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acadiel

TI-74 and cassette capabilities

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Inside the cartridge. Note, it's 256K total. The address space for this unit was only 32K for the cart port. There has to be some banking scheme going on here to support all 256K. Also, note a power connector is on the board.

 

Note, the last vendor to sell accessories, High-Tech Solutions, dropped their website a long time ago. Here's a historical list of what they sold as far as accessories: http://web.archive.org/web/20090105151147/http://www.hightechsolutions.com:80/Accessories.htm

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46 components on this CI-7 cassette cable:

 

17 resistors

14 capacitors

4 inductors (blue)

5 transistors

4 diodes

1 CA358E RCA601 8 pin IC

1 74HC367E logic chip

 

Plus the cable, 10 pin connector, etc.

 

I’m willing to help board this out! Ksarul or Brain, have any time? :-)

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Since the CI-7 is unobtainium and I don't have access to one to reverse engineer I took a different route. I dug out a Commodore C2N Datasette and milled out an adapter PCB (card edge) to plug into the original connector. I've done some testing to characterize the current draw on the C2N which requires 6V for the motor and 5V for the logic. I have a few different PChannel mosfets on the way to try for automatically controlling the power to the motor (the C2N is high side switched.) I have not found any reference as to which data line is the cassette remote trigger but it should be easy to figure out.

 

In my application the TI-95 has a 6VDC input on the expansion connector so the calculator can be powered by the same external power source that is used for motor power. Darn, I just remembered I forgot to order a LDO 5V regulator for the 5V supply to the C2N...

 

Hopefully this weekend I'll have time to test it out on my TI-95 Procalc.

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I have one too new in box as a matter of fact :) I always found the PCIF to be more practical for file storage and transfers on the TI74 however.

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I'm working with a TI-95 Procalc right now and I don't think it will work, out of the box, with the PCIF. The TI-95 programming manual eludes to the fact that you can run machine code from a RAM cartridge but makes no mention of how to create said code. Trying to do something like that through the key-stoke programming would be painful I think.

​If anyone want to sell or loan a CI-7 I would like to get my hands on one for a while just to sketch out the circuitry. There is just no information about it out there, the pictures on this post are the best I found but the components are too densely packed on the top to see the traces or read component values from the picture.

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I'm working with a TI-95 Procalc right now and I don't think it will work, out of the box, with the PCIF. The TI-95 programming manual eludes to the fact that you can run machine code from a RAM cartridge but makes no mention of how to create said code. Trying to do something like that through the key-stoke programming would be painful I think.

 

​If anyone want to sell or loan a CI-7 I would like to get my hands on one for a while just to sketch out the circuitry. There is just no information about it out there, the pictures on this post are the best I found but the components are too densely packed on the top to see the traces or read component values from the picture.

 

I have never tried using the PCIF with the TI-95. When I have a few moments I'll have to check and see. It might be possible at a minimum to LIST to the PCIF.

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Thanks, it would be interesting to know what it might do. I understand not wanting to open your new CI-7, no worries. Maybe acadeil can take some more photos of all around the board which might be sufficient.

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I did just find and look at the PCIF manual: https://computerarchive.org/files/mirror/ftp.whtech.com/hexbus_cc40_ti74/PC%20Interface%20(PCIF)%20manual.pdf. It has a section on using PCIF with the TI-95 and includes a program listing for saving/loading programs over PCIF. Great, now I need to get an old DOS machine running and build a PCIF interface...

I believe there is a schematic out there for a replacemnent interface. And no need for an old DOS PC. There is a modern update to the transfer software here: http://pengels.bplaced.net/index.php/tiif
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Hey there! Got your email, but have been so busy, I haven’t responded yet. I’ll take a whole bunch of high res pictures and put them on Dropbox this weekend.

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Hey there! Got your email, but have been so busy, I haven’t responded yet. I’ll take a whole bunch of high res pictures and put them on Dropbox this weekend.

 

Thanks! I just tried my Ozark-Engineered Commodore C2N to TI-95 adapter and it does work just fine. I can save and load programs to cassette. Of course it requires two bench power supplies and a few meters of cables to make it work :)

 

I confirmed that:

Pin3 (D0) is the input signal from the cassette adapter

Pin5 (D2) is the remote control to turn cassette motor on/off

​Pin6 (D3) is the output signal to the cassette adapter

 

All data lines float high (5V). The remote control line, Pin5 (D2), floats high and goes low to turn off power to the cassette motor. Having it float high provides power to position the tape. The TI-95 gives you a prompt to position the tape, you click on OK after it is positioned and then it will pull Pin5 (D2) low and prompt the user to press Play. You press play on the cassette deck and then click OK which will bring Pin5 (D2) back high and power the cassette motor.

 

​I don't have the cassette motor remote controlled yet. I did get a box from Mouser today which has a few different logic level mosfets to try out. I forgot to order a LDO 5V regulator so it will be another week or so before I have a completed adapter board. I also picked up a few different types of 10pin connectors to try for use on the TI-95/TI-74 expansion connector.

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I milled out the 'final' PCB today. The top side looks a bit messy as I did a crude 'rub out' tool path to get all the copper out between the fingers on the card edge connector. On the bottom side I did a ground 'pour' so the rub out removed mostly just the copper between the fingers on the card edge. Since it is 'mechanically etched' the holes are not plated through so the handful of vias have to have wired passed through and soldered to both sides (this also limits you to no having vias under components.)

 

I'll get it built up and tested later this week. Luckily I found a 6V wall wart power supply in my junk box I can use.

 

 

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Milling PCB's is so much neater and easier than the old chemical etching method I use... What kind of milling equipment are you using?

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Milling PCB's is so much neater and easier than the old chemical etching method I use... What kind of milling equipment are you using?

 

I use a Taig CNC mill with my own stepper control box and Mach 3 (or Mach 4). I started using a Taig machine about 10 years ago at work on a research project and was so impressed I wound up starting a company on the side to sell them. (That first Taig is still being used every day to making everything from PCBs to microwave waveguides.) Having all the holes drilled and the board routed to shape is also a big bonus in my book :) If you want to check out my website (as long as it is OK to toot my own horn here) it is Soigeneris.com . I have some OLD videos on YouTube under my Soigeneris account. (My new videos about hobby stuff including this are under Jeffrey Birt, I know clever name for a YouTube channel :) )

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Yeah, getting into CNC milling is not cheap, but it is fun :)

 

I have to do one more board version. When I prototyped the circuit on the breadboard I was just using a single 5V source and when I laid out the PCB I forgot to pull the MOSFET up to the 6V rail, not the 5V. That was an easy fix on the current PCB though. I had some strange troubles where it would work then not and I had some conflicting readings at times. I finally realized there was some smoltz between traces, it was too small to see but it was pulling down the PN2222 output that switches the MOSFET.

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Here is a video on the completed interface. There is a link in the description to the design files and BOM on GitHub. The attached picture shows my test set up, the little blue box is the adapter.

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Great job!

 

The only difference between yours and the TI one is the Hexbus pass through, which was probably half the circuitry in the TI one.

 

Sent from my moto x4 using Tapatalk

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Thanks guys. I did not see a bus pass-through on the CI-7. I did get a PC-324 printer in the mail yesterday though and noticed it has a pass-through so you can daisy chain peripherals.

 

Speaking of the PC-342, what type of thermal paper does it take. As I recall there are a few main types and the wrong stuff can ruin a print head.

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