Quadrature decoder settings for motor encoder

RE: Quadrature decoder settings for motor encoder

ovrebekk — Tue, 27 Jul 2021 08:35:31 GMT

I see you have based your code on the SDK example.

To be honest I am not sure exactly what the SDK example is trying to show, so I made my own modified example instead:

devzone.nordicsemi.com/.../273524_5F00_qdec_5F00_simple.zip

This example sets up a simulated QDEC signal on pins 3 and 4, and configures the QDEC peripheral to use inputs 29 and 30.

Every time a new report is ready it simply prints the status of that report to the log, and lets the QDEC run continuously.

Can you give this example a go and see if it works better?

If you connect the simulated pins to the input it should report a frequency of ~200Hz, as set by the call to qdec_simulator_set(200); in main.c

If you connect your own input it should hopefully show the speed of your motor.

I moved all the QDEC parameters into the main function to make it more obvious how the QDEC is configured.

Best regards
Torbjørn

RE: Quadrature decoder settings for motor encoder

Mechatroniker — Mon, 26 Jul 2021 04:31:05 GMT

#include "includes.h"


APP_PWM_INSTANCE(motor_pwm, PWM_TIMER);


int main(void)
{

    while(1)
    {
          if(flag == 0b00000000)
          {
              initialisierung_aller_komponenten();
              initialisierung_pwm(&motor_pwm);
          }

          if(nrf_gpio_pin_read(BUTTON_CUSTOM_1) == 0 && flag == 0b00000001)
          {

              while (MOTOR_STELLUNG <= 1000)
              {
                  for (number_of_pulses=min_number_of_pulses; number_of_pulses<= max_number_of_pulses; number_of_pulses++ )
                  {
                        pulses = number_of_pulses; 
                        nrf_drv_qdec_enable();                  
                        m_report_ready_flag = false;
                        if(nrf_qdec_sample_get() == 1)
                        {
                              MOTOR_STELLUNG = MOTOR_STELLUNG + 1;
                        }
                        else if(nrf_qdec_sample_get() == (-1))
                        {
                              MOTOR_STELLUNG = MOTOR_STELLUNG - 1;
                        }
                        NRF_QDEC->TASKS_READCLRACC;
                  }
                  min_number_of_pulses  = 1;       
                  NRF_LOG_RAW_INFO("MOTOR_STELLUNG: %d \r\n", MOTOR_STELLUNG);
                  NRF_LOG_FLUSH();
              }
          }
    }
}

This is my main.c.

In the function initialisierung_aller_komponenten() are only a few settings for my other pins and the button.

void qdec_event_handler(nrf_drv_qdec_event_t event)
{
    if (event.type == NRF_QDEC_EVENT_REPORTRDY)
    {
        m_accdblread        = event.data.report.accdbl;
        m_accread           = event.data.report.acc;
        m_report_ready_flag = true;
        nrf_drv_qdec_disable();
    }
}

This is my functions_qdec.c.

RE: Quadrature decoder settings for motor encoder

ovrebekk — Fri, 23 Jul 2021 13:56:24 GMT

Are you able to share your code with me, showing how you initialize the QDEC and how the interrupts are handled?

I can make the case private if you don't want to share your code in a public case.

Best regards
Torbjørn

RE: Quadrature decoder settings for motor encoder

Mechatroniker — Fri, 23 Jul 2021 06:09:00 GMT

Hi,

yes it is an encoder with two phases which are offset by approx. 90°.

My current solution is with interrupts, I trigger the interrupt and decide in it with the help of a variable and the old encoder values in which direction the motor turns.

So it already works, I just wanted to get some more basic information about the QDEC's setting options for such an application.

RE: Quadrature decoder settings for motor encoder

ovrebekk — Wed, 21 Jul 2021 11:56:27 GMT

For clarity, when you say 'two motor encoders' it sounds like you mean two separate encoders that are independent of each other. I assume that is not the case?

The QDEC only supports one encoder that outputs two phases.

It is possible to connect these signals to GPIO interrupts instead of the QDEC, if you want to process them immediately.

It is also possible to connect the signals to a timer through the PPI controller, allowing you to measure the length of each pulse with an accuracy of 62.5ns (16MHz base timing).

Best regards
Torbjørn

RE: Quadrature decoder settings for motor encoder

Mechatroniker — Tue, 20 Jul 2021 05:21:55 GMT

Hi Torbjorn,

I have two motor encoders each with a max frequency of about 470 Hz. Because I drive the motor with a PWM this frequency changes constantly.

In the SAMPLEPER register I have currently set 1024us, but here I have also tried all other values. (with moderate success)

I have activated the debounce filter.

Is there a possibility to let the QDEC trigger not on the SAMPLEPER register but on the toggling of the inputs?

Best regards

RE: Quadrature decoder settings for motor encoder

ovrebekk — Mon, 19 Jul 2021 14:16:10 GMT

Do you know what the maximum frequency of your decoder signal will be?

What is the value of the SAMPLEPER register in the QDEC, which sets the sampling rate of the QDEC?

Have you tried to enable the debounce filter in order to handle glitches on the inputs?

Best regards
Torbjørn