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Old 24th Jul 2020, 3:29 pm   #1
Karen O
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Default Kansas City cassette interface

I've been working on this for some time or rather, I built the case and board up about a year ago then lost interest before wiring it up. My interest has been revived by an experiment I want to do using a genuine SC/MP computer.

The design is based around an XR-2206 function generator chip. It works but only after tracing and fixing a timing error It's rather fussy about which cassette recorders it will work with. Your prosaic shoebox player mangles the waveforms too much (zero crossings are shifted and the recovered clock has fierce jitter). By contrast, the ITT model you can see in the photos replays pretty much as recorded.

I'm sure the original designs were as fussy.

The original recommendation required that you tap into the clocks of your UART so that wide tape speed variations can be tolerated. I've designed this one so that you don't have to do that. It seems to work fine using the same player but would probably rule out exchanging tapes with other people.
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Old 28th Jul 2020, 9:56 am   #2
Wendymott
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Default Re: Kansas City cassette interface

Another triumph from Karen (O)....I always look forward to your postings..
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Should get out more.

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Wendy G8BZY
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Old 28th Jul 2020, 1:20 pm   #3
Karen O
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Default Re: Kansas City cassette interface

Thank you Wendy.

Perhaps this marks a change for me - there's not a PIC in sight on this one!
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Old 28th Jul 2020, 2:35 pm   #4
Karen O
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Default Re: Kansas City cassette interface

I've zipped up my circuit drawings for the curious.

Warning: Experimental!

If you want a tried and trusted solution, I recommend Don Lancaster's 'Bit Boffer' article in Byte Magazine March 1976!
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Old 8th Sep 2020, 10:33 pm   #5
Phil__G
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Default Re: Kansas City cassette interface

Karen, I've known a friend Mike on various other forums over many, many years and only last week realised he is Mike Blandford of Cottis-Blandford CUTS fame!
I've used their circuit for packet radio as well as storing programs, I think I was the only 'Cambridge System' user on a CP/M Z80 rather than the ubiquitous Beeb!
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