Ghost Code
100% digital remake of my ghostCODE reverb pedal that detects the frequency of the reverberated signal and uses divisions of that frequency to control a tremolo. The rate of the tremolo will increase as you play faster notes, giving you strangely interactive but slightly random-feeling pulses of reverb.
note - "freeverb" in the diagram is a placeholder for the Plate Reverb object
I've used Piotr (of Hexe Guitar)'s open source plate reverb code as my reverb. It sounds much better than the two options in the GUI in my opinion. You need to create the plate reverb library to use the Ghost Code sketch (scroll down to see how to do this)
The reverb on each channel is fed back into itself via mixer1 and mixer3. The volume on each mixer controls the feedback level.
Each channel's reverb is then lowpass filtered (biquad1 and biquad3) and sent to a notefreq object that detects the frequency of the reverb signal. That frequency is then divided (by a division selected with a pot) and the waveform object is then set to the divided frequency.
The waveform is mixed with DC object (essentially a constant level of 1) to create the depth pot. The waveform's offset is set to 1 to make a tremolo sound (rather than a ringmod). Turning down the depth pot increases the DC object's volume and decreases the waveform's volume until the mixer outputs a constant 1 (giving a passthrough effect at the multiplier).
The output of this mixer is multiplied with the reverb signal to create the tremolo. The reverb then goes through a final lowpass filter (controlled with a pot) and an amp for some make up gain.
Due to digital noise creeping in with too big of a program, each channel's division is done by the left channel. It works well as a mono in/stereo out effect. You could potentially use a control signal in the left channel to control the tremolo on the right.
Creating the plate reverb library
This is the exact same method you'll use for creating a library for any effect not included in the Teensy Audio Library. It's the same method I described in the Vibrato sketch description but I'll go through it again here.
First create a new sketch in the Arduino IDE (File -> New)
In the top right of the IDE you'll see a drop-down arrow under the magnifying glass, click it, and click 'New tab'.
In the box that appears, type "effect_platervbstereo.h", then click 'OK'. This will be the header file that will accompany the ".cpp" library file you're about to create.
Open this link to Piotr's plate reverb code, and open the two links called effect_platervbstereo.h and effect_platervbstereo.cpp.
Copy the entirety of the ".h" code sample into this new tab, deleting everything that was there previously.
Click back to the first tab that opened in the IDE, probably named "sketch_(today'sdate)", under the upload and verify buttons.
Copy everything in the ".cpp" code example from Piotr's github into this tab, deleting everything that was there previously.
Next you'll need to check what your "sketchbook directory" is, this is the location on your device that your sketches are saved to. In the IDE, go to File -> Preferences -> Sketchbook location. It's probably "...Documents/Arduino" but it's good to make sure.
Now save the sketch you just created (File -> Save). Make sure the sketch is being saved in your sketchbook directory. There is another folder called "libraries" in "Program Files x86" (on Windows). You need to make sure you save the sketch in the correct "libraries" folder in "Documents" - assuming that's what your sketchbook directory is - and not the Program Files x 86 one. Name the sketch "effect_platervbstereo.cpp" and save it.
Open File Explorer on your computer and navigate to your sketchbook directory, then open the "libraries" folder. You should now see a new folder called "effect_platervbstereo.cpp". Open this folder and check that you have two files, "effect_platervbstereo.h" and "effect_platervbstereo.cpp". If the latter appears as "vibrato.cpp.ino", rename it by removing the ".ino". Click "OK" if a warning pops up.
The Plate reverb library is now created and you can use this awesome effect :)
Ghost Code Sketch
Copy everything in the embedded box below into a new Arduino sketch and zap it into your pedal to play with the Ghost Code!
A0 = Feedback, A1 = Tone, A2 = Division (there are four: /64 /32 /16 /8), A3 = Depth
Toggle switch = “Alt” division (/32 /16 /8)
Footswitch turns on “Alt” division
#define LED 3
#include <Bounce.h>
#include "effect_platervbstereo.h"
#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
// GUItool: begin automatically generated code
AudioInputI2S i2s1; //xy=227.1110610961914,444.5555610656738
AudioSynthWaveformDc dc1; //xy=491.2221450805664,436.66667556762695
AudioSynthWaveform waveform1; //xy=498.2221450805664,503.66667556762695
AudioEffectPlateReverb freeverb2; //xy=517.7777709960938,762.2222900390625
AudioMixer4 mixer3; //xy=518.2221946716309,691.6666736602783
AudioEffectPlateReverb freeverb1; //xy=521.2221946716309,165.66667366027832
AudioMixer4 mixer1; //xy=531.2221946716309,241.66667366027832
AudioMixer4 mixer2; //xy=636.2221450805664,463.66667556762695
AudioFilterBiquad biquad1; //xy=741.1110916137695,161.11109828948975
AudioEffectMultiply multiply1; //xy=815.5555258856879,317.777778201633
AudioEffectMultiply multiply2; //xy=817.7777252197266,622.2222585678101
AudioAnalyzeNoteFrequency notefreq1; //xy=923.3333511352539,158.8888931274414
AudioFilterBiquad biquad2; //xy=958.8888778686523,320.0000343322754
AudioFilterBiquad biquad4; //xy=971.1110382080078,618.8888845443726
AudioAmplifier amp1; //xy=1112.2223739624023,321.11109924316406
AudioAmplifier amp2; //xy=1127.7777557373047,613.3333530426025
AudioOutputI2S i2s2; //xy=1330.7777290344238,467.55562019348145
AudioConnection patchCord1(i2s1, 0, mixer1, 0);
AudioConnection patchCord2(i2s1, 1, mixer3, 0);
AudioConnection patchCord3(dc1, 0, mixer2, 0);
AudioConnection patchCord4(waveform1, 0, mixer2, 1);
AudioConnection patchCord5(freeverb2, 0, mixer3, 1);
AudioConnection patchCord6(freeverb2, 0, multiply2, 1);
AudioConnection patchCord7(mixer3, freeverb2);
AudioConnection patchCord8(freeverb1, 0, mixer1, 1);
AudioConnection patchCord9(freeverb1, 0, multiply1, 0);
AudioConnection patchCord10(freeverb1, biquad1);
AudioConnection patchCord11(mixer1, freeverb1);
AudioConnection patchCord12(mixer2, 0, multiply1, 1);
AudioConnection patchCord13(mixer2, 0, multiply2, 0);
AudioConnection patchCord14(biquad1, notefreq1);
AudioConnection patchCord15(multiply1, biquad2);
AudioConnection patchCord16(multiply2, biquad4);
AudioConnection patchCord17(biquad2, amp1);
AudioConnection patchCord18(biquad4, amp2);
AudioConnection patchCord19(amp1, 0, i2s2, 0);
AudioConnection patchCord20(amp2, 0, i2s2, 1);
AudioControlSGTL5000 sgtl5000_1; //xy=1292.666603088379,783.6667251586914
// GUItool: end automatically generated code
Bounce footswitch = Bounce(0, 50); // debounce the footswitch
Bounce D1 = Bounce(1, 50); // debounce the toggle switch
Bounce D2 = Bounce(2, 50); // " " " " " " " " "
// this section includes the function to check the toggle position
bool right;
bool middle;
bool left;
void checkToggle () { // this is our function to check toggle position...
D1.update(); D2.update(); // check digital inputs connected to toggle (can delete I think)
if(digitalRead(1) && !digitalRead(2)) {right = 1; middle = 0; left = 0;} // toggle is right
if(digitalRead(1) && digitalRead(2)) {right = 0; middle = 1; left = 0;} // toggle is in the middle
if(!digitalRead(1) && digitalRead(2)) {right = 0; middle = 0; left = 1;} // toggle is left
}
// variables
float reverbtime;
float note;
byte division;
int lpf;
float depth;
extern "C" uint32_t set_arm_clock(uint32_t frequency);
void setup() {
set_arm_clock(146000000);
AudioMemory(450); // the "40" represents how much internal memory (in the Teensy, not the external RAM chip) is allotted for audio recording. It is measured in sample blocks, each providing 2.9ms of audio.
sgtl5000_1.enable(); // this turns on the SGTL5000, which is the audio codec on the audio board
sgtl5000_1.volume(1); // this sets the output volume (it can be between 0 and 1)
sgtl5000_1.inputSelect(AUDIO_INPUT_LINEIN); // selects the audio input, we always use Line In
analogReadResolution(12); // configure the pots to give 12 bit readings
pinMode(0, INPUT_PULLUP); // internal pull-up resistor for footswitch
pinMode(1, INPUT_PULLUP); // internal pull-up resistor for toggle
pinMode(2, INPUT_PULLUP); // internal pull-up resistor for toggle
pinMode(3, OUTPUT); // pin 3 (the LED) is an output;
// test stuff
sgtl5000_1.adcHighPassFilterDisable();
sgtl5000_1.audioPostProcessorEnable();
sgtl5000_1.audioPreProcessorEnable();
sgtl5000_1.autoVolumeEnable();
// sine wave / note detection
waveform1.begin(1, 5, WAVEFORM_SINE);
notefreq1.begin(.60);
// input / feedback mixer
mixer1.gain(0,1);
mixer3.gain(0,1);
// plate verb settings
freeverb1.size(1);
freeverb2.size(1);
// pre-note-freq reverb filter
biquad1.setLowpass(0, 1000, 0.7);
// reverb output hpf
biquad2.setHighpass(0, 120, 0.8);
biquad4.setHighpass(0, 120, 0.8);
//depth
dc1.amplitude(1);
waveform1.offset(1);
// make-up gain
amp1.gain(2);
amp2.gain(2);
}
void loop() {
// feedback
reverbtime = (float) analogRead(A0) / 4095;
mixer1.gain(1,reverbtime*1.45);
mixer3.gain(1,reverbtime*1.45);
// low pass filter
lpf = (analogRead(A1) * 2) + 1000;
biquad2.setLowpass(1, lpf, 2.2);
biquad4.setLowpass(1, lpf, 2.2);
if(!digitalRead(0)) // if footswitch pressed
{
digitalWrite(LED, HIGH);
checkToggle();
if(right) division = 2;
else if(middle) division = 3;
else if(left) division = 4;
}
else {
division = 7 - ((analogRead(A2) >> 10) +2); // pot controls division, 5 to 2
digitalWrite(LED, LOW);
}
// read fundamental frequency
if (notefreq1.available())
{
note = notefreq1.read();
//division
division = 2 << division; // the 4 divisions are 64 to 8
// set waveform frequency
note = note / division;
waveform1.frequency(note);
}
// depth
depth = (float) analogRead(A3) / 4095;
mixer2.gain(0,1-depth);
mixer2.gain(1,depth);
}
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