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Control speed + incline using Windows PC + 4-8 channel USB HID Relay board (new: Heart Rate controlled treadmill workouts via Bluetooth Heart Rate chest band - see 2023 update below)

App icon

Github project:

Video demo of a 6-channel switch hooked up to the control panel of Kondition 4B-550 treadmill:



Relay board




  • Duration [minutes] (i.e. length of the movie you will watch during workout) Note: you can enter expressions (e.g. 24+21*3 for multiple episodes)
  • Speed - desired speed
  • Warm-up / Wind-down time [minutes] - how quickly reach desired speed
  • Sprint - maximum speed during sprint phases
  • Sprint duration [minutes] - how long the sprint period is
  • Hill - incline increase during "hill" phases
  • Reps - how many times the (hill+sprint) section repeated (with decreasing hills)
  • Start button - press again to Stop (prompt)
  • Progress - you can edit this and restart a stopped session
  • Stop button - stops the treadmill (if enabled)
  • Gear icon (upper left) - toggles settings:
    • Vidpid - entered as two hex values separted by a forward slash (/) - more info below
    • ButtonPressSec - how long the buttons need to be held down (in seconds, e.g. 0.2)
    • Channel number for each button (set it to "0" if not connected):
      • SPEED_UP, SPEED_DOWN - necessary
      • INCL_UP, INCL_DOWN - if enabled: "hill" field lets you set a repeting climb section in workout
      • START - if enabled the program will start the treadmill if progress is 0
      • STOP - if enabled: show stop button to stop the treadmill
      • MODE - if enabled: it will be pressed twice and a SPEED- before starting (this sets "infinite" time on Kondition treadmills)
      • SPD3 - if enabled: press quick button 3 instead of "manually" advancing to 3kph

Settings are saved between sessions


  • Progress [minutes] - how far into the duration
  • Next [minutes] - until the next change (speed or incline)
  • Speed - current speed (adjust treadmill if they don't match)
  • Incline - current incline (adjust treadmill if they don't match)
  • - close app (prompt if session active)
  • - keep window on top


I plan to add more, currently there is one implemented:


  • in warmup minutes increase from 3.0 to desired speed
  • slowly increase incline from 0 to hill
  • slowly decrease include from hill / 1 to 0
  • Sprint for sprint duration at sprint speed
  • slowly increase incline from 0 to half hill
  • slowly decrease incline from hill / 2 to 0
  • Sprint for sprint duration at sprint speed
  • ...repeat reps times (with decreasing hills: hill / 3, hill / 4 etc)
  • in winddown minutes decrease desired speed to 3.0
  • end of workout - end of movie

A 115 minute workout: you can see warm-up/wind-down and all the 8x3min "sprint" section's effect on the heart rate (measured using a TicWatch Pro 3 Wear OS smart watch)




The workout logic is in the function workout1:

  • dur - duration in seconds
  • p - progress
  • s - speed
  • r - incline
  • speed - desired speed
  • hl - hill
  • sp - sprint
  • warm - warmup/winddown duration between 0.1 steps (in seconds)


toggle(switch, state)

  • switch: SPEED_UP = 1, SPEED_DOWN = 2, INCL_UP = 3, INCL_DOWN = 4, ALL = 9
  • state: ON=1, OFF=0


  • it will wait 0.5 sec between ON and OFF


  • delay in seconds
  • returns true if stop was pressed

**Set your VIDPID and optional parameters **

After opening the app at least once, find the configuration file under C:\Users???\AppData\Local\walk\walk_???\\user.config

Add two settings manually (otherwise some incorrect defaults will be used):

 <?xml version="1.0" encoding="utf-8"?>
         <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System.Configuration.ConfigurationManager, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51" >
            <section name="walk.Properties.Settings" type="System.Configuration.ClientSettingsSection, System.Configuration.ConfigurationManager, Version=, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
          <setting name="Duration" serializeAs="String"><value>100</value></setting>
          <setting name="Sprint" serializeAs="String"><value>7.5</value></setting>
          <setting name="Warmup" serializeAs="String"><value>8</value></setting>
          <setting name="Speed" serializeAs="String"><value>6.2</value></setting>
          <!-- Add these optional parameters -->             
          <setting name="Vidpid" serializeAs="String"><value>0519/2018</value></setting>
          <setting name="ButtonPressSec" serializeAs="float"><value>0.2</value></setting>
          <setting name="ButtonStart" serializeAs="bool"><value>True</value></setting>
          <setting name="ButtonStop" serializeAs="bool"><value>False</value></setting>
          <setting name="ButtonMode" serializeAs="bool"><value>True</value></setting>
  • If connected program will press the MODE button and Speed- twice before starting to set 99km (=infinite) workout duration before staring (set ButtonMode to non-zero)
  • It will also press the Start button if it is also connected (set ButtonStart to non-zero)
  • The Stop on screen button will be enabled if it is connected (set ButtonStop to non-zero)
  • Set buttonPressSec according to your device. Some devices need longer button presses (e.g. 0.5 sec) to be registered, others start repeating the button if it is pressed for too long, set a lower value here (e.g. 0.2 sec)

How to find vid/pid

Get the app Hidapitester:

Use command:

hidapitester --list

Look for the id in the beginning of the line which has "HIDRelay":

0519/2018: - HIDRelay
here the vidpid is 0519/2018

Then you can open, write, close in one command.

  hidapitester --vidpid 0519 --open --send-output 0,241 --close
  output 0,241: shorts channel 1
  output 0,1: opens channel 1
  output 0,242: shorts channel 2
  output 0,249:shorts all channels
  output 0,9: opens all channels
  hidapitester --vidpid 16C0/05DF --open --send-feature 0,253,1 --close
  feature 0,255,1: shorts channel 1
  feature 0,253,1: opens channel 1
  feature 0,255,2: shorts channel 2
  feature 0,253,2: opens channel 2


  • Add more workout programs with selector
  • Make window moveable, resizable

...or not. Currently this is what I need, I provide it as a basis for anyone wanting to create something similar.

Git Hub project:

2023 update: Bluetooth Heart Rate control and more!

Heart Rate

What's new:

  • connectivity to standard Bluetooth Heart Rate sensor (e.g. Polar H9)
  • HR value displayed during workout
  • new workout program (see heart checkbox) where we can specify a lower and upper target HR, and a (maximum) time between adjustments parameter (seconds)
  • new graph showing heart rate vs. speed vs. incline (use 📊 button to show plot during workout)
  • workout screenshot and summary data is automatically saved into selected folder ("log dir path") a PNG and a TXT file is created with timestamp as filename
  • upon pressing "START" we can now turn on the treadmill via webhook using a smart switch (e.g. IFTTT or sOnOff)

Summary data example: (e.g. 2023-01-19 18.46.txt, see 2023-01-19 18.46.png above)

 Duration: 25min (warmup time: 4.1 min)
 HR Max: 124bps Avg: 103.19683bps Plot range: 85…128bps
 Speed Max: 7.00km/h Avg: 4.81km/h
 Ascend: 9946
 Distance: 1991m
 Calories: 210KCal
 Sections: (4 peaks)
  0:00:06 warmup↑100
  0:04:06 ↑115
  0:05:55 →115
  0:06:55 ↓100
  0:08:03 →100
  0:09:05 ↑115
  0:10:50 →115
  0:11:50 ↓100
  0:13:26 →100
  0:13:58 ↑115
  0:15:17 →115
  0:16:01 ↓100
  0:17:35 →100
  0:18:06 ↑115
  0:19:52 →115
  0:20:24 ↓100
  0:22:07 →100
  0:22:07 cool↓3.0

New settings:

  • BT - select bluetooth HR device (it has to be paired in Windows settings)
  • checkbox - toggle between time controlled or heart rate controlled workouts
  • TBA - time between adjustments: maximum delay [seconds] between speed / incline adjustments
  • Low - lower heart rate target
  • High - upper heart rate target
  • Lower hold - number of seconds to hold the lower heart rate level
  • Upper hold - number of seconds to hold the upper heart rate level
  • Log dir path - if specified screenshots (png) and summary text files (txt) are saved in this directory (timestamp as file name)
  • Birth date, gender, weight - needed for calorie calculation
  • HTTP on start - provide a webhook to turn on the treadmill
  • Heart rate - shows the detected HR as soon as the sensor is connected. Turns red if battery<20%. Click into field (via mouse) to re-initialize BT discovery (it will show an hourglass icon when already trying to connect to selected BTHR sensor, it will automatically retry every 15 seconds)

New, heart rate controlled workout:

  • Warm up: speed is increased every (TBA / 4) seconds until lower heart rate target is reached (store time needed and use it to make cooldown the same duration!)
  • Attempt to keep hr at this lower target value by adjusting the speed for "lower hold" number of seconds
  • Increase speed and incline (alternating) until upper heart rate target is reached ("Hill" maximum incline setting is obeyed!)
  • Attempt to keep hr at this upper target value by adjusting the speed for "upper hold" number of seconds
  • Reduce speed and incline (alterning) until lower heart rate target is reached
  • Repeat upper / lower target rates until cooldown is scheduled (same duration as it took to "warm up")
  • Summary screenshot and text file is saved when you exit the app

workout plot


  • gray vertical rules at minute marks (refreshed when duration is updated)
  • green: incline (0-15) (green tick marks at section starts)
  • blue: speed (3…8 km/h) (horizontal lines at 4,5,6,7 km/h and incline 3,6,9,12)
  • red: heart rate (automatic range adjustment) (horizontal lines at lower and upper heart rate targets)

Screenshot + Summary

  • saved automatically when Pause is pressed or end of workout or when exiting app
  • only the last screenshot is kept for the session (if saved multiple times)
  • in plot view (when settings are not visible) the screenshot has transparent background (for use in notes or website)
  • screenshot is only saved on exit if plot shows information or settings are visible

Source code notes for BT