RevPi DIO Encoder - forward counts twice as fast as moving backwards.

[daniel_123]

I am investigating the use of the RevPi DIO encoder functionality to capture position information from a quadrature encoder. During my investigations I have found that when moving forward the encoder counts at twice the rate as when moving backwards (for the same frequency signal). Is this behaviour expected? Any ideas on how I can change this?

To test encoder functionality I am using a signal generator to simulate encoder wave forms, varying the phase of these signals to simulate moving forwards and backwards.

Code to capture output data
I have also confirmed the same behaviour using piTest.

Code: Select all

import time

# Testing an input output loop, with the output 1 wire connected to input 1
# PiCtory configuration needs to be set appropriately
# with OutputValue_1 and InputValue_1 set to 0-5V
import revpimodio2

# Initialize the RevPi communication
rpi = revpimodio2.RevPiModIO(autorefresh=True)
print(rpi.cycletime)

rpi.io["Counter_3"].reset()
rpi.io["Counter_4"].reset()

rpi.io["Counter_3"].signed = True
rpi.io["Counter_4"].signed = True

time.sleep(1)

start_time = time.time()

previous_count = 0
previous_time = start_time
while True:


    time_now = time.time()
    counter1 = rpi.io["Counter_3"].value
    counter2 = rpi.io["Counter_4"].value

    print("Count3: " + str(counter1) + " Count4: " + str(counter2) +" delta: " + str(counter1 - previous_count) + " time_delta: " + str(time_now-previous_time))

    previous_count = counter1
    previous_time = time_now
    time.sleep(1)  # Sleep for 1 second

Simulated encoder signals moving backwards

Code: Select all

Count3: 35534 Count4: 0 delta: -10 time_delta: 1.000213384628296
Count3: 35524 Count4: 0 delta: -10 time_delta: 1.0002143383026123
Count3: 35513 Count4: 0 delta: -11 time_delta: 1.0002446174621582
Count3: 35503 Count4: 0 delta: -10 time_delta: 1.0002529621124268
Count3: 35492 Count4: 0 delta: -11 time_delta: 1.0002257823944092
Count3: 35482 Count4: 0 delta: -10 time_delta: 1.000220537185669

Simulated encoder signals moving forwards

Code: Select all

Count3: 35045 Count4: 0 delta: 20 time_delta: 1.0002079010009766
Count3: 35065 Count4: 0 delta: 20 time_delta: 1.0002102851867676
Count3: 35085 Count4: 0 delta: 20 time_delta: 1.0002093315124512
Count3: 35105 Count4: 0 delta: 20 time_delta: 1.000211238861084
Count3: 35125 Count4: 0 delta: 20 time_delta: 1.0002107620239258
Count3: 35145 Count4: 0 delta: 20 time_delta: 1.0002062320709229

Note that output 1 on the signal generator is plugged into DIO I4 and output 2 is plugged into I3

Device: RevPi Connect 4

Firmware version:
pi@RevPi106155:~/projects $ piTest -f
firmware is up to date: 1.5 >= 1.5

Pictory Configuration

[dirk]

Hello daniel_123, Foremost, thanks for all the information that I am still collecting, as a first idea so far - can you try to solve the problem by activating debouncing? Here is the spot in the video tutorial:
https://youtu.be/cBxmCPLKnlk?list=PLwce ... hNZu&t=329

[daniel_123]

Hi Dirk,

Thanks for your reply.

I have tried with all different debouncing settings (no debouce, 25us, 750us and 3ms) the behaviour is still the same.

Let me know if you have any other ideas.

Cheers