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PIC-Controlled Guitar Tuner

Boring stuff / legal stuff

This is an old, unmaintained project that was finished March 1997. I put it here on the server because I was asked to. BTW: I still use the tuner - it works fine for me

• Note: The sourcecode is documented in german, as I am too lazy to translate it. So there is still some work left for you...
• Another note: Ofcourse I don't take any responsibility for damages to your health or your guitar or your favourite pet or whatever you like.
• important note: If you think you can make lots of money with this - go ahead. Send it to me. This is my IP.
• most important note: This project is not maintained any more - at least not by me. If you have improvements - go ahead and put them into this wiki.

The schematic and the asm-file should only give you an idea how to build a simple tuner. This is not for people who are not into assembler programming or hardware.

Some words about the tuner

This was the first hardware I built - a guitar tuner controlled by a 16C84 from Microchip. The incoming signal is filtered by a 3rd order low pass and transformed into a square-wave with the frequency of the key-note. The controller measures the frequency of the signal and compares it to the nominal frequency. The detected tone is displayed and the deviation to the key-note is displayed by a bargraph. The display is a HD44780-based LCD module with 2x8 characters.

The first line of the display shows the 7 notes (c,d,e,f,g,a,h,c) and a status field that displays a '#' for a detected haftone, a '?' for an invalid measurement or '+' or '-' for an invalid frequency. The center of the second line represents the center-frequency of the detected key-note with '   ><   '. For example if the the measured frequency was exactly an 'e', the cursor would blink on the first line on the 'e', and the second line would show '   ><   '. If the tuning was little too low it would display '   #<   '. This scheme is used to increase the number of steps for different deviations.

The following table shows the "bargraph" display for increasing deviatons:

too low	too high
'   ><   '	'   ><   '
'   #<   '	'   >#   '
'  ##<   '	'   >##  '
' ###<   '	'   >### '
'####<   '	'   >####'
'### <   '	'   > ###'
'##  <   '	'   >  ##'
'#   <   '	'   >   #'

This picture shows a nearly exactly tuned 'e' (little too low)

files

• sg.asm: assembler code for the pic controlled guitar tuner
• sg3.png: schematic of the pic controlled guitar tuner

-- MatthiasWientapper - 24 Jun 2002