How to Use ADS1292: Examples, Pinouts, and Specs

The ADS1292 is a low-power, 24-bit analog-to-digital converter (ADC) designed specifically for biopotential measurements, such as electrocardiogram (ECG) and electroencephalogram (EEG) applications. This highly integrated device includes programmable gain amplifiers (PGAs), a high-speed serial interface, and supports multiple channels for simultaneous data acquisition. Its compact design and low power consumption make it ideal for portable and wearable medical devices.

• Electrocardiogram (ECG) monitoring
• Electroencephalogram (EEG) monitoring
• Portable and wearable medical devices
• Patient monitoring systems
• Research and development in biopotential signal processing

• Resolution: 24-bit
• Number of Channels: 2 differential input channels
• Input Voltage Range: ±2.4 V (with 2.4 V reference)
• Programmable Gain Amplifier (PGA) Gains: 1, 2, 3, 4, 6, 8, 12
• Data Rate: 125 SPS to 32 kSPS
• Power Supply Voltage: 2.7 V to 5.25 V
• Power Consumption: 335 µW (at 2.4 V, 500 SPS)
• Communication Interface: SPI (Serial Peripheral Interface)
• Operating Temperature Range: -40°C to +85°C
• Package: TQFN-28 (Thin Quad Flat No-lead)

The ADS1292 comes in a 28-pin TQFN package. Below is the pin configuration and description:

1. Power Supply: Connect the analog (AVDD) and digital (DVDD) power supplies to appropriate voltage levels (e.g., 3.3 V). Ensure proper decoupling capacitors are placed near the power pins.
2. Input Signals: Connect the biopotential signals (e.g., ECG electrodes) to the differential input pins (IN1P/IN1N and IN2P/IN2N). Use proper filtering to reduce noise.
3. Reference Voltage: Use the internal reference voltage (REFOUT) or provide an external reference voltage to the REFIN pin.
4. Clock Source: Select the clock source using the CLKSEL pin. If using an external clock, connect it to the CLK pin.
5. SPI Communication: Connect the SPI pins (CS, SCLK, DIN, DOUT) to a microcontroller or processor for data acquisition and configuration.
6. Start Conversion: Use the START pin to initiate conversions. Monitor the DRDY pin to check when new data is available.

• Input Impedance: Ensure the input impedance of the biopotential signals matches the ADS1292's input characteristics to avoid signal distortion.
• Filtering: Use low-pass filters to remove high-frequency noise from the input signals.
• Grounding: Maintain a proper ground plane to minimize noise and interference.
• ESD Protection: Add ESD protection diodes to the input pins to protect the device from electrostatic discharge.
• SPI Configuration: Configure the SPI interface correctly (e.g., clock polarity and phase) to ensure reliable communication.

Below is an example of how to interface the ADS1292 with an Arduino UNO using SPI:

#include <SPI.h>

// Pin definitions
const int CS_PIN = 10;  // Chip select pin
const int DRDY_PIN = 2; // Data ready pin

void setup() {
  // Initialize SPI
  SPI.begin();
  SPI.setDataMode(SPI_MODE1); // Clock polarity and phase
  SPI.setClockDivider(SPI_CLOCK_DIV16); // Set SPI clock speed
  pinMode(CS_PIN, OUTPUT);
  pinMode(DRDY_PIN, INPUT);
  digitalWrite(CS_PIN, HIGH); // Set CS high (inactive)

  // Reset ADS1292
  resetADS1292();
  configureADS1292();
}

void loop() {
  if (digitalRead(DRDY_PIN) == LOW) { // Check if data is ready
    digitalWrite(CS_PIN, LOW); // Select ADS1292
    uint8_t data = SPI.transfer(0x00); // Read data (example)
    digitalWrite(CS_PIN, HIGH); // Deselect ADS1292
    Serial.println(data); // Print data to serial monitor
  }
}

void resetADS1292() {
  digitalWrite(CS_PIN, LOW);
  SPI.transfer(0x06); // Send RESET command
  digitalWrite(CS_PIN, HIGH);
  delay(100); // Wait for reset to complete
}

void configureADS1292() {
  digitalWrite(CS_PIN, LOW);
  SPI.transfer(0x41); // Write to CONFIG1 register
  SPI.transfer(0x02); // Set data rate to 500 SPS
  digitalWrite(CS_PIN, HIGH);
}

1. No Data Output:

   • Ensure the SPI interface is configured correctly (e.g., clock polarity and phase).
   • Verify that the START pin is asserted to begin conversions.
   • Check the DRDY pin to confirm data is ready before reading.

2. High Noise in Output:

   • Use proper filtering on the input signals to reduce noise.
   • Ensure the input signals are within the specified voltage range.
   • Verify that the ground connections are solid and free of interference.

3. Device Not Responding:

   • Check the power supply connections and ensure proper voltage levels.
   • Verify the SPI connections and ensure the CS pin is toggled correctly.
   • Reset the device using the RESET pin or RESET command.

Q: Can the ADS1292 operate with a single-ended input?
A: No, the ADS1292 is designed for differential input signals. Single-ended signals must be converted to differential using external circuitry.

Q: What is the maximum sampling rate of the ADS1292?
A: The maximum sampling rate is 32 kSPS, but lower rates can be configured for power savings.

Q: Can I use the ADS1292 with a 5 V microcontroller?
A: Yes, as long as the digital power supply (DVDD) is compatible with the microcontroller's logic levels. Use level shifters if necessary.