Re: tape storage details (first release)

[Ricardo Bittencourt Vidigal Leitao]

        Hello people.

        I just made the first release of CAS Tool, my utility to read MSX
tapes in any computer. As I said before, the input file for CAS Tool MUST
BE a 44kHz, signed 16-bit, mono .WAV file. 

        In this first release, the data contained in the .WAV must be
stored in 1200 bauds. The output is not a valid .CAS file yet, instead the
program just stores all the demodulated data in the output file.

        The program has a very strong signal regenerator (I spent some
hours in MatLab designing this filter). My input test was a 10-year-old
MSX tape, digitalized through the MIC-IN input of my SB32PnP. 

        Since this release doesn't output a valid .CAS, I didn't send it
through e-mail to the people who asked for. Instead, you can get it at the
Brazilian MSX Software home page:

        http://www.lsi.usp.br/~ricardo/msx.htm

        Source code is included. (while you're in this page, check "Video
Player" and "RB two-liners", released last week) 

        Some people asked about the method used by the BIOS to store the
information. It uses FSK (frequecy shift keying). FSK is very simple: when
you want to store a bit "0", just write a 1200 Hz wave in the tape. To
store a bit "1", just write a 2400 Hz wave. The headers are just long
strings of bits "1". The data bytes are stored with a start bit "0", then
comes the eight bits (LSb first), and then two "1" stop bits.

------------------------------------------------------------
Ricardo Bittencourt           http://www.lsi.usp.br/~ricardo
[EMAIL PROTECTED]    "Save the trees: eat more woodpeckers"


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