Can't reliably "Save Floppy" faster than 19200 baud on Unix

General discussions related to the Altair 8800 Clone

Can't reliably "Save Floppy" faster than 19200 baud on Unix

Postby unicode_rose » July 10th, 2018, 6:58 pm

I've got my new Altair Clone hooked up to my Mac with a serial-to-USB adapter, and I'm successfully talking to it via the Unix serial communications app minicom (installed via Homebrew). I've managed to successfully send disks to the Clone, setting minicom to 115200 8N1 and sending them via XMODEM (which required an additional install from Homebrew, lrzsz). However, receiving disks almost always fails with a slew of retry errors:

Code: Select all
rx: ready to receive foo.dsk
Retry 0: Got 04 sector header
Retry 1: Got 04 sector header
Retry 2: Got 04 sector header
Retry 3: Got 04 sector header
Retry 4: Got 04 sector header
Retry 5: Got 04 sector header
Retry 6: Got 04 sector header
Retry 7: Got 04 sector header
Retry 8: Got 04 sector header
Retry 9: Got 04 sector header
Blocks received: -1
rx: foo.dsk removed.

Transfer incomplete

The only way I've gotten receiving disks to work every time is to reduce the baud rate in both the Configuration Monitor and minicom to 19200 or 9600.

I also have an old Raspberry Pi (running its default Debian Linux) lying around, so I tested the same setup and ran into the same results. I've even tried bypassing minicom and redirecting sx/rx directly to /dev/ttyUSB0: once again, I can send with sx with no problems, but rx consistently fails on any speed higher than 19200 baud.

The only other thing I haven't been able to test is using the recommended Tera Term on Windows, because I have no Windows boxes in the house. Since Tera Term seems to be the terminal program of choice for most Clone users, I surmise that it's more robust in its XMODEM handling than the standard (and seemingly only readily available) XMODEM utility for Unix systems, rx—but in what way? Does anyone have any idea of what might be going on here?
unicode_rose
 
Posts: 1
Joined: July 3rd, 2018, 11:56 pm

Re: Can't reliably "Save Floppy" faster than 19200 baud on U

Postby AltairClone » July 11th, 2018, 10:41 am

I have confirmed the "Save Floppy" XMODEM transfer still works at 115,200 baud in the latest Clone firmware with a PC running TeraTerm or HyperTerm.

I have a Raspberry Pi but haven't played with it in a long time. I'll try firing it up soon and try to duplicate your problem.

Meanwhile, there are others on this forum using a Mac and Raspberry Pi for a console, hopefully they'll see this thread and chime in as well.

Mike
AltairClone
Site Admin
 
Posts: 332
Joined: April 5th, 2013, 10:55 am

Re: Can't reliably "Save Floppy" faster than 19200 baud on U

Postby TomXP411 » July 11th, 2018, 12:48 pm

Try a different USB to serial adapter. I've discovered that my original FTDI adapter has failed. it gives me the positive side of the signal, but not the negative (voltage drops to zero on a mark.)

New adapters made all those problems go away for me. I think I also got a speed boost, but I can't remember the best speed my adapters could handle. It was nowhere near the several megabits they're theoretically capable of, though.
TomXP411
 
Posts: 17
Joined: March 8th, 2018, 4:13 pm

Re: Can't reliably "Save Floppy" faster than 19200 baud on U

Postby AltairClone » July 14th, 2018, 11:33 pm

I set up a Raspberry pi (model 3b, Raspbian) and have no problem with XMODEM receive (rx) at any baud rate including 115,200. I ran the receive from within minicom, as an exec rx within screen, and rx stand-alone.

However, I can duplicate your error output at any baud rate if I initiate the receive on the pi before initiatiating the send on the Clone.

Mike
AltairClone
Site Admin
 
Posts: 332
Joined: April 5th, 2013, 10:55 am


Return to General Discussions

Who is online

Users browsing this forum: No registered users and 2 guests

cron