Send and receive bytes with the pidp-8 via a serial port

[Roberto]

Hello everyone 

Happy new Year and thanks for including me in this group.

I would like to send and receive bytes with the pidp-8 via a serial port.

I know it should be a fairly simple thing but I am not very familiar with Raspberry.

I have successfully connected the PDP 8 to an ampex serial terminal via a USB / rs232 adapter. But I can't find a simple way to receive and send bytes to an external serial device.

Thanks a lot 

Roberto

[timr...@gmail.com]

First of all what OS will you run on it?  OS/8?  TSS/8?  Something else?  I'd think you'd need to add a line to the startup script of the OS of choice to 

allow connection to your terminal.  You also need to find out what device the USB is at.  Usually I do a "ls -lrt /dev/tty*" and see what's last before plugging

in the USB cable.  Then plug it in and see if a new device appears.  If it does this should be your USB device to use.  I have not set up a real terminal to

mine so I tell you perfectly what to do next.  I should plug in a real VT125.  :)

[Roberto]

Thanks for the reply.

From the serial terminal I can access the Raspbian command line, and then I can switch to OS/8. My serial device is ttyUSB0.

What I would like to do is to leave the pidp8 free from operating systems and program it only with the switches from the panel. I would not like to have a terminal connected but a serial device like Arduino that receives and transmits bytes to the pidp-8.

[Roberto]

By the way, a V125 terminal is wonderful!!!! 🤩

[timr...@gmail.com]

This should be what you want to do then:  "set console serial=/dev/ttyUSB0;1200-7e1".  This will move the console that you used to be able to access from the Pi and

make it talk to your "real" console.  I found this here: https://tangentsoft.com/pidp8i/wiki?name=Serial+or+Telnet+PDP-8+Console .  I am pretty sure I tried this once

and it does work.  You'd have to put this in the boot script.  I think I tried it outside of it after it was up and running and that works too but only til you boot again.  So I had to add it to the boot script.  Programming from the front panel is fun for a while.  I had to do it many times on a real 8i.  You will have to set your terminal to the same baud rate for this to work. 110 and 300 are way too slow.  9600 is nice but not sure if system will keep up.  Could try 2400 too.  Good luck.

[Roberto]

Thanks!!

The command always returns invalid argument. Am I doing something wrong? Is that the right place to put it?

[Rick Murphy]

Do you have a /dev/ttyUSB0?

Try "ls /dev/tty*" before and after you insert the USB serial device.
I think the device node will get created upon inserting the USB device, and it may not be ttyUSB0. 

    -Rick

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Rick Murphy, D. Sc., CISSP-ISSAP, K1MU/4, Annandale VA USA

[timr...@gmail.com]

I have tried this on mine and get the same thing.  Mine shows as /dev/ttyUSB0.  I have a real serial terminal that I know works fine.  I modified the boot script

to add this.  I run TSS/8 and you need to see the initial prompt to start up the system.  It never displays.  Tried with and without a null modem.  It works fine if

I run the pdp8 code on Linux.  Pretty sure I did this once before but too long to remember. The system was already running and I changed it and I got it to display

to the screen.  Now I am stumped.

[Roberto]

Hi Rick, yes, it shows the name we expected: ttyUSB0. It only exists when the USB device is connected

[timr...@gmail.com]

I had tried the same thing on my pidp-10 and it worked just fine.

[Roberto]

So the Pidp8 seems to have a problem with this, how else can I send bytes to a serial port?

[Roberto]

I did it!! In another way, I followed this method here: https://groups.google.com/g/pidp-8/c/gRNj35He-dM/m/dXxtMiuLAAAJ

[Roberto]

In the example they used:
attach ttix 1234
to connect to telnet port 1234.
And that works.

But what if I want to connect to a serial port instead of telnet?

Something like that for reading?
attach ttix line=0,connect=ser1

And for writing?
attach ttox line=0,connect=ser1 (gives error)

Thanks 

[Roberto]

Now everything works, it's enough:
attach ttix line=0,connect=ser1

both for reading and writing.
thanks a lot to everyone!!

[timr...@gmail.com]

Is there a way with this attach statement to change the baud rate?  It seems to default to 9600 and I think that is too fast for an 8.  I have tried several approaches but none are accepted.  Just trying to get a real serial terminal connected via a USB to serial cable.  I know the terminal works and the cable works as I have used it elsewhere.  I plugged in two short USB-A to -A to the Pi and out thru the back so I don't have to keep removing the back.  TIA.

[Roberto]

You can add:
attach ttix line=0,connect=ser1;1200-7e1

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[timr...@gmail.com]

That does not seem to work for me.  When I add the ";1200-7e1" it errors out with an Unexpected Identifier 1200-7e1.

[Roberto]

You can put it in 0.script

In my case it is found in: opt/pidp8i/share/boot/0.script

Also check that Ser1 is correct, you can use the show serial or show devices command, I don't remember exactly which one.

I wasn't interested in keeping the console on the Pi, so I didn't try, but you could try adding another line with TTI instead of TTIX. But it's just a guess.

Let me know if it works, I'll be interested in adding the terminal soon.

To view this discussion visit https://groups.google.com/d/msgid/pidp-8/e49df4bd-df4c-4112-b5fb-4df7f0875d24n%40googlegroups.com.

[timr...@gmail.com]

I got this to work today.  I had my stop bits on the VT-125 set to two instead of 1.  I was able to log two users into TSS/8.  One on the console of K00 and the second onto 

K01.

[Roberto]

Great job!