Connect to FX-9750gii through 3pin using audio

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Calculators: Casio fx-9750 G II, Casio fx-9860 GII

Connect to FX-9750gii through 3pin using audio

Postby bleckbleek » Mon Mar 11, 2019 9:40 pm

Hey guys,
I've had this idea for a while now, and I just made an account to ask about it. My plan is to create a phone app that allows you to transmit programs from your phone to your Casio fx-9750 using an Aux Cable and a 3.5mm - 2.5mm adapter.

Let me explain. At school I came across these little robots called Edison Robots. They are programmed with either the python library or using the tactile drag-and-drop IDE. (think Scratch) However the thing that caught my eye was how you put the programs on the calculator. instead of a data cable, they supply a cable with a 3.5mm audio jack on one end and an LED on the other. The LED is held against the robot and the IDE plays a loud audio file which transmits the code. [This is a bit of info I found from the site,][] and it explains that the IDE compiles the code then creates a WAV file.

Now, my big idea is to create a program similar to FA-124 that uses this audio technique to communicate with the 3pin port. The pinout would look like this:
[Computer Left Audio] --- [Calc Receive Data]
[Computer Microphone Input] --- [Calc Transmit Data]
[Computer Ground] --- [Calc Ground]
The program would act like another calculator, as this is what the 3pin port is used to communicate with. I have been messing around with some cables and I have managed to record an audio file of what I assume is the start of a handshake from the calculator. This proves that the data being sent by the calculator can be picked up by a computer if it thinks that the data is actually input from a microphone.

I plan on editing this post and creating others as this is a large project that will take some time. But I would love some feedback or initial thoughts on this idea. Do any glaring flaws jump out? Are there parts that you don't understand and would like me to expand on? I really want to have a discussion about this.

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Calculators: Casio fx-CG 20

Re: Connect to FX-9750gii through 3pin using audio

Postby AmazoNKA » Mon Mar 11, 2019 11:35 pm

Could you clarify please. Will any microphone or speakers be involved? Or just a wire with 3-pin connector going into calculator and some other connectors plugged into computer, i.e. without actual sound?

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Calculators: Casio fx-7400GII, Casio fx-7400GII (SH4), Casio fx-9750 G II, Casio fx-9750 G II (SH4), Casio fx-9860G, Casio fx-9860 G SD, Casio fx-9860G Slim, Casio fx-9860 GII SD, Casio fx-9860 GII SD Power Graphic 2, Casio Classpad 330 plus, Casio fx-CG 20, Casio Classpad fx-cp400, Casio fx-CG 50

Re: Connect to FX-9750gii through 3pin using audio

Postby SimonLothar » Sat Mar 16, 2019 10:09 am

The [Calc Receive Data] and [Calc Transmit Data] ports strictly require TTL-level. This is the baseline, if you don't want to use additional active hardware.
If it is possible to operate the computer audio ports as digital ports at TTL-level, at least the electrical characteristics would match.
The second problem with emulating a serial datastream is the timing. A software emulated serial bit stream must not be interrupted. The width of the serial bits is restricted to a range with low tolerance.
With some single board computer, over which you have full control, it is possible to emulate a serial datastream by software, though this is still less reliable compared to a hardware solution.
With a personal computer a software emulation of a reliable serial datastream with well a defined bit-width is difficult, maybe impossible at all. I am not sure, if you can hinder the kernel to interrupt your software. Moreover you would have to use the microphone input as interrupt driven listener, if you do not want to miss several serial input data.

I'd recommend a hardware solution, t. i. using the ports, which are designed for serial communication. These are very reliable.
I'll be back!

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