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19 June 2022

Cycplus Reliability Issue

by Stuart Lynne

The Cycplus Ant+ dongle does not cope with multiple Ant+ devices. This makes it unreliable for collecting data.

The Fitness_Dashboard program can use the Cycplus, and will automatically reset when an error is encountered, but there is a short (4-8 seconds) delay where data will be lost.


This can be tested easily with the Fitness_Dashboard and three heart rate monitors. Just wear three heart rate monitors and run Fitness_Dashboard with the Cycplus dongle plugged in.

You can then monitor the Fitness/logs/ant.log file (if you have bash, tail -f ant.log).

Typically after a few minutes you will see a reset.

Trace Example

This is a typical sequence of the Cycplus failure under load, when stops responding at the USB layer to IN transactions.

Cycplus USB Trace Example

Fortunately this error is reported up the USB stack so that the device can be reset.

Errors observed with Cycplus Ant+ Dongle.

This is a typical sequence of the Cycplus failure under load, when stops responding at the USB layer to IN transactions. This requires that the entire Ant+/USB stack be stopped, reset, and restarted.

WARNING | TOTAL MESSAGES:      644       1280
WARNING | ALLOWED: HRM-18877:  220        428
WARNING | ALLOWED: HRM-28525:  210        422
WARNING | ALLOWED: HRM-42396:  226        430
WARNING | TOTAL MESSAGES:      656       1936
  ERROR | USBError e.errno: 5 e.backend_error_code: -1 probably no such device, STOPPING
WARNING | AntIO stopped
WARNING | Ant App stopping AntState
WARNING | Driver stopped
WARNING | AntIO stopped
WARNING | Ant App stopping USB
WARNING | Ant App Closed
   INFO | Manufacturer: CYCPLUS
   INFO | Product: ANT USBStick2
   INFO | idVendor: 0x0fcf
   INFO | idProduct: 0x1008
   INFO | Driver
WARNING | Ant App starting AntState
   INFO | USBReadLoop
WARNING | Reset initiated
WARNING | INITIAL SEND[1]: TX_POWER | 0x47 | 00 FF| txPower: ff
   INFO | SEND[06]: a4 02 47 00 ff 1e
   INFO | RECV[07]: a4 03 40 00 47 00 a0
   INFO | SEND[05]: a4 01 4a 00 ef
   INFO | RECV[05]: a4 01 6f 20 ea

Ant Log

Complete ant.log for this test.

Cycplus ant.log example


There was some discussion in the Tacx knowledge base about Cycplus.

ANT+: What the FAQ Cycplus ANT+ Stick

Cycplus Contact

This was a response generated from Cycplus two years ago.

Steven zhou
2 years ago
I am steven. I am a R&D Engineer from CYCPLUS team.
Thanks for your support.
Because Nordic and Garmin will stop selling the IC(Nrf24ap2) for designing USB ant stick. So we have to change the solution. There are some bug in these products we sold from 10/2019 to 02/202. You can’t ues ERG noemolly. We have solved the problem from now.
Please contact me if you have the problem about ERG.
My email is
We will send a new one to you for free.
So sorry for our mistake in work.
We will design more better and affordable products for you in the fulture.
Thanks you.

I recently contacted Cycplus referring to the above message, with two questions:

  1. Can I get a known good Cycplus (i.e. what is referred to above)
  2. For any Cycplus dongle, is there a way to determine if it is the older (unreliable) or newer (hopefully reliable) version

This is the final response:

from:	Cycplus Support <>
to:	stuart lynne <>
date:	Jun 7, 2022, 7:57 PM
subject:	Re: Re: Cycplus Ant+ Dongle
Unfortunately, I cannot confirm if we can send you a couple of Cycplus Ant+ dongles that are known to be good. I will forward your request to my boss, thanks.

Best Regards,
Cycplus Support Steven