[posted] Strobe Tuner for Guitar based on Teensy 3.6


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I have built a strobe tuner based on Teensy 3.6, two shift registers and 16 LEDs. It simulates the rotating disc of a strobe tuner with the shift registers used as a circular buffer. The signal from the electric guitar is preamplified with the board seen on the right. The signal then goes into the analog input of the Teensy. The string of the guitar is detected using the YIN algorithm implemented in the Teensy Audio Library. According to the string the reference frequency is created by Teensy and it is used to shift a single one through the circular buffer. The processed guitar signal is used for the "output enable" pin of the shift registers. If the two signals (reference and guitar) have the same frequency the illuminated LEDs seem to stand still. If the guitar is out of tune, the LED pattern seems to go left or right, depending on the frequency difference.

You can find the project on github:

Does your tuner have a means to determine how many cents it's off, or be able to set it to x-cents off?

Years ago I worked with an organ technician who had a "home built" organ tuner that showed tuning by LEDs for each 12 notes and cents "error" on a meter marked +50 to -50, as some oscillators had to be adjusted x-cents off the standard notes. It didn't use a computer chip but "standard" TTL chips from the 70's. I think it used a PLL technique.
Awesome! I love seeing Teensy guitar stuff! It's truly the best platform I've found for this type of realtime audio processing effects.