RS232 to real TTY

[WatsonAC79]

Hi all!

I have a real teletype I would like to demo for the IMSAI and the teletype; interactive is awesome.

Naturally it requires a serial to CL which is all in working order. Known because it communicates fine with my HAM shack, a radio,TNCs, etc...

I have it running 1200 baud, yeah slow but older things in my collection are what they are and kinda set the standard - also still faster than 45.5 baudot...

I have the patch jumpers all correct, I also installed the jumpers for CTS/RTS (top 4 jumpers). That signal is how my setup manages to throttle 1200 bps down to 45.5 with a very limited buffer memory.

So I am getting intelligible output (baud settings, check! And short text like the cp/m banner and prompt, check!) But, if I run something like a DIR.... I get the beginning and end characters and a lot missing in the middle. Checked with the web TTY versus what printed.. I believe it acts like it plows through the output without halting on the pause from the terminal hardware pulsing out the baudot. So, flow control, hmmm...

Am I missing something? I see a jumper on the boot jumper panel that looks promising but I can't find documentation on that or to validate installing the patch jumpers would be the only step I needed.

[WatsonAC79]

Follow up: just rediscovered external serial buffers/spoolers existed in the way back. Going to try that in lieu of the flow control working, directly.

It will certainly be a thing for the external device to use the hardware flow control and that will solve my limited buffer in the serial to CL box. I can queue up miles of ascii before this taps out...

Could nearly spit, that means I can bring my baud up in the rest of the shack and let the device do its job for the Teletype only.

[donfroula]

That’s interesting. I had a couple of ASR33 Teletypes back in the day. They ran natively in 7 bit ASCII, rather than Baudot (upper case only). The rate was 110 baud with one start and two stop bits with even parity. It used a 20mA current loop I had cobbled together with a few Darlington transistors. It worked well on a Commodore 64, as it had a software UART that could run at 110 baud with the plug-in RS-232 interface cart.

I was able to use the IMSAI 8080 replica second serial port to work in XY Basic using XON/XOFF handshaking and a 9600 baud serial voice synthesizer, but did not find a way to address the CTS/RTS pins through the Z-80 software ports. I think it is possible, but poorly documented, if at all.

Don

[WatsonAC79]

That's good stuff! I'm running a m15, a 33TD and 33 reperf in my shack, so have it all set up on 60mA and it's 5 level. I happen to have the translation device run a relay in a home brew current loop to get a full power signal through the things on the Rx side. The Tx loop is easy without help even with low voltage.

Would love to have room for a 7 or 8 level ASR for real ascii without translation step

Still working on putting a spooler in to take page(s) of characters before it hits the real bottleneck of 45.5 Baudot and slamming out on paper.

I also discovered with my laptop that I get partial or failed output unrelated to the flow control. I have flow control with the laptop. DIR works on the webtty but I only get some or none doing the same thing over serial. XDIR works on both. Sdir only on Webtty. So. That's next to figure out after the spooler.