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Can RaceChrono use RTS/CTS with the SPP profile over Bluetooth?


I am creating a catalog get for my track bike to send GPS and RC3 strings to RaceChrono. I am wondering if I should enable the flow control SPP profile on my RN42 Bluetooth module?

I hope to connect to the Bluetooth module at 230k bps at minimum though don't know if I just push bytes as fast as possible or if the Android will use RTS/CTS to ensure its not overwhelmed.

My system is build on a 50hz GPS module and without the serial can read sensors at > 200hz. (Tensy 3.6 microcontroller based). With serial to Bluetooth it looks like 100hz is possible for RC3 output.



  • Hi Jeff,

    Any flow control is implemented in Android Bluetooth stack, and is invisible to the app developer. Also the implementation probably differs between Android versions. I think you'll need to test what works.

  • Thanks for the reply. I'll get the data working without flow control for now and then enable the flow control on the bluetooth and Teensy and see if anything changes. Once I know my data is working then I can bump up the rate or lower the baud until I see congestion and then see if flow control helps.

    Does the $RC3 data rate need to match the GPS data rate? Or can I use 2 different rates? (ie GPS @ 50 and sensors @ 100)

    Thanks, Jeff
  • Hello,

    Thought I would add an update. It looks like the Android phone API will connect to the SPP profile on the BT module with CTS/RTS if available. I have configured my RN42 with the MDM profile (SPP + RTS/CTS) and added an LED to the CTS line between the BT module and the Teensy 3.6. I can see the LED flashing.

    Also I was having problems with data issues with missing data at 230K to the BT module and 50Hz RC3 + GPS messages. I am no longer having those issues once I went to the RTS/CTS but I can't solely claim that as the solution as I also refactored some of the code in the mean time due to my other forum question where my data was not formatted correctly.

  • aolaol
    edited January 2017
    The update rate can be independent. When using the timestamps, rate can be inconstant. When using the count field the rate needs to be constant 10/20/50/100/etc hz
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