ADC fluctuating beetween floating value and expected value

Troubleshooting
1

Hi everyone, i am currently working on an EMG project and i am trying to send a accurate emg signal from the photon to my computer application, when i am using only one ADC and send the data of it, it looks ok, but when i try to send the data from four adcs it looks like the data from the four ADC’s mix up.
Actually i made a test and even when i set the value of vA0, vA1, vA2, vA3 for 4000,3000,2000,1000 the data i receive is mixed between this values.
here is my code:

//SYSTEM_MODE(SEMI_AUTOMATIC);

TCPClient client;
byte server[] = { 192, 168, 25, 5 };
int an0 = A0;
int an1 = A1;
int an2 = A2;
int an3 = A3;
int an4 = A4;
int16_t n;
byte vA0[200] = {};
byte vA1[200] = {};
byte vA2[200] = {};
byte vA3[200] = {};

unsigned long t1, t2, t3;
void setup()
{
  if (client.connect(server, 11000))
  {
    Particle.publish("connected");
    delay(1000);
  }
  else
  {
    Particle.publish("connection failed");
  }
  setADCSampleTime(ADC_SampleTime_56Cycles);
}

void loop()
{
    t1 = millis();
  for(int i = 0; i<10; i++){
      for(int j = 0; j<100;j++){
          n = analogRead(an0);
          int k = j*2;
          vA0[k] = n & 0xFF;
          vA0[k+1] = (n >> 8) & 0xFF;
          n = analogRead(an1);
          vA1[k] = n & 0xFF;
          vA1[k+1] = (n >> 8) & 0xFF;
          n = analogRead(an2);
          vA2[k] = n & 0xFF;
          vA2[k+1] = (n >> 8) & 0xFF;
          n = analogRead(an3);
          vA3[k] = n & 0xFF;
          vA3[k+1] = (n >> 8) & 0xFF;
      }
      client.write(vA0,200);
      client.print("0<EOF>");
      delay(5);
      client.write(vA1,200);
      client.print("1<EOF>");
      delay(5);
      client.write(vA2,200);
      client.print("2<EOF>");
      delay(5);
      client.write(vA3,200);
      client.print("3<EOF>");
      delay(5);
  }
  if (!client.connected())
  {
    Particle.publish("disconnecting.");
    client.stop();
    for(;;);
  }
}

Here is a video where the adc is connected to the same signal that the osciloscope is:

The value expected in the first channel was 0 in the beggining but the data looks like its mixed with the values from the other channels.

Sorry for my bad english.

2

Can you give this code a try and check the serial output?

//SYSTEM_MODE(SEMI_AUTOMATIC);

uint8_t an[] = { A0, A1, A2, A3 };

byte vA[sizeof(an)][200];
int16_t va[sizeof(an)][100];

int16_t n;
unsigned long t1, t2, t3;

void setup()
{
  setADCSampleTime(ADC_SampleTime_56Cycles);
}

void loop()
{
  t1 = millis();
  for(int i = 0; i<10; i++) {
    for(int j = 0; j < 100; j++) {
      for(int p = 0; p<sizeof(an); p++) {
          n = analogRead(an[p]);
          vA[p][j*2+0] = n & 0xFF;
          vA[p][j*2+1] = (n >> 8) & 0xFF;
          va[p][j] = n;
      }
    }
    Serial.println("\nReadings");
    for(int p = 0; p<sizeof(an); p++) {
      Serial.printlnf("Input %d", p);
      for(int j = 0; j < 100; j++) {
        Serial.printf("%4d ", va[p][j]);
      }
    }
  }
  //while(Serial.read()<0) Particle.process();  // wait for serial input before looping
  delay(100);
}

With that code, I don’t get any kind of cross talk in the readings. Could it be that these problems don’t come from the ADC but from the way how you are transfering the data?