Get the data from ODrive continuously

Support
#1

Hi,there.

I am not very good at English, so I apologize in advance.

Now, I use Arduino to get the data from ODrive and output the data to Serial Monitor (Arduino IDE).
But, this way couses time delay. ( I need to send command from Arduino to ODrive at very short intervals(10Hz))

Is there any good way?

Thanks.

#2

I’m surprised that you are having problems at 10Hz. This should be easily achievable by any of the ODrive’s many control interfaces.
The most common approach us to use serial, a more advanced approach is to use CAN. If you have a computer or Raspberry Pi, you can use USB and Python of course.

#3

Below code is a part of my Arduino code

if (c == 't') {
    Serial.println("Executing test move");
    for (float ph = 0.0f; ph < 6.28318530718f * 50; ph += 0.63f) {
    time = millis();
    
    float pos_m0 = 1.0f * sin(ph);
    odrive.SetCurrent(0, pos_m0); 
    // diplay serial monitor 
    odrive_serial  << "r axis" << 0 << ".controller.input_torque"
    Serial << odrive.readFloat() << '\t';
    odrive_serial  << "r axis" << 0 << ".motor.current_control.Iq_measured"
    Serial << odrive.readFloat()  * k << '\n'; // k is torque constant
  }
}

Because for loop takes 2 ms in one cycle I adjust ph value and achive 10Hz.
However, motor does not rotate smoothly. (If “odrive_serial << ~” statement is commented out, motor rotate smoothly.)

What’s wrong with my program?

Thanks.

#4

A few suggestions:
1: Increase your serial port Baud rate as high as it will go without errors. If you are at 9600 baud, it could explain why it is going so slowly.
2: Use something to limit the loop rate. e.g. define a total time and a loop rate, and a number of steps = total_time * loop_rate, and then wait until time >= start_time + (step_n/total_steps) * total_time. That way you will not saturate the communications link.
3: If it is still too slow, consider using the native protocol over serial.

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