How to Use AS5048 Magnetic Encoder Position Sensor: Examples, Pinouts, and Specs

The AS5048 is a high-resolution magnetic rotary encoder designed to provide precise angular position measurements. It operates by detecting the magnetic field of a rotating magnet, making it a non-contact and highly reliable solution for position sensing. With a 14-bit resolution, the AS5048 delivers accurate measurements, making it suitable for applications requiring fine angular precision. It supports both I2C and SPI communication interfaces, ensuring seamless integration into a wide range of systems.

• Robotics: Joint position sensing and motor control
• Industrial automation: Rotary position feedback for machinery
• Automotive: Steering angle and throttle position sensing
• Consumer electronics: Joystick and knob position detection
• Medical devices: Precision motion control

1. Power Supply: Connect the VDD pin to a 3.3V or 5V power source and the GND pin to ground.
2. Communication Interface: Choose between SPI or I2C based on your application:
   • For SPI, connect the CS, CLK, MISO, and MOSI pins to the corresponding pins on your microcontroller.
   • For I2C, connect the SDA and SCL pins to the microcontroller's I2C bus.
3. Magnet Placement: Place a diametrically magnetized magnet above the AS5048 sensor. Ensure the magnet is centered and within the recommended distance (1-2 mm) for optimal performance.
4. Pull-Up Resistors: For I2C mode, use pull-up resistors (typically 4.7 kΩ) on the SDA and SCL lines.

• Magnet Alignment: Ensure the magnet is properly aligned with the center of the sensor for accurate readings.
• Magnetic Field Strength: Use a magnet with a field strength between 30 mT and 70 mT.
• Decoupling Capacitor: Place a 100 nF capacitor close to the VDD and GND pins to reduce noise.
• Communication Protocol: Configure your microcontroller to match the AS5048's communication settings (e.g., SPI clock polarity and phase).

#include <SPI.h>

// Define SPI pins for AS5048
const int CS_PIN = 10; // Chip Select pin

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);

  // Configure the Chip Select pin as output
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH); // Set CS high to deselect the sensor

  // Initialize SPI communication
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV16); // Set SPI clock speed
  SPI.setDataMode(SPI_MODE1); // Clock polarity and phase
}

uint16_t readAS5048() {
  uint16_t angle = 0;

  // Select the AS5048 by setting CS low
  digitalWrite(CS_PIN, LOW);

  // Send a read command (0xFFFF) and receive the response
  uint8_t highByte = SPI.transfer(0xFF); // Send first byte
  uint8_t lowByte = SPI.transfer(0xFF);  // Send second byte

  // Deselect the AS5048 by setting CS high
  digitalWrite(CS_PIN, HIGH);

  // Combine the two bytes into a 14-bit angle value
  angle = ((highByte << 8) | lowByte) & 0x3FFF;

  return angle;
}

void loop() {
  // Read the angle from the AS5048
  uint16_t angle = readAS5048();

  // Print the angle to the serial monitor
  Serial.print("Angle: ");
  Serial.println(angle);

  delay(100); // Wait 100 ms before the next reading
}

1. No Output or Incorrect Readings:

   • Verify the power supply voltage (3.3V to 5.5V).
   • Check the magnet alignment and distance from the sensor.
   • Ensure proper connections for the selected communication interface (SPI or I2C).

2. Communication Errors:

   • For SPI, confirm the clock polarity and phase settings (SPI_MODE1).
   • For I2C, ensure pull-up resistors are present on the SDA and SCL lines.

3. Unstable Readings:

   • Add a decoupling capacitor (100 nF) near the VDD and GND pins.
   • Use a stable power supply to minimize noise.

Q: Can the AS5048 measure absolute position?
A: Yes, the AS5048 provides absolute angular position measurements with 14-bit resolution.

Q: What type of magnet should I use?
A: Use a diametrically magnetized magnet with a field strength of 30 mT to 70 mT.

Q: Can I use the AS5048 with a 3.3V microcontroller?
A: Yes, the AS5048 operates with a supply voltage range of 3.3V to 5.5V, making it compatible with 3.3V systems.

Q: How fast can the AS5048 operate?
A: The AS5048 supports rotational speeds of up to 30,000 RPM.