Looks like the project is also using the software serial option. Wondering if that is causing the problems? As some encouragement in the past I have used the software serial port option on an Arduino Pro Mini at 9600bps but that was not for connecting to the T102. The 9600bps was the limit due to the processing requirements on the Arduino for the device it was managing. We could actually run it faster but then could do no other processing. This project did not have any control signals to worry about fortunately!!
I am running an Atmega 644PA on the serial port of a T102 at 19200 without any issues but that uses the ³real² serial port. The Mega is only running at 8MHz and easily keeps up with the T102 doing uploads or downloads via Term. Spends most of its time idle waiting for the T102, even including writing/reading to/from the SD Card. It can support XON/XOFF but it never uses it at 19200. This design does loop back the control signals on the RS232 connector though. I will be switching to an ESP8266 as soon as the new PCBs arrive later this month, it runs a bit faster :) My Xmas projectŠ On 1/12/17, 5:00 PM, "M100 on behalf of Ron Lauzon" <[email protected] on behalf of [email protected]> wrote: >This project ><https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fzx81key >boardadventure.blogspot.com%2F2017%2F08%2Fmodel-100-micro-sd-card-reader-m >ytesed.html&data=02%7C01%7Cb4me100%40hotmail.com%7Cfecc57892f4e4eace64a08d >5392009dc%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636477732114008721& >sdata=vT8OS3jj2QxhFPSMetJGHKhT87FjB%2Bev0Z5EsYNo5wQ%3D&reserved=0> >gave me the idea to try my project. He is using 1200 BPS as well. >But, strangely, he's using 7 bits and ignoring parity, as well as >turning off XON/XOFF. > >I'm in control of what the Arduino sends, so I know it's not sending >an XOFF. Now that doesn't mean that something else is happening and >an XOFF is getting sent to my T102. >I'm running on the assumption that the Arduino, being much newer >hardware, should have no trouble keeping up with the T102. I think >that's a correct assumption, but it's still an assumption. > >If I spent the resources to get an RS-232 monitor, I might be able to >see which end is having the issue, but it's not worth it to me right >now. > >On Thu, Nov 30, 2017 at 5:30 PM, Mike Stein <[email protected]> wrote: >> Sounds nice! >> >> Nothing wrong with using a 'shifter' and I'm just picking a nit, but >>the issue with interfacing RS232 to TTL in this case is not so much the >>voltage but the polarity. The ModelT outputs +5V to -5V and some >>TTL-type inputs don't like a negative voltage even if it's current >>limited as it is in the Model T's; it's recommended to clamp the -5V at >>0V somehow, which your shifter takes care of. Receiving a TTL-level >>signal on the ModelT will usually work, but a bipolar RS232 is somewhat >>more reliable. >> >> Still odd that you can't go above 1200bd; have you tried disabling >>XON/XOFF (with the loopbacks connected) in case the Arduino is sending >>an XOFF but never an XON? Since nothing changes on the T102 except the >>speed it would suggest that the other end can't keep up for some reason >>and a buffer is filling up somewhere, unless there's an issue with >>parity or framing. > > >-- >Ron Lauzon - rlauzon at acm dot org > Homepage: >https://nam01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwebpages. >charter.net%2Frlauzon%2F&data=02%7C01%7Cb4me100%40hotmail.com%7Cfecc57892f >4e4eace64a08d5392009dc%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636477 >732114008721&sdata=wEewAmAjDMZ%2BQ5YJ8HyNZQn24pe%2FOME4C3dEn0fOkmg%3D&rese >rved=0 > Weblog: >https://nam01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fronsapart >ment.blogspot.com%2F&data=02%7C01%7Cb4me100%40hotmail.com%7Cfecc57892f4e4e >ace64a08d5392009dc%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C6364777321 >14008721&sdata=Bx4u15tOCtvOZ%2BdVPQwwarWy%2BOSGEF%2FdRm76ZO8b9KA%3D&reserv >ed=0 > >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.
