651 Neptune guitar tuner (proportional window, version b, debug output on bidir pins, larger set of frequencies)
651 : Neptune guitar tuner (proportional window, version b, debug output on bidir pins, larger set of frequencies)
- Author: Pat Deegan
- Description: It's a guitar tuner! and so much more...
- GitHub repository
- Clock: 1000 Hz
How it works
The rising edge of the input is counted over a set period of time and attempt is made to tell if this count is at, or near, a frequency of interest--namely the E,A,D,G,B notes of guitar standard tuning. In this version, the system should be capable of detecting: E2,A2,A3,B3,D3,E3,G3,D4,E4 and G4 so from about ~80 to 400 Hz. Clock config settings (using 3 input bits) 0: 1kHz 1: 2kHz 2: 4kHz 3: 3.277kHz 4: 10 kHz 5: 32.768kHz 6: 40kHz 7: 60kHz
How to test
Set the clocking bits to 0b000 for a 1kHz clock input (input bits 2,3 and 4). Input pulses are fed to input bit 5. The raw count of pulses over the sampling period (hard-coded here to 0.5 seconds) is output on the bidir pins. The output is setup to drive a dual 7-segment display, or a single 7-segment (by using the output_display bits on the input). In single mode, the 7-seg dot marks exact match.
External hardware
Digital input required: may need massaging if looking at actual guitar signals... see documentation
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | n/a | segment a | raw input pulse count bit 0 |
| 1 | n/a | segment b | raw input pulse count bit 1 |
| 2 | clk config 0 | segment c | raw input pulse count bit 2 |
| 3 | clk config 1 | segment d | raw input pulse count bit 3 |
| 4 | clk config 2 | segment e | raw input pulse count bit 4 |
| 5 | input pulse | segment f | raw input pulse count bit 5 |
| 6 | output display single enable (LOW == dual) | segment g | raw input pulse count bit 6 |
| 7 | output display select | dot or select (for dual) | raw input pulse count bit 7 |