TMC2208 Overview

Connections & Pin Functions

The module uses a StepStick-style two-row header arrangement, but physical orientation must be checked against the labels on the actual module and the socket it is being installed into. Never insert the module only by comparing component positions with an A4988, DRV8825 or another TMC carrier.

Standalone Microstep Selection

Arduino UNO Wiring – Standalone STEP/DIR Test

This test does not require a library or UART connection. Use a separate motor power supply suitable for the stepper motor. A 12V supply is convenient for many bench tests, but the correct supply depends on the complete motor and motion-control system.

Supply Decoupling

For a standalone bench setup, fit a low-ESR electrolytic capacitor of at least 100µF between VM and GND close to the driver. A 3D-printer or CNC controller board may already provide suitable bulk capacitance near its driver sockets.

Setting the Motor Current

The onboard potentiometer controls the analogue VREF setting when the TMC2208 is being used in its normal standalone analogue-current mode. Current must be adjusted for the connected motor rather than simply turning the potentiometer to its maximum position.

The module shown for this product has current-sense resistors marked R110, indicating nominal 0.11Ω sense resistors. If the markings on the module you receive are different, use the values on that module rather than assuming 0.11Ω.

Recommended Setup Procedure

1. Check the motor manufacturer’s rated phase current.
2. Install the heatsink and arrange airflow before extended operation.
3. Switch motor power off before connecting the motor or moving the driver.
4. Start with a conservative current setting rather than maximum adjustment.
5. If a labelled VREF test point is available, measure VREF relative to GND while carefully adjusting the potentiometer with an insulated tool.
6. If the carrier has no documented VREF test point or current conversion, use a verified UART current setting instead of guessing a VREF formula.
7. During initial testing, check both the motor and driver temperature and increase current only when the application requires more torque.

Arduino STEP/DIR Proof-of-Operation

No additional Arduino library is required for this basic test. Upload the sketch after checking the motor coil pairs and setting a conservative motor current.

const byte EN_PIN   = 7;
const byte DIR_PIN  = 8;
const byte STEP_PIN = 9;

void moveSteps(unsigned long steps, bool direction) {
  digitalWrite(DIR_PIN, direction);
  delayMicroseconds(10);

  for (unsigned long i = 0; i < steps; i++) {
    digitalWrite(STEP_PIN, HIGH);
    delayMicroseconds(500);
    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(500);
  }
}

void setup() {
  pinMode(EN_PIN, OUTPUT);
  pinMode(DIR_PIN, OUTPUT);
  pinMode(STEP_PIN, OUTPUT);

  // Keep the driver disabled while outputs are initialised.
  digitalWrite(EN_PIN, HIGH);
  digitalWrite(DIR_PIN, LOW);
  digitalWrite(STEP_PIN, LOW);

  delay(100);

  // EN is active LOW.
  digitalWrite(EN_PIN, LOW);
}

void loop() {
  moveSteps(800, LOW);
  delay(750);

  moveSteps(800, HIGH);
  delay(1500);
}

Expected Result

The motor should rotate smoothly in one direction, pause, then rotate back in the opposite direction. The exact angle travelled depends on the motor’s full-step count and the selected microstep resolution.

If the motor vibrates without rotating, switch off power and re-check that each output pair is connected to one complete motor winding. If it turns in the opposite physical direction to the one required by your mechanism, reverse the DIR setting in software or swap both wires of one motor winding while power is off.

Optional UART Configuration

UART is not required for ordinary STEP/DIR operation. It is useful when firmware needs to configure motor current, microstepping, chopper behaviour or read diagnostic information.

Arduino Library

In the Arduino IDE, open Library Manager, search for TMCStepper by Teemu Mäntykallio and install it before compiling the UART example.

Single-Wire UART Connection

For bidirectional UART, the TMC2208 uses the same PDN_UART line for transmit and receive. A common microcontroller connection uses the receive pin directly and feeds the transmit signal through a 1kΩ series resistor.

The following example assumes the module has R110 / 0.11Ω sense resistors as shown on the product module. Check your module before using this value.

#include <TMCStepper.h>

const byte SW_RX    = 4;
const byte SW_TX    = 5;
const byte EN_PIN   = 7;
const byte DIR_PIN  = 8;
const byte STEP_PIN = 9;

constexpr float R_SENSE = 0.11f;

// Start conservatively and change this to suit the motor.
// TMCStepper specifies rms_current() in milliamps RMS.
const uint16_t MOTOR_CURRENT_MA = 400;

TMC2208Stepper driver(SW_RX, SW_TX, R_SENSE);

void moveSteps(unsigned long steps, bool direction) {
  digitalWrite(DIR_PIN, direction);
  delayMicroseconds(10);

  for (unsigned long i = 0; i < steps; i++) {
    digitalWrite(STEP_PIN, HIGH);
    delayMicroseconds(500);
    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(500);
  }
}

void setup() {
  Serial.begin(115200);

  pinMode(EN_PIN, OUTPUT);
  pinMode(DIR_PIN, OUTPUT);
  pinMode(STEP_PIN, OUTPUT);

  digitalWrite(EN_PIN, HIGH);
  digitalWrite(STEP_PIN, LOW);
  digitalWrite(DIR_PIN, LOW);

  driver.begin();

  // Configure PDN_UART for UART operation.
  driver.pdn_disable(true);

  // Use register-controlled current rather than the analogue VREF input.
  driver.I_scale_analog(false);

  driver.rms_current(MOTOR_CURRENT_MA);
  driver.microsteps(16);
  driver.pwm_autoscale(true);
  driver.toff(3);

  uint8_t result = driver.test_connection();

  if (result == 0) {
    Serial.println("TMC2208 UART connection OK");
    digitalWrite(EN_PIN, LOW);
  } else {
    Serial.print("TMC2208 UART connection failed, code ");
    Serial.println(result);
    digitalWrite(EN_PIN, HIGH);
  }
}

void loop() {
  if (driver.test_connection() != 0) {
    digitalWrite(EN_PIN, HIGH);
    delay(1000);
    return;
  }

  moveSteps(800, LOW);
  delay(750);

  moveSteps(800, HIGH);
  delay(1500);
}

Expected UART Result

Open the Serial Monitor at 115200 baud. A successful bidirectional connection should display TMC2208 UART connection OK, after which the motor should move backwards and forwards.

If the UART check fails but ordinary STEP/DIR operation works, concentrate on the PDN_UART route, solder jumper or UART wiring rather than the motor outputs.

Power, Cooling & Installation

Troubleshooting