6 replies to this topic

[Martin]

I have idea about the possibility to play sound on fx9860 G SD and I need your opinion.
1. Audio files will be stored on the SD card as the internal flash is not large enough.
2. The format will be mono, 4bit per sample, 22 kHz, but may be better. I am not sure if the CPU (at max speed) is able to decode MP3, but it is too early for this question :-)
3. As an output device ("sound card") we use serial port, it will work as 1 bit DAC. We need to output data in very high speed ~ Mbit/s
4. We fill serial FIFO by DMA.
5. The main routine will read data from SD card in suitable sized data chunks and convert it.
6. Simple stereo headphones with 2.5 stereo jack would play (of course only 1 headphone would play), but simple low pass filter is preferred.

As I wrote above I need your opinion:
a. Do we want it? Simple cheap MP3 player produces much better sound.
b. Is it possible to put together?
b1. What is the max data rate of the sio ?
b2. What is the read speed of the SD card. We need 25 ~ 50KB/s
b3. Can we use DMA for sio in addon app ?
c. What important I have forgotten ?

Please excuse me if this topic was already discussed elsewhere.

[alias4399]

This would create an EXPLOSION if you could play sound from the calculator. I do not think this has been discussed before. If you could pull this off, Martin.. it would be incredible.

[ECE]

6. Simple stereo headphones with 2.5 stereo jack would play (of course only 1 headphone would play), but simple low pass filter is preferred.

The serial port sends packets in certain Casio protocol in a Digital format (square waves). How are you going to send an analog sound wave directly to the speaker?

Regards.

[Distortion]

I believe I accidentally stumbled upon a thread where kucalc was talking about playing wav files on a calculator.
Of course, I can't find it anymore...

IIRC the project was discontinued without a given reason.

[noname11]

This was already done for the AFX series of calculators:
Marco's homepage: http://www.pageofmarco.de/sound.php3
UCF discussion: http://www.casiocalc...?showtopic=2015

[Martin]

This was already done for the AFX series of calculators:...

Yes, but it is something like midi player.
I would like to create something like wav player.

[Martin]

I have created simple demo, which can demonstrate quality of the playback.
It is very simple quick and dirty program for windows. To try it you need:
1. COM->jack converter, ugly schematics is at http://www.rkk.cz/~m...0snd/scheme.gif.
2. Sample audio - convert some mp3 file to wav format, mono, 8bit per sample, 44100 samples/second.
I used disk writer plugin in winamp, screenshot of settings is at http://www.rkk.cz/~m...0snd/format.gif
3. Compile program from http://www.rkk.cz/~m...0snd/comsnd.cpp,
change the #defines for com name, speed and audio file as you need.

Standard PC serial ports work at maximum speed 115200 which is already set in my program. If you have something better - for example many USB->COM cables or PCI card with additional COM ports are able to operate at 230400 (use #define COM_SPEED COM_SPEED_DOUBLE) or at 460800 (use #define COM_SPEED COM_SPEED_QUAD),try it.
Higher speed means better quality, which is very terrible for standard bit rate 115200 because you can hear byte frequency here (speed/10~ 11 kHz).
Playing modes:
at 115200: 11520 samples/second, 3 bit
at 230400: 23040 samples/second, 3 bit
at 460800: 23040 samples/second, 4 bit

Please use cheap low quality headphones at least for the first try :-)