 100 side of the cabling. Has > nothing to do with the level shifter or the Arduino. > > Imagine on the M100's DB25, directly wiring the M100's DTR pin to M100's DSR > pin. That's it. So if you have a custom cable you're just shorting one pin > to another at the DB25 end. No wire in the cable is involved, just at the > connector. > > The old Club100 "comp-link" cable did this. It completely defeats the M100's > DSR check, since whenever serial port is activated, the DTR is kept > asserted. > > -- John. -- Ron Lauzon - rlauzon at acm dot org Homepage: http://webpages.charter.net/rlauzon/ Weblog: http://ronsapartment.blogspot.com/ TRS-80 Pocket Computer 2 - TRS-80 Pocket Computer 4 - TRS-80 Model 100/102 Some people like to work on old cars. But old computers are cheaper and don't require a big garage.
