ADS1299: ADS1299: Verifying Test Singal on all channels of ADS1299, waveform is showing peaks on rising and falling edge

Many thanks for the reply. I was concerned about the abnormal peaks on the rising and falling edge in the test signal.

After some testing, I encountered a slightly different problem. When I increase the sampling rate, the test data on the channels starts showing garbage. For example, at 250 samples per second, all channels are correct. However, at 1k samples per second, I find that the last 3 channels show garbage data, as shown below. At the maximum speed of 16k samples per second, all channels display garbage.

The last 3 plots are channel-6,7,8 and first plot is channel 1-5.

Similarly when i set 16K samples in config-1, all the plots are showing garbage data:

After many trials, I decided to perform a test. The code below is used to read 2000 samples of data from all channels. The sampling rate is increased by one step and sent via the serial port. I used a serial datalogger to record the data. However, I observed that as I increase the sampling rate, I am unable to record the data. I have included the plots of the data as well as my logic to read and print the data. Please review it and guide me on what changes should be made to read and print data at maximum speed.

Serial baudrate: (230400);

CODE To read 2000 data samples from all channels and increasing sampling rate:

for (uint8_t regValue = 0xD6; regValue >= 0xD0; regValue--) 
      {
        digitalWrite(ledPin, LOW);
        sendCommand(ADS1299_SDATAC);
        writeRegister(ADS1299_CONFIG1, regValue);

        // Print the current register value to the Serial Monitor
        Serial.print("Config1 Data: 0x");
        Serial.println(regValue, HEX);  // Prints the current register value in HEX
        startDataAcquisition();
        lastSampleTime = millis();
        sampleCount = 0;
          while (sampleCount < 2000)
          {
            if (digitalRead(ADS1299_DRDY_PIN) == LOW) 
            {
              readAndPrintData();
              sampleCount++;
            }
          }

          stopDataAcquisition();
          sendCommand(ADS1299_SDATAC);
          delay(10);

      }

This is my read and print function code:

void readAndPrintData() 
{
  digitalWrite(ADS1299_CS_PIN, LOW);
  
  // Skip status bytes (3 bytes)
  for (int i = 0; i < 3; i++) {
    SPI.transfer(0x00);
  }

  // Read and print channel data
  for (int i = 0; i < numChannels; i++) {
    long channelData = 0;
    for (int j = 0; j < 3; j++) {
      channelData <<= 8;
      channelData |= SPI.transfer(0x00);
    }
    
    // Handle negative values
    if (channelData & 0x800000) {
      channelData |= 0xFF000000;
    }
    
    // Convert to microvolts
    float microvolts = (float)channelData * (4.5 / 0x7FFFFF) * 1000000.0 / 1.0; // Assuming gain = 1
    Serial.print(microvolts, 2);
    if (i < numChannels - 1) Serial.print(",");
  }
  Serial.println();

  digitalWrite(ADS1299_CS_PIN, HIGH);
}

My start data/stop data functions:

void startDataAcquisition()
{
  sendCommand(ADS1299_START);
  delay(10);
  sendCommand(ADS1299_RDATAC);  // Enter read data continuous mode
  delay(10);
}

void stopDataAcquisition()
{
  sendCommand(ADS1299_STOP);
  delay(10);
}

Here are data plots:

The code is run multiple times to record 2000 samples and change value of CONFIG-1 and then recordnprint using the same function...

SORRY for long post but need help.

May thanks