MPR121, Daisy Seed, VS Code

Hardware Development
1

Hi, I am relatively new to the Daisy and coding as well.

I managed to build a little synth, and now I want to control it with the MPR121 touch controller.

Unfortunately I cannot find examples for VS Code / C++ so far.

Can someone help me?

Basically I want to trigger “gate” to starte the ADSR and create a pitch for the Osc.

Thanks!

2

Try the Simple Touch examples: GitHub - Synthux-Academy/simple-touch-instruments: Instruments for the Simple Touch board

3

Thanks!
This thing is very adorable.
I had a look into simple-daisy-touch.h, why is it using the adc (and mentions many digital pins as well)?
I expected it to have the mpr121 talk via scl and sda?

4

Because it has slide+rotary pots as user input as well.

It uses the default config in which you don’t have to setup these pins explicitly.

You can find more examples here: GitHub - Synthux-Academy/synthmas-2023: Synthmas 2023 contest results (Simple Touch instruments designed by community members)

5

thank you!

unfortunately these examples are hard to understand, for example simple-touch.h gives no clue if the mpr121 is connected to the correct pins.

anyway, I found a decent Mpr121 tester on github:

but it only triggers on the first 4 pins, while the serial monitor shows that all 12 pins are received.

what could be the problem here? I extended the switch cases, but to no avail.

#include “daisy_seed.h”
#include “daisysp.h”
#include “dev/mpr121.h”

using namespace daisy;
using namespace daisysp;

uint16_t currTouched;
uint16_t lastTouched;

// Define the frequencies for the two octaves surrounding middle C
double scale[12] = {
// Octave below middle C
{130.81, 138.59, 146.83, 155.56, 164.81, 174.61, 185.00, 196.00, 207.65, 220.00, 233.08, 246.94},
// Middle C and the octave above
{261.63, 277.18, 293.66, 311.13, 329.63, 349.23, 369.99, 392.00, 415.30, 440.00, 466.16, 493.88},
// Octave above middle C
{523.25, 554.37, 587.33, 622.25, 659.26, 698.46, 739.99, 783.99, 830.61, 880.00, 932.33, 987.77}};

DaisySeed hw;
Mpr121I2C mpr121;
Oscillator osc;

static void AudioCallback(AudioHandle::InterleavingInputBuffer in,
AudioHandle::InterleavingOutputBuffer out,
size_t size)
{
float sig;
for(size_t i = 0; i < size; i += 2)
{
sig = osc.Process();

    // left out
    out[i] = sig;

    // right out
    out[i + 1] = sig;
}

}

int main(void)
{
hw.Init();
hw.StartLog();
hw.SetAudioBlockSize(4); // number of samples handled per callback
hw.SetAudioSampleRate(SaiHandle::Config::SampleRate::SAI_48KHZ);
hw.StartAudio(AudioCallback);

//How many samples we'll output per second
float samplerate = hw.AudioSampleRate();

// Initialize MPR121 with I2C configuration
Mpr121I2C::Config mprConfig;
mprConfig.transport_config.periph = I2CHandle::Config::Peripheral::I2C_1;
mprConfig.transport_config.speed = I2CHandle::Config::Speed::I2C_400KHZ;
mprConfig.transport_config.scl = Pin(PORTB,8);  // Replace with your SCL pin
mprConfig.transport_config.sda = Pin(PORTB,9);  // Replace with your SDA pin

// Set additional MPR121 configuration if needed
mprConfig.touch_threshold = 12;
mprConfig.release_threshold = 6;

//Set up oscillator
osc.Init(samplerate);
osc.SetWaveform(osc.WAVE_SIN);
osc.SetAmp(1.f);
//osc.SetFreq(440);

if(mpr121.Init(mprConfig) != Mpr121I2C::OK)
{
    // Handle initialization error
    while(1)
    {
        // Error handling code (blinking LED, etc.)
    }
}
// Setup to print 
hw.StartLog();

while(1) 
{
	// Read touch status
    currTouched = mpr121.Touched();

    // Process the touch status as needed
    for(int i = 0; i < 12; i++)
    {
        if((currTouched & (1 << i)) && !(lastTouched& (1 << i)))
        {
            // Channel i is touched, print the channel number
            hw.PrintLine("Channel %d touched", i);
        }
        if(!(currTouched & (1 << i)) && (lastTouched& (1 << i)))
        {
            // Channel i is released, print the channel number
            hw.PrintLine("Channel %d released", i);
        }
    }
    lastTouched = currTouched;

    switch (currTouched)
    {
    case 0:
        osc.SetFreq(scale[0][0]);
        break;
    
    case 1:
        osc.SetFreq(scale[0][1]);
        break;
    case 2:
        osc.SetFreq(scale[0][2]);
        break;
    case 3:
        osc.SetFreq(scale[0][3]);
        break;
    case 4:
        osc.SetFreq(scale[0][4]);
        break;
    case 5:
        osc.SetFreq(scale[0][5]);
        break;
    case 6:
        osc.SetFreq(scale[0][6]);
        break;
    case 7:
        osc.SetFreq(scale[0][7]);
        break;
    case 8:
        osc.SetFreq(scale[0][8]);
        break;
    case 9:
        osc.SetFreq(scale[0][9]);
        break;
    case 10:
        osc.SetFreq(scale[0][10]);
        break;
    default:
        break;
    }
    // Add necessary delay or other code here...
}

}

6

another question, is there pressure sensitivity possible in order to set velocity and sustain level?

(I got this to work by abandoning the switch cases and use is-touched for setting the pitch and gate, and use is-released for releasing the gate)

7

The MPR121 does not register anything like “pressure”. You basically only get on or off.
(there is a “raw” output option, but in practice this doesn’t give any useful value)