4 bit Digital to Analog converter for TI calculators

keoni29 · Advanced Newbie Joined: 18 Feb 2012 Posts: 41

I made a 4 bit digital to analog converter to use with my calculator. It runs off a 9 v battery regulated down to 5v for the TTL logic.

I made this device to be able to make playing sound samples over the I/O port less cpu intensive. I have not succeeded to play decent sounding samples fetched from my computer yet. The conversion process is very long and the quality of the sample must have degraded along the way.

Some video's of the thing still on breadboards:
It plays nice sawtooth waves.

Link

The first failed attempt to play samples. (well it plays the samples, but the samples are messed up)

Link

I used AXE code to send data to the DAC, but you can use ASM too of course.

I wrote this document with the building instructions/schematics/code:
download

KermMartian · Posted: 12 Jul 2012 12:34:55 pm Post subject:

Cool stuff, and cool demo. What sort of protocol to you use to communicate? Can I safely assume you have a microcontroller, send it a frequency and duration, and that it controls the DAC?
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keoni29 · Advanced Newbie Joined: 18 Feb 2012 Posts: 41

KermMartian · Posted: 18 Jul 2012 06:50:57 am Post subject:

OK, I'll check it out. Out of curiosity, have you had any success in fixing the sounds output to be a bit more correct and clean?
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keoni29 · Advanced Newbie Joined: 18 Feb 2012 Posts: 41

Oh the sound output was just perfect, but the sample data was a mess Sad

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KermMartian · Posted: 18 Jul 2012 03:43:06 pm Post subject:

keoni29 · Advanced Newbie Joined: 18 Feb 2012 Posts: 41

There is no such thing as ONE converter. I used audacity to convert audio to 8 bit raw pcm. Then I used some python code written by jimbauwen to convert it to 4 bits. This data was copied to sourcecoder and converted to an appvar in wabbitemu using axe. There are a ton of things that could have gone wrong Razz

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