The reverb effect simulates the sound that results from reflections from surrounding walls.
To simulate it most digital reverbs produce two parts: the early Reflections and the reverb component, which are just the signal delayed with different timings.
Reverb.ino uses the 2 DACs to create this two components: DAC0 generates the early reflections and DAC1 does the reverb component (which is the early reflections with more delay). Both components are adjusted independently using POT0 and POT1:
- Pot 0: Adjusts the first reflection of the sound.
- Pot 1: Adjusts the second reflection of the sound.
- Pot 2: Controls the output volume.
- Mix Switch: Shoud be ON (down) to add the direct sound trajectory.
- Toggle Switch: Switchs betseen reverb(delayed signals) and super-reverb(echoed signals).
reverb.ino:/* reverb.ino creates two copies of the guitar signal to be delayed independently producing
a reverb-like sound, the toggle switch selects between delaying or echoing the signals*/
// Licensed under a Creative Commons Attribution 3.0 Unported License.
// Based on rcarduino.blogspot.com previous work.
// www.electrosmash.com/pedalshield
int in_ADC0, in_ADC1; //variables for 2 ADCs values (ADC0, ADC1)
int POT0, POT1, POT2, out_DAC0, out_DAC1; //variables for 3 pots (ADC8, ADC9, ADC10)
int LED = 3;
int FOOTSWITCH = 7;
int TOGGLE = 2;
#define MAX_DELAY_A 20000
#define MAX_DELAY_B 20000
uint16_t DelayBuffer_A[MAX_DELAY_A];
uint16_t DelayBuffer_B[MAX_DELAY_B];
unsigned int DelayCounter_A = 0;
unsigned int DelayCounter_B = 0;
unsigned int Delay_Depth_A, Delay_Depth_B;
void setup()
{
//turn on the timer clock in the power management controller
pmc_set_writeprotect(false);
pmc_enable_periph_clk(ID_TC4);
//we want wavesel 01 with RC
TC_Configure(TC1,1, TC_CMR_WAVE | TC_CMR_WAVSEL_UP_RC | TC_CMR_TCCLKS_TIMER_CLOCK2);
TC_SetRC(TC1, 1, 238); // sets <> 44.1 Khz interrupt rate
TC_Start(TC1, 1);
// enable timer interrupts on the timer
TC1->TC_CHANNEL[1].TC_IER=TC_IER_CPCS;
TC1->TC_CHANNEL[1].TC_IDR=~TC_IER_CPCS;
//Enable the interrupt in the nested vector interrupt controller
//TC4_IRQn where 4 is the timer number * timer channels (3) + the channel number
//(=(1*3)+1) for timer1 channel1
NVIC_EnableIRQ(TC4_IRQn);
//ADC Configuration
ADC->ADC_MR |= 0x80; // DAC in free running mode.
ADC->ADC_CR=2; // Starts ADC conversion.
ADC->ADC_CHER=0x1CC0; // Enable ADC channels 0,1,8,9 and 10
//DAC Configuration
analogWrite(DAC0,0); // Enables DAC0
analogWrite(DAC1,0); // Enables DAC0
//Pin Configuration
pinMode(LED, OUTPUT);
pinMode(FOOTSWITCH, INPUT);
pinMode(TOGGLE, INPUT);
}
void loop()
{
//Read the ADCs
while((ADC->ADC_ISR & 0x1CC0)!=0x1CC0);// wait for ADC 0, 1, 8, 9, 10 conversion complete.
in_ADC0=ADC->ADC_CDR[7]; // read data from ADC0
in_ADC1=ADC->ADC_CDR[6]; // read data from ADC1
POT0=ADC->ADC_CDR[10]; // read data from ADC8
POT1=ADC->ADC_CDR[11]; // read data from ADC9
POT2=ADC->ADC_CDR[12]; // read data from ADC10
}
//Interrupt at 44.1KHz rate (every 22.6us)
void TC4_Handler()
{
//Clear status allowing the interrupt to be fired again.
TC_GetStatus(TC1, 1);
//Check the TOGGLE SWITCH and select between super-reverb and reverb.
if (digitalRead(TOGGLE))
{
//Store current readings in ECHO mode
DelayBuffer_A[DelayCounter_A]=(in_ADC0 + (DelayBuffer_A[DelayCounter_A]))>>1;
DelayBuffer_B[DelayCounter_B]=(in_ADC1 + (DelayBuffer_B[DelayCounter_B]))>>1;
digitalWrite(LED, HIGH);
}
else
{
//Store current readings in DELAY mode
DelayBuffer_A[DelayCounter_A] = in_ADC0 ;
DelayBuffer_B[DelayCounter_B] = in_ADC1 ;
digitalWrite(LED, LOW);
}
//Adjust Delay Depth based in POT0 and POT1 position.
Delay_Depth_A =map(POT0>>3,0,512,1,MAX_DELAY_A);
Delay_Depth_B =map(POT1>>3,0,512,1,MAX_DELAY_B);
//Increse/reset delay counter.
DelayCounter_A++;
DelayCounter_B++;
if(DelayCounter_A >= Delay_Depth_A) DelayCounter_A = 0;
if(DelayCounter_B >= Delay_Depth_B) DelayCounter_B = 0;
//Calculate the output as the sum of DelayBuffer_A + DelayBuffer_B
out_DAC0 = (DelayBuffer_A[DelayCounter_A]);
out_DAC1 = (DelayBuffer_B[DelayCounter_B]);
//Add volume feature based in pot2 position.
out_DAC0=map(out_DAC0,0,4095,1,POT2);
out_DAC1=map(out_DAC1,0,4095,1,POT2);
//Write the DACs
dacc_set_channel_selection(DACC_INTERFACE, 0); //select DAC channel 0
dacc_write_conversion_data(DACC_INTERFACE, out_DAC0);//write on DAC
dacc_set_channel_selection(DACC_INTERFACE, 1); //select DAC channel 1
dacc_write_conversion_data(DACC_INTERFACE, out_DAC1);//write on DAC
}
You can listen how this
Reverb effect sounds in SounCloud.
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