ASR-33 Teletype w/Imp005

A friend of mine got a hold of an old ASR-33 Teletype. Mechanically it seems to be in good condition. Lucky for him it has the 20ma current loop bulkhead on the back (the ones with the Call Control Units didn’t always have the 20ma interface).

The 20ma current loop is easy to adapt to RS232 voltage levels using hardware. Lots of circuits available to do the conversion. But it is still 110 baud. That is hard to work with because no modern micro controllers have baud rate settings that low. Except … I now see the Imp005 (and only the Imp005), will be able to set UART1 as low as 35 baud. So I assume it can be set to 110 baud with 8 data bits, 1 start and 2 stop bits.

Now the question is about the Imp005 and whether or not developers will ever be able to find one mounted on a board that is usable, like the Imp003. It would be so perfect to be able to communicate at 110 baud without any hacking an old Hayes SmartModem, which is the path we started taking.

The “dream” would be to get my hands on an Imp005 mounted on a board with all of the necessary hardware for the power supply, SPI Flash Ram, blink-up, etc.

Is this a dream I will ever realize in my lifetime?

If there was enough interest, I would be willing to fab and assemble some imp005 breakouts (per reference design) for sale to developers.

I do have to say the 005 performance is awesome. Can’t wait for i2c update though.

Is it purely an input device?
At that sort of speed could you consider using the sampler at 440Hz or even 330Hz. The imp003 should be powerful enough to scan the blob for bytes before a buffer overflow occurs.

At 330Hz, you’d scan a full buffer for a low ADC value for the beginning of the start bit, then read off the 4th, 7th, 10th, 13th… and 25th for your byte and check that the 28th value is high to confirm your stop bit.

I believe we have imp005 breakout boards coming in the very near future. Not sure of the suppliers who will be selling it, but I would imagine it will be the usual suspects (eg. Digi-Key)

@coverdriven, It is send/receive (both ways).
@smittytone, Thanks for that heads-up. Will be interesting to see how pricing will be.

I have an old Tandy Model 200 (TRS-80). That vintage portable can do 110 baud. We will try getting the RS232 voltage conversion board working while we wait for a possible Imp005 breakout. At least he can work on the mechanics. Like others in his situation, he spends most of the time looking for OEM parts, sometimes really hard to find at a decent price. Our goal is to get a modern interface without modifying the original hardware (as minimal as possible). The Imp005 seems to be promising.