110 Baud USB to Serial Converter?

General discussions related to the Altair 8800 Clone

110 Baud USB to Serial Converter?

Postby toml_12953 » September 26th, 2015, 7:18 am

I just got a Raspberry Pi and can run my Teletype off it using its built-in serial port and an external serial to current loop converter. The Pi can also use USB to serial converters and I could add a powered USB hub to run ten terminals or more off it. Can you imagine ten terminals run by a $30.00 device? The TTY will be the limiting factor as far as speed goes. The only problem is that most USB-serial adapters are based on an FTDI chip that has a lower limit of 300 baud. The Teletype runs at a fixed 110 baud. Does anyone know of a USB-serial adapter that works at 110 baud?
I've successfully run three terminals on the Pi (one TTY, one ADM5 at 9600 baud and a 300 baud terminal emulator on a PC) and it's quite a sight. If I could run multiple TTYs, I could recreate a minicomputer room of the 60's and 70's with just a Pi! Woo hoo!
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Re: 110 Baud USB to Serial Converter?

Postby AltairClone » September 26th, 2015, 7:53 am

I use serial converters based on the Prolific chip set and they work with a Teletype at 110 baud. However, something in the driver/buffering logic fails if you try to send an entire file (e.g., Altair BASIC) to an Altair at 110 baud or 300 baud. However, on the Pi, it will use the Linux version of the driver instead of the Windows version, so operation may differ.

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Re: 110 Baud USB to Serial Converter?

Postby kwiebe » June 6th, 2019, 8:22 pm

Resurrecting this thread to see if anything has changed or for new info?

Is there a preferred device out there?
-Ken
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Re: 110 Baud USB to Serial Converter?

Postby mcleinn » June 7th, 2019, 6:57 am

For me, the Prolific adapter I got from Mike with the Clone works best & so far in all situations. I used it to send the
paper tapes (4K BASIC etc.) to my punch at 110 Baud & read back the files from the teletype and communicate with
the Altair.

However, I bought another Prolific adapter which doesn't seem as reliable. For example, it would stop the
transaction to my paper punch after the first hundred bytes or so - even though it nominally runs at 110 Baud.

The visual difference between the two adapters is, that the working one has an LED, and the problematic one doesn't.
The working one is identified in Drivers / Driver details / Hardware Ids as USB\VID_067B&PID_2303&REV_0300
The one which seems to make troubles is USB\VID_067B&PID_2303&REV_0400

All the best
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Re: 110 Baud USB to Serial Converter?

Postby AltairClone » June 7th, 2019, 9:43 am

That's good to know about the newer Prolific adapter with the light in it and that it works well at 110 baud even for loading BASIC.

I have not tried 110 baud with a USB adapter since my real business switched to that USB adapter in early 2016. The older Prolific adapter (without the light) would work at 110 baud for typing, but a file send (e.g., sending a 4K BASIC paper tape image) wouldn't work properly.

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Re: 110 Baud USB to Serial Converter?

Postby kwiebe » June 7th, 2019, 12:02 pm

Thanks. I found a potential device and some good info at this link too:

http://www.aetherltd.com/connectingusb.html
-Ken
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