Turntable USB interface

I would like to retro-fit my 1970's pioneer turntable to be able to record onto a iPod or other USB device.

Operation

• Plug in USB stick or iPod
• Press record-pause
• Place stylus on a chosen track
• Signal level threshold trigger changes to record when the stylus hits the record
• Sound file is written onto the device
• Signal level threshold trigger stops recording after a few seconds pause (manual pause provided also)

Systems

• Power supply
  • plug pack 12V 100mA
  • Split from it's case and wired in parallel on the AC side of the turntable's main transformer
• Analogue phono stage (requires ±12V DC)
  • to be build on veroboard
• ICSP programmer required to completely rewrite the bootloader - AVRISP mkII

Microcontroller

• Blackfin
• Arduino NG AVR microprocessor board
• Schematics

Features

• ATmega168 AVR processor
• Digital <-> Analogue converter
• C library and compiler supplied as open source
• AVR emulator
• AVR libC

Operating system

• gcc, libc supplied and open source
• No real operating system required
• svn tree
• bootloader supplied and open source
• libipod [tar] program to modify iPod's XML playlist file to add the newly created track to the playlist

Main loop

• boot up

• USB device?
• loop
  • yes-mount fs and open file descriptor
  • no-loop

• set led to Red
• loop
  • check A to D for signal input
  • check threshhold
    • begin recording
    • or
    • loop
• begin recording

References

• Lots of GNU tools for AVR
• AVR diagrams (good)
• Custom power supply project
• Good links and downloads for emulators, libc...