Author Topic: Serial Link, TI Z80  (Read 2322 times)

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Offline Xeda112358

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Serial Link, TI Z80
« on: July 15, 2015, 10:29:19 am »
I was not sure where to post this, but I made a calc-to-calc serial cable!

I ended up finding two sets of headphones with the right size tips (not sure what they are called), so I cut them up with an ample length of wire. I also have a bunch of jumper wires that I got for my Raspberry Pi, so after cutting the headphone wires, I exposed the three sets of wire, used an abrasive to strip off the enameling, and spliced each wire with a female tip of a jumper wire. From there, I can connect them with male-male jumpers and it properly transmits data between my calcs!

The reason that I didn't just splice the two sets of wires together directly is because now I can plug in other items. For example, I connected male leads to an electric motor and LED-- it lets me control them through the link port now! I can also hook them up to a breadboard if I wanted to, making it possible to connect more calculators, or I can directly plug them into the GPIO board on my Raspberry Pi. A few months ago I did this and wrote a Python program and a calc program that could communicate with each other (basically just sending a string in Ans to the Pi, and have it displayed in the terminal).

Unfortunately, I lost the Python program due to a crash, but I still have the calc programmed backed up on calc. My plan is to come up with some working routines from scratch since I am still pretty terrible with figuring out the link port. It took me forever to figure out that the receiving calc can't change the lines.

Offline Hooloovoo

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Re: Serial Link, TI Z80
« Reply #1 on: July 15, 2015, 11:46:05 am »
Cool! I picked up a couple of TI link cables and connected them together for calcnet, and I also put some bare wires on them for Floppytunes and connection to other things. I soldered them together because my splicings were somewhat unreliable.

Link routines are annoying. With the way current routines work, you can only send data one direction at a time, and all kinds of other goofiness. It would be cool if we could connect the Pi's GPIO to the calc for Tilp sending though.
"My world is Black & White. But if I blink fast enough, I see it in Grayscale." -tr1p1ea
Spoiler For some of the calcs I own:



(actually I have quite a few more than this, but I don't feel like making bars for them all.)

Offline Xeda112358

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Re: Serial Link, TI Z80
« Reply #2 on: July 15, 2015, 12:31:38 pm »
Yeah, I should solder them as the connection was shaky before I taped them. I was going to, then I never got to it XD

I think the issue with the link routines and only being able to send one direction at a time is a hardware issue. I've tried changing the lines using the "receiving" calculator and it doesn't work. I think it's that it can't change it from a 0 to a 1 unless it was the calc that set it to 0 (by sending a 1).

I dunno, it was a pain in the butt, but I did find the program I was working on, which is awesome. It can send and receive bytes or packets of data and allows the user to exit the receiving end by pressing Clear if there is no activity (so no infinite loops!). Currently I can just send a string in Ans from one calc to the beginning of RAM, but that is only because I didn't have access to a computer at the time I made it and couldn't remember the _CreateStrng bcall.

My plan is to make a link protocol where a calc can:

-Send a packet of data to be written to predetermined location in RAM
-Send a file to another calc
-Request from the other calc a file
-Request a list of files (for FileSyst, this would allow the other calc to inspect folders in order to make requests for files).
-Request current key presses

Offline Hooloovoo

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Re: Serial Link, TI Z80
« Reply #3 on: July 15, 2015, 12:45:35 pm »
You can only pull the lines down (I don't remember if that's a 1 or 0 in port 0 though) on the calculator side, and you should only pull the lines down on the Pi side, and leave them high otherwise. You may need a pullup resistor on the Pi though.

If you have 2 (or more) calculators, if any calculator pulls a line low by outputting to port 0, all calculators see the change, and the line doesn't go high again until all calculators let the line float.

With the way the calculator is set up, it would be pretty hard to do full-duplex transmitting anyway. Usually protocols use at least 2 wires and a ground. It's possible that we could get some kind bidirectional 1-wire interface running, one wire each way, but I don't really see the point when half-duplex is much easier and probably faster.
"My world is Black & White. But if I blink fast enough, I see it in Grayscale." -tr1p1ea
Spoiler For some of the calcs I own:



(actually I have quite a few more than this, but I don't feel like making bars for them all.)

Offline Art_of_camelot

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Re: Serial Link, TI Z80
« Reply #4 on: July 15, 2015, 05:05:27 pm »
Pretty neat stuff Xeda! :D

Offline Sorunome

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Re: Serial Link, TI Z80
« Reply #5 on: July 15, 2015, 06:22:25 pm »
sounds quite fun indeed! :D

Also those cables are 2.5mm audio jack, as opposed to the "normal" 3.5mm variant

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Offline Minty

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Re: Serial Link, TI Z80
« Reply #6 on: November 07, 2015, 12:42:00 am »
Could I use two of these hooked together with a usb female to female adapter?

Offline Sorunome

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Re: Serial Link, TI Z80
« Reply #7 on: November 07, 2015, 03:36:42 am »
i doubt that would work due to the chips in between, you could cut off the 2.5mm audio ends and solder them together though.

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Offline Geekboy1011

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Re: Serial Link, TI Z80
« Reply #8 on: November 07, 2015, 09:10:10 am »
That would most definetily not work due to how the Silverlink works @Minty !. That being said. Link cables are cheap enough on ebay. If you shop around something to the tune of less then $2usd a piece.

As for @Xeda112358 How did your link shenanigans go? I will honestly suggest looking into CalcNet2.2 by KermM It fits most of your criteria ;P and from personal experience is pretty robust and fast. I do realize that would have been outside of the scope of you making your own to learn though~

Offline Xeda112358

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Re: Serial Link, TI Z80
« Reply #9 on: November 07, 2015, 10:44:07 pm »
I originally made the Python program to experiment with the GPIO board on my raspberry pi. I eventually managed to create working link routines between calcs and played with those, but I never did anything substantial. The routines, however, were significantly faster than other routines I have seen, and I think I posted them somewhere.