How to Use AS5048A magnetic rotary encoder: Examples, Pinouts, and Specs

The AS5048A is a high-resolution magnetic rotary encoder manufactured by AM5. It is designed to provide precise angular position measurements by detecting the orientation of a magnetic field. The encoder outputs the position in a digital format, making it ideal for applications requiring accurate rotational feedback.

• Robotics: For joint position sensing and motion control.
• Motor Control: To provide feedback for brushless DC (BLDC) and stepper motors.
• Industrial Automation: For precise positioning in automated systems.
• Consumer Electronics: In devices requiring rotational input or feedback.
• Medical Devices: For applications like robotic surgery or diagnostic equipment.

The AS5048A is a versatile and robust encoder with the following key specifications:

The AS5048A comes in a TSSOP-14 package with the following pinout:

1. Power Supply: Connect the VDD pin to a 3.3V or 5.0V power source and the GND pin to ground.
2. Magnet Placement: Place a diametrically magnetized magnet (e.g., a neodymium magnet) above the encoder chip. Ensure the magnet is centered and within the recommended distance (1-2 mm).
3. Communication Interface:
   • For SPI: Connect the CSn, CLK, MISO, and MOSI pins to the corresponding SPI pins on your microcontroller.
   • For PWM: Use the PWM pin to read the angle data as a duty cycle.
4. Bypass Capacitor: Place a 100 nF ceramic capacitor close to the VDD and GND pins for power supply decoupling.

• Magnet Alignment: Ensure the magnet is properly aligned with the center of the encoder for accurate readings.
• Magnetic Field Strength: Use a magnet with a field strength between 30 mT and 70 mT for optimal performance.
• Noise Filtering: Add a low-pass filter to the PWM output if using the PWM interface.
• SPI Configuration: Configure the SPI interface with the following settings:
  • Clock polarity (CPOL): 0
  • Clock phase (CPHA): 1
  • Data order: MSB first

Below is an example of how to interface the AS5048A with an Arduino UNO using SPI:

#include <SPI.h>

// Define SPI pins for AS5048A
const int CS_PIN = 10; // Chip Select pin

void setup() {
  // Initialize Serial Monitor
  Serial.begin(9600);

  // Initialize SPI
  SPI.begin();
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH); // Set CS high to deselect the device
}

uint16_t readAngle() {
  uint16_t angle = 0;

  // Select the AS5048A
  digitalWrite(CS_PIN, LOW);

  // Send command to read angle (0xFFFF is the command for angle read)
  SPI.transfer16(0xFFFF);

  // Read the 16-bit angle data
  angle = SPI.transfer16(0x0000);

  // Deselect the AS5048A
  digitalWrite(CS_PIN, HIGH);

  // Return the angle value
  return angle & 0x3FFF; // Mask to 14 bits
}

void loop() {
  // Read the angle from the AS5048A
  uint16_t angle = readAngle();

  // Convert angle to degrees (0-360)
  float angleDegrees = (angle * 360.0) / 16384.0;

  // Print the angle to the Serial Monitor
  Serial.print("Angle: ");
  Serial.print(angleDegrees);
  Serial.println(" degrees");

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

1. No Output or Incorrect Readings:

   • Cause: Magnet misalignment or incorrect distance.
   • Solution: Ensure the magnet is centered and within 1-2 mm of the encoder.

2. SPI Communication Fails:

   • Cause: Incorrect SPI settings or wiring.
   • Solution: Verify the SPI clock polarity, phase, and connections.

3. Noisy PWM Output:

   • Cause: Electrical noise or insufficient filtering.
   • Solution: Add a low-pass filter to the PWM output.

4. Overheating:

   • Cause: Excessive current draw or incorrect power supply voltage.
   • Solution: Ensure the supply voltage is within the 3.3V to 5.0V range.

Q1: Can the AS5048A measure absolute position?
Yes, the AS5048A provides absolute angular position measurements with 14-bit resolution.

Q2: What type of magnet should I use?
Use a diametrically magnetized magnet with a field strength of 30 mT to 70 mT.

Q3: Can I use the AS5048A with a 3.3V microcontroller?
Yes, the AS5048A is compatible with both 3.3V and 5.0V systems.

Q4: What is the maximum rotational speed the AS5048A can handle?
The AS5048A can measure angles accurately at speeds up to 30,000 RPM.