CVSD audio compression codec in an FPGA

In this video Jeri Ellsworth demonstrates her design of a Continuously Variable Slope Delta (CVSD) audio compression codec in an FPGA. She was in need of a replacement for a damaged HC-55564 IC from (where else) a pinall machine and reverse engineered the chip, coding up a replacement in a Xilinx FPGA on a Papilio One dev board.

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  1. Hi Jeri – Great explination of this type of CVSD audio circuit!

    Have you ever come across a CVSD IC with the part number MC34115P? this was a Motorola type chip used as a Digital to analogue decoder inside a type of laser tag system called Q-Zar. However the company has since long gone. I have some M27C2001 Eproms with the speech on them, but have no way of knowing how to encode new speech. From looking at the MC34115P datasheet, these IC’s can also act as encoders as well! Problem is trying to store the encoded audio as a serial stream that can be re-programed back into an Eprom!

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