Go Down

Topic: Reading two quadrature encoders using Encoder.h library (Read 274 times) previous topic - next topic

01Tester01

Hi!

I'm running into a problem right now with a project I'm working on.

I have to control the position of 2 DC motors and therefore have attached an encoder (HEDM-5500) with 1000 counts per revolution to each one of them.

I'm running my motor control loop at 1kHz (Timer interrupt), where I generate my position setpoint, handle the PID calculation and measure some data with the ADC.

If I'm only ever reading one of the encoders using the Encoder library from Paul Stoffregen everything works fine, but If I start to control both motors and therefore read both encoder values one of the starts to temporarily not count steps.

I think I'm running into a problem with the interrupts not being called, but I don't know.

My PID calculation stuff is definitely fast enough, it takes at max. 750 µs out of the 1000 µs available, but even if I lower the control loop frequency and therefore give the system more idle time nothing changes with the encoder behaviour.

I hope someone can help me out with my problem.

ard_newbie

You could consider using the 2 hardware quadrature decoders of the DUE. They are capable of handling a very high number of encoder edges per second.

The Arduino DUE has two hardware quadrature decoder QDEC0 and QDEC1

QDEC0:
Timer Counter 0 channel 0 / TIOA and TIOB of channel 0
PHA  TIOA0 = pin 2
PHB  TIOB0 = pin 13
Timer Counter 0 channel 1 / TIOB of channel 1
INDEX  TIOB1 = pin A6

QDEC1:
Timer Counter 2 channel 0 / TIOA and TIOB of channel 0
PHA  TIOA6 = pin 5
PHB  TIOB6 = pin 4
Timer Counter 2 channel 1 / TIOB of channel 1
INDEX  TIOB7 = pin 10

For example sketches to record position or speed (from reply 84):
https://forum.arduino.cc/index.php?topic=140205.75


01Tester01

I have tried the hardware quadrature decoder, but was only successful with the one on TC0, additionally I was not yet able to properly reset the counter whenever I want to.

Have you tried "resetting" the output register before?

ard_newbie

I have tried the hardware quadrature decoder, but was only successful with the one on TC0
Why ?

Go Up