Guitar Tuner
ECE 5330
Embedded Systems Design
Final Project Proposal
Mike Heiny
November 17, 2008
Background
• I used to play guitar, 20 to 25 years ago.
• But I stunk.
• And I always had trouble tuning.
• I still have my guitar and amp, though.
• I’ve seen electronic tuning gadgets used by roadies at concerts, seems like an interesting thing to design.
Basic Proposal
• Implement hardware to allow connecting an electric guitar to the board.
• User selects which string is to be tuned.
• User plays the string.
• AVR “listens” to the note and communicates to the user, via LEDs, how close to perfect the note is and whether it is high or low.
Hardware
Software
TBD 1
• What is the output of an electric guitar?– I think I read +/- 5 mV was typical– That’s too small to be much use and will have
to be amplified.– Does it put that out with no input, or will I need
to power it somehow?
TBD 2
• How accurate does it need to be?– Strings are 82, 110, 147, 196, 247 & 330 Hz.
(I was really surprised at how low they are.)– When you tune you can hear the wah-wah-
wah of interference. – That’s noticeable to about once every 3 or 4
seconds, which would be ~0.3 Hz. – If I shoot for within 0.1 Hz of target, that’s
0.03%, which is pretty tight.
TBD 3
• Determining Frequency– I plan to have the AVR determine the period
of the input signal and from that determine the frequency.
– But the difference in periods between 330 Hz and 330.1 Hz is less than 1 μs!
– I think this is the biggest challenge.
Other TBDs
• How should the board communicate to the user?
• What will it do when no note is played, and how will it know?
• How will it start and end?
Possible Additional Features
• Add a microphone to allow acoustic guitar tuning.
• Have the program automatically detect which string is being tuned.
• Allow user-specified target frequencies for tuning basically anything.
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