Building a VersaTerm - A Retro Computing Serial Terminal

[Editor]

In the early computing days of the late 1970's, back when we were building our own 8-bit microprocessor systems, it may be hard to imagine now, but we didn't actually have computers back then (of course!).

Sometimes, when we want to feel a bit more nostalgic, it would be nice to be able to fire-up a completely standalone dedicated Serial Terminal system, for talking to our retro 8-bit microprocessor creations.

Join me, as I walk through my assembly of a VersaTerm serial terminal, and get reminded of a "good practice", via a timely busy end of year project assembly lesson! Here: Building a VersaTerm - A Retro Computing Serial Terminal

[bugeyedcreepy]

Yep, stick with the meticulous builds, i find them therapeutic, and of course now stands as an instructive step-by-step for my own MECB Christmas present builds...!

[Editor]

Yep, stick with the meticulous builds, i find them therapeutic, and of course now stands as an instructive step-by-step for my own MECB Christmas present builds...!

It seemed to take me weeks to finish this video. It's been a busy end of year! So, I'm glad it's been enjoyed by a few.

The good news is that I already have plans for the next four videos, which are all more directly MECB related. I just need to get myself through the holiday period, and then I can hopefully be back more fully up-and-running for the new year.

[bugeyedcreepy]

It seemed to take me weeks to finish this video. It's been a busy end of year! So, I'm glad it's been enjoyed by a few.

The good news is that I already have plans for the next four videos, which are all more directly MECB related. I just need to get myself through the holiday period, and then I can hopefully be back more fully up-and-running for the new year.

Well, Keep it up, I say - you're on the right track. As much as I might be impatient, we do understand there's only one of you...!

[antijn]

Very interesting video, was looking for something like the VersaTerm myself.
Do you know what voltage the VersaTerm outputs on the RS232 port? I've found some older hardware that needs the positive and negative levels to be more than the cheaper USB to serial converters deliver.
Also, in your video I could only see a few of the lower baudrates like 2400, but the documentation for the VersaTerm mentions as low as 50 baud. Was that only an effect of how you cycled the speeds (i.e. pressing keys to find the baudrate) or is there some other config needed for the less usual baudrates?
I'll see if I'll build one for myself, and I'll have a look at your other videos.

[Editor]

Very interesting video, was looking for something like the VersaTerm myself.
Do you know what voltage the VersaTerm outputs on the RS232 port? I've found some older hardware that needs the positive and negative levels to be more than the cheaper USB to serial converters deliver.

I haven't used the RS232 interface myself yet (only the TTL interface). However it is driven by a MAX3232 based module, which the data sheet says "Meets or exceeds the requirements of TIA/EIA-232-F and ITU V.28 standards"

Also, in your video I could only see a few of the lower baudrates like 2400, but the documentation for the VersaTerm mentions as low as 50 baud. Was that only an effect of how you cycled the speeds (i.e. pressing keys to find the baudrate) or is there some other config needed for the less usual baudrates?

Yes, I was just looking for the baud rate I wanted. The baud rate setting does allow me to scroll through 19 pre-set baud rates from 50 baud to 921600 baud, and you can also select "Custom", where you enter the baud rate you want. Presumably also allowing non-standard baud rates.

I'll see if I'll build one for myself, and I'll have a look at your other videos.

It was a fun project, and is proving useful for my retro computing fun.

[antijn]

Very interesting video, was looking for something like the VersaTerm myself.
Do you know what voltage the VersaTerm outputs on the RS232 port? I've found some older hardware that needs the positive and negative levels to be more than the cheaper USB to serial converters deliver.

I haven't used the RS232 interface myself yet (only the TTL interface). However it is driven by a MAX3232 based module, which the data sheet says "Meets or exceeds the requirements of TIA/EIA-232-F and ITU V.28 standards"

I looked at the MAX3232 module like on https://www.sparkfun.com/products/11189 and the datasheets to that SP3222EB/3232EB chip specifies TxOUT as +/- 13.2V, which is better than the USB to serial converters I mentioned.

Also, in your video I could only see a few of the lower baudrates like 2400, but the documentation for the VersaTerm mentions as low as 50 baud. Was that only an effect of how you cycled the speeds (i.e. pressing keys to find the baudrate) or is there some other config needed for the less usual baudrates?

Yes, I was just lookign for the baud rate I wanted. The baud rate setting does allow me to scroll through 19 pre-set baud rates from 50 baud to 921600 baud, and you can also select "Custom", where you enter the baud rate you want. Presumably also allowing non-standard baud rates.

Cheers, it did look like there was something else happening there.

Thanks again for the video.

[Editor]

I looked at the MAX3232 module like on https://www.sparkfun.com/products/11189 and the datasheets to that SP3222EB/3232EB chip specifies TxOUT as +/- 13.2V, which is better than the USB to serial converters I mentioned.

Yes, that datasheet looks more informative than the MAX3232 datasheet I had found.

But, I note that the 13.2v is an "Absolute Maximum" rating. Also, "NOTE 1" states: "V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V."

The "DRIVER OUTPUTS" Electrical Characteristics has "Output Voltage Swing" Typical as +-5.4V (Min +-5.0V). Which is therefore what I'd expect in normal operation.

Although, I haven't yet measured it in actual use, or remember what typical old-school RS232 ports require.

However, I do remember we used to drive our RS232 ports with the old-school MC1488 driver IC, which we typically powered with +-12V (and paired it with the MC1489 receiver IC), before the world was taken over by the single 5V MAX232.

Thanks again for the video.

You're welcome. Thanks for watching, and commenting!

[Writerbenjamin]

The GitHub page said due to limited memory, there is no 132 column mode. Is there now enough resources if I use a Raspberry Pi Pico 2 instead? If so, which file should I edit to use 132 column mode.

[Editor]

The GitHub page said due to limited memory, there is no 132 column mode. Is there now enough resources if I use a Raspberry Pi Pico 2 instead? If so, which file should I edit to use 132 column mode.

A good question. I don't know the answer. I'd suggest perhaps posting the question as an issue on David Hansel's VersaTerm github repository to see if he can advise on this?
132 column capability would be nice to have, but would require higher resolution than the current 640 wide VGA resolution the current system is based on.
https://github.com/dhansel/VersaTerm