Fret scanners and pickups for stringed instruments
Techniques are described that relate to various aspects of converting the mechanical energy of instrument strings to digital representations for use in a variety of applications.
1. A stringed instrument, comprising:
a body, the body having a bridge and a saddle mounted thereon;
a neck and a headstock, a nut being disposed where the neck and the headstock meet, the headstock having a plurality of tuning machines mounted thereon;
a fretboard mounted on the neck and the body, the fretboard extending from the nut and having a plurality of electrically conductive frets;
a plurality of electrically conductive strings, each string extending from a corresponding one of the tuning machines, over the nut, parallel with the fretboard, over the saddle, and being secured to the bridge; and
fret scanning circuitry configured to conduct a sequence of full board scans, each full board scan including selectively applying drive signals to the strings, selectively measuring fret signals resulting from the drive signals for adjacent pairs of the frets, and generating fret data using the fret signals, the fret data representing one or more fret hits, each fret hit representing a corresponding one of the pairs of frets bridged by a corresponding one of the strings, wherein the fret scanning circuitry is further configured to compare the fret data for consecutive full board scans, determine that an amplitude of a first fret signal for a first pair of frets and a first string and representing a first fret hit declines by less than a dithering gap amount for each of a first number of the consecutive full board scans, and retain the first fret hit as a valid fret hit even if the amplitude of the first fret signal falls below a fret hit threshold.
2. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to release the first fret hit after the first fret signal declines by less than the dithering gap amount for each of a second number of the consecutive full board scans.
3. The stringed instrument of claim 2 , wherein the first number is greater than or equal to a programmable dither threshold count, and the second number is greater than or equal to a programmable dither timeout count.
4. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to determine, before starting to determine that the amplitude of the first fret signal declines, that the first fret hit was reported in at least one previous full board scan, and that a number of simultaneous fret hits are currently being reported.
5. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to determine that an amplitude of a second fret signal for a second pair of frets and the first string exceeds an amplitude threshold higher than the fret hit threshold, the second pair of frets trailing the first pair of frets.
6. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to register the first fret hit only if the first fret hit exceeds the fret hit threshold for a third number of the consecutive scans.
7. The stringed instrument of claim 6 , wherein the fret hits correspond to different note transition types, and wherein the fret scanning circuitry is further configured to employ different consecutive scan thresholds to register a fret hit for the different note transition types.
8. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to determine, for each of the strings, if the string is being touched but not fretted.
9. The stringed instrument of claim 8 , wherein the fret scanning circuitry is configured to determine, for each of the strings, if the string is being touched but not fretted by charging the string, generating a value representing the charge on the string, and comparing the value to a touch scan threshold.
10. The stringed instrument of claim 1 , wherein the fret scanning circuitry is further configured to vary the fret hit threshold based on a number of the strings being simultaneously fretted.
11. A fret scanning system for use with a string instrument having a plurality of electrically conductive frets and a plurality of electrically conductive strings, the fret scanning system comprising circuitry and one or more processors configured to use the circuitry to conduct a sequence of full board scans, each full board scan including selectively applying drive signals to the strings, selectively measuring fret signals resulting from the drive signals for adjacent pairs of the frets, and generating fret data using the fret signals, the fret data representing one or more fret hits, each fret hit representing a corresponding one of the pairs of frets bridged by a corresponding one of the strings, wherein the one or more processors are further configured to compare the fret data for consecutive full board scans, determine that an amplitude of a first fret signal for a first pair of frets and a first string and representing a first fret hit declines by less than a dithering gap amount for each of a first number of the consecutive full board scans, and retain the first fret hit as a valid fret hit even if the amplitude of the first fret signal falls below a fret hit threshold.
12. The fret scanning system of claim 11 , wherein the one or more processors are further configured to release the first fret hit after the first fret signal declines by less than the dithering gap amount for each of a second number of the consecutive full board scans.
13. The fret scanning system of claim 12 , wherein the first number is greater than or equal to a programmable dither threshold count, and the second number is greater than or equal to a programmable dither timeout count.
14. The fret scanning system of claim 11 , wherein the one or more processors are further configured to determine, before starting to determine that the amplitude of the first fret signal declines, that the first fret hit was reported in at least one previous full board scan, and that a number of simultaneous fret hits are currently being reported.
15. The fret scanning system of claim 11 , wherein the one or more processors are further configured to determine that an amplitude of a second fret signal for a second pair of frets and the first string exceeds an amplitude threshold higher than the fret hit threshold, the second pair of frets trailing the first pair of frets.
16. The fret scanning system of claim 11 , wherein the one or more processors are further configured to register the first fret hit only if the first fret hit exceeds the fret hit threshold for a third number of the consecutive scans.
17. The fret scanning system of claim 16 , wherein the fret hits correspond to different note transition types, and wherein the one or more processors are further configured to employ different consecutive scan thresholds to register a fret hit for the different note transition types.
18. The fret scanning system of claim 11 , wherein the one or more processors are further configured to determine, for each of the strings, if the string is being touched but not fretted.
19. The fret scanning system of claim 18 , wherein the one or more processors are configured to determine, for each of the strings, if the string is being touched but not fretted by charging the string using the circuitry, generating a value representing the charge on the string, and comparing the value to a touch scan threshold.
20. The fret scanning system of claim 11 , wherein the one or more processors are further configured to vary the fret hit threshold based on a number of the strings being simultaneously fretted.