Wheel Encoder Counter

How to use the Wheel Encoder Counter robot skill

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This skill is compatible with Arduino UNO firmware that counts wheel rotation for left and right wheels.

Firmware

This robot skill requires supporting capability on the EZB with firmware. The firmware is open-source so that you can modify it for different Arduino's and microcontrollers. The Wheel Encoder Arduino UNO firmware can be found here: https://synthiam.com/Firmware/Wheel-Encoder-Firmware-NVXCXGPCQMJ

Main Window

1. Get Wheel Values Button Manually requests the encoder values for each wheel. Please do not use it when pushing to NMS because this is done automatically with an interval timer.

2. Reset Values Button Resets the encoder values back to zero. Please do not use it when pushing to NMS because it will break the current pose.

3. Get Wheel Values & Reset Button Resets the encoder values back to zero then starts acquiring the encoder values again. Please do not use it when pushing to NMS because this will break the pose.

4. Status Display When the debug checkbox is checked, this will display a text readout of the encoder values.

Configuration

Settings - General

1. Poll Interval How often to poll the wheel encoder values from the Arduino.

2. Display debug information This will display the wheel encoder values to the log file for debugging in real-time.

Settings - NMS

1. Push to NMS Enabling this checkbox will push the data to the NMS as a Level 3 Group 2 sensor, updating the robot's positioning pose telemetry.

2. Encoder ticks per wheel revolution How many encoder ticks for one revolution of the wheel. This is used for the NMS pose calculation if enabled.

3. Wheel diameter (mm) The diameter of the wheel is in millimeters. This value must be precise because it is important to the pose calculation. If it is off by 1 mm, it will produce errors in the calculation. If you are using a known wheel product, use the datasheet to obtain the diameter. Otherwise, there are several methods to measure a wheel diameter. This is only used for the NMS pose calculation, if enabled.

4. Pivot diameter (mm) The distance between centers of wheel treads. Similar to the wheel diameter, this is absolutely important to be as accurate as possible. If using an existing robot product, consult the datasheet to obtain the pivot diameter, which is the distance between the center of each wheel tread. This value must be accurate and not have any errors. This is used for the NMS pose calculation.

NMS

The Navigation Messaging System (NMS) is built into the ARC framework. It allows skills to push data (location & obstacle detection) into the messaging system. Then, mapping/navigation SLAM skills can subscribe to the navigation events. The NMS was designed to provide ARC users with transparent navigation. You do not have to write any complicated code because the robot skills will work for navigation and obstacle avoidance.

How to Use Wheel Encoder Counter

1. Download the Arduino firmware onto a UNO (or edit for your Arduino version). The Wheel, Encoder Arduino UNO firmware, can be found here: https://synthiam.com/Docs/Hardware/Arduino-Genuino-Uno

2. Connect your wheel encoders to ports D2 (left wheel) and D3 (right wheel) on the UNO.

3. Add the Wheel Encoder Counter Skill (Project -> Add Skill -> Navigation -> Wheel Encoder Counter). Two script variables will now be created that hold each wheel's encoder values, respectively ($LeftWheelCount & $RightWheelCount). Or, you can enable the NMS checkbox in the configuration settings to push the pose to NMS as a Level 3 Group 1 sensor.

4. Connect the UNO to ARC.

Video

Resources

The Wheel Encoder Arduino UNO firmware can be found here: https://synthiam.com/Firmware/Wheel-Encoder-Firmware-NVXCXGPCQMJ

There is a ControlCommand() to reset the $LeftWheelCount and $RightWheelCount values or force-get the values on demand rather than automatically on a timer. Do not reset or manually poll the wheel count using the NMS because it will affect the current pose data.

You can see how this skill was created by watching the live hack event here: synthiam.com/HackEvent/Dj-s-5th-Live-Hack-Session-17578

Control Commands for the Wheel Encoder Counter robot skill

There are Control Commands available for this robot skill which allows the skill to be controlled programmatically from scripts or other robot skills. These commands enable you to automate actions, respond to sensor inputs, and integrate the robot skill with other systems or custom interfaces. If you're new to the concept of Control Commands, we have a comprehensive manual available here that explains how to use them, provides examples to get you started and make the most of this powerful feature.

Control Command Manual

• controlCommand("Wheel Encoder Counter", "GetValues")
  Query the EZB firmware and get the latest encoder values. Set the values to the NMS (if checked) and populate the global variables.

  
  



• controlCommand("Wheel Encoder Counter", "GetValuesAndReset")
  Query the EZB firmware and get the latest encoder values. Set the values to the NMS (if checked) and populate the global variables, and reset the values to zero.

  
  



• controlCommand("Wheel Encoder Counter", "ResetValues")
  Reset the counter values to zero.