output constant value

[AutoEM]

Hi,
I am using an external dac (PCM5102-DAC-Decoder) with esp32, and would like to output a constant voltage for device control.
This library seems perfect since esp32 internal dac is only 8 bits.
The following code seems to work and outputs positive voltages only. I am just changing the fi value in a loop
for demonstration purposes...
I was just left to wonder is there a more clever way to do this?

#include "AudioTools.h"
AudioInfo info(8000, 2, 16);
GeneratorFixedValue<int16_t>  GFixed;
GeneratedSoundStream<int16_t> sound(GFixed);
I2SStream out; 
StreamCopy copier(out, sound);                             // copies sound into i2s

int16_t fi=0;

void loop1(void *pvParameters){  
  while (1) {
    
    GFixed.end();
    GFixed.setValue(fi);
    GFixed.begin();
    
    copier.copy();

    fi+=100;
    if(fi>=32700)fi=0;
  }
}

void setup(){
  I2SConfig config = out.defaultConfig(TX_MODE);
  config.copyFrom(info);
  config.pin_bck = 27;
  config.pin_ws = 25;
  config.pin_data = 26;

  out.begin(config);

  xTaskCreatePinnedToCore(loop1, "loop1", 4096, NULL, 1, NULL, 1);
 
}

[pschatzmann]

I would suggest to use a dedicated library for motor control instead: they are usually using PWM.

If you want to experiment with this library for this purpose I would suggest the following options:

• try to use an AnalogAudioStream as output to use the internal DAC
• try to use a PWMAudioOutput to use potentially any pin
• in loop1 just do the copier.copy in the loop and define fi as volatile
• define the copy size in the constructor of StreamCopy to make it more responsive

[AutoEM]

Thanks for the swift answer pschatzmann!

I am not using a motor. I am controlling a high voltage device, where an 0 to 5v input voltage gives 0 to 40 kV output voltage. Though I only need half of it, so input 2.5V max is fine. The input voltage should be stable and slowly changing, when I update [Acc_V_End] it via esp32 wifi. It should not go to zero between copier.copy() commands. I am not really sure if I understand how this library works, but that is why i call the copier.copy() command twice in the thread.
However in the end I want to control 2 high voltage supplies. In the below code I try to control two devices with the GFixed 1 and 2
generators. I am trying to set GFixed1 to left channel and GFixed2 to right channel. I figured maybe 'ChannelsSelectOutput' could do this, but apparently the signals are weirdly mixed with the below code.
How could i separate the signals using only one i2sStream?

Thanks in advance!

p.s. my loop() function is also quite crowded, this is why i am using a thread....

#include "AudioTools.h"

AudioInfo info(8000, 2, 16);
GeneratorFixedValue<int16_t>  GFixed1,GFixed2;
GeneratedSoundStream<int16_t> sound1(GFixed1),sound2(GFixed2); 
I2SStream i2s_1; 
ChannelsSelectOutput out;
StreamCopy copier1(out, sound1); 
StreamCopy copier2(out, sound2);  

int16_t V_step=80;
volatile int16_t Acc_V_Current=0, Acc_V_End=0, WhC_V_Current=0, WhC_V_End=0;

unsigned long previousMillis = 0;
unsigned long interval = 1000;

void loop1(void *pvParameters){ 
  while (1) {
    
    copier1.copy();
    copier2.copy();

    if(Acc_V_End!=Acc_V_Current) 
    {
      unsigned long currentMillis = millis();
      if (currentMillis - previousMillis >= interval) {
     
        GFixed1.end();
        GFixed2.end();

        if( abs(Acc_V_End-Acc_V_Current) <= V_step){ GFixed1.setValue(Acc_V_End);Acc_V_Current = Acc_V_End;}
        else if(Acc_V_End>Acc_V_Current) { GFixed1.setValue(Acc_V_Current + V_step); Acc_V_Current += V_step;}
        else { GFixed1.setValue(Acc_V_Current - V_step); Acc_V_Current -= V_step;}
        GFixed2.setValue(20000);

        GFixed1.begin();
        GFixed2.begin();
        previousMillis = currentMillis;
      }
    }

    copier1.copy();
    copier2.copy();
  }
}


void setup(){

  I2SConfig config1 = i2s_1.defaultConfig(TX_MODE);

  config1.copyFrom(info);
  //config1.port_no = 0;
  config1.pin_bck = 27;
  config1.pin_ws = 25;
  config1.pin_data = 26;

  i2s_1.begin(config1);

  out.addOutput(i2s_1, 0,0);
 // out.addOutput(sound2, 1,1); crash!
  out.addNotifyAudioChange(i2s_1);

  out.begin(info);

  GFixed1.setValue(0); 
  GFixed1.begin();
  GFixed2.setValue(0); 
  GFixed2.begin();

  xTaskCreatePinnedToCore(loop1, "loop1", 4096, NULL, 1, NULL, 1);
}

void loop(){

}

[pschatzmann]

I suggest that you stick with the standard Arduino functionality: this makes it much simpler!

The ESP32 analogWrite() uses PWM. On other microcontrollers you can also use analogWrite() to write to the dac pins.
On the ESP32 you will need to use the dacWrite(uint8_t pin, uint8_t value) method instead.

I guess for your purpose PWM would be good enough, but you might need to use a RC (resistor-capacitor) filter to get a stable voltage if the high frequency PWM is disturbing.

[AutoEM]

Hi

using esp32 internal dac is only 8bit, giving too small output precision (40000/256) for my needs.
Anyways, for those with similar goals - here is the working version of the code. I managed to get it working
using the InputMerge class. I update the 'Acc_V_End' and 'WhC_V_End' values via WIFI connection (not shown here).
The 'V_step' controls how fast the voltage ramps up or down. GFixed1 goes to left channel and GFixed2 to right, and
you can update them independently.
I have not played around with the sample_rate (here 10000) and StreamCopy buffer_size (default 1024) and I dont
know if it is necessary to call copier1.copy() twice in the thread.

#include "AudioTools.h"

AudioInfo info_out(10000, 2, 32); // using 32bit (PCM5102-DAC-Decoder)
AudioInfo info_in(10000, 1, 32);
GeneratorFixedValue<int32_t>  GFixed1,GFixed2;
GeneratedSoundStream<int32_t> sound1(GFixed1),sound2(GFixed2);             // Stream generated from sine wave
I2SStream i2s_1; 
InputMerge<int32_t> imerge(sound1, sound2);
StreamCopy copier1( i2s_1,imerge);  

int32_t V_step=10000000;
// PCM5102 gives negative to positive output, if your dac gives only positive - use uint32_t
volatile int32_t Acc_V_Current=0, Acc_V_End=0, WhC_V_Current=0, WhC_V_End=0; 

unsigned long previousMillis = 0;
unsigned long interval = 1000;

void loop1(void *pvParameters){
  while (1) {
    
    copier1.copy();

    unsigned long currentMillis = millis();

      if (currentMillis - previousMillis >= interval) {

        if( Acc_V_End!=Acc_V_Current) 
        {
        GFixed1.end();
       
        if( abs(Acc_V_End-Acc_V_Current) <= V_step){ GFixed1.setValue(Acc_V_End);Acc_V_Current = Acc_V_End;}
        else if(Acc_V_End>Acc_V_Current) { GFixed1.setValue(Acc_V_Current + V_step); Acc_V_Current += V_step;}
        else { GFixed1.setValue(Acc_V_Current - V_step); Acc_V_Current -= V_step;}

        GFixed1.begin();
        }

        if( WhC_V_End!=WhC_V_Current) 
        {
        GFixed2.end();

        if( abs(WhC_V_End-WhC_V_Current) <= V_step){ GFixed2.setValue(WhC_V_End);WhC_V_Current = WhC_V_End;}
        else if(WhC_V_End>WhC_V_Current) { GFixed2.setValue(WhC_V_Current + V_step); WhC_V_Current += V_step;}
        else { GFixed2.setValue(WhC_V_Current - V_step); WhC_V_Current -= V_step;}
  
        GFixed2.begin();
        }
        previousMillis = currentMillis;
      }
    

    copier1.copy();
  }
}

void setup(){

  I2SConfig config1 = i2s_1.defaultConfig(TX_MODE);

  config1.copyFrom(info_out);
  config1.pin_bck = 27;
  config1.pin_ws = 25;
  config1.pin_data = 26;

  i2s_1.begin(config1);

  GFixed1.setValue(-10); //make output a bit negative instead of positive
  GFixed1.begin(info_in);
  GFixed2.setValue(-10); 
  GFixed2.begin(info_in);

  imerge.begin(info_out);

  xTaskCreatePinnedToCore(loop1, "loop1", 4096, NULL, 1, NULL, 1);
}

void loop(){
}

[pschatzmann]

I would call copy only once and play around with the copy size. Smaller sizes will be more responsive. The default is 1024.

StreamCopy copier1( i2s_1,imerge, 1024);  

I guess in your case the minimum value would be 64 (= 1 frame). With this approach you can also replace the interval logic.