Unreliable Connection - Blinking Red LED

Hi there,

I have a set of 8 MetaMotionR Sensors and a MetaHub am just getting used to working with them and have a couple questions. My university has bought this set and probably put some thought into it, however put me in charge to develop some guides for our students to use the motion tracking system for their projects. I am by no means an expert in this field but am working on my engineering degree.

  1. While most sensors tend to connect and log rather reliably, one sensor can not be found by the metawear app on my android phone or windows PC, therefore making it difficult to update the firmware or running the diagnostic. I did reinstall both Metawear apps and attempted a soft reset which did not seem to work for me. This sensor is in a state where it blinks every 30 seconds. The sensor can be found by the nRF Connect and the battery is at 100%. It even sometimes does connect to my MetaHub when I run a very basic test program, that simply connects to all 8 sensors and logs data. Afterwards the blinking and connection problem however persists.

  2. I do understand that these sensors are a tool to be used within own programs and apps. Is there however any userfriendly app that can easily log and potentially graphically display sensor data within my Metahub without the need to do write my own program?

  3. I am currently in a phase where I would like to test and better understand possibilities and limitations of these sensors. One specific problem: A colleague wants to gather sensor data from ski jumpers with 8 sensors. A efficient system should be put in place as 100-1000 jumps shall be recorded.

  • I am concerned about signal range from the bluetooth for streaming. Instead logging would be okay too, but Ideally my colleague stands on top of the jump: Is it possible to start and stop the logging from there?
  • With the 8 Sensors, is it even possible to use the phone for this purpose, or is the MetaHub with the 2 Bluetooth plugin-modules required to use this many sensors.
  • The 8MB onboard memory says it can record around 500.000 entries. So If I run the accelorometers in 3 axis at 10khz. That gives me 30.000 entries per second, meaning that not much more than 15 seconds of my jump can be recorded and I need to constantly save the data from my sensors, correct?
  1. My Metawear App on my Windows 10 PC keeps crashing. Mostly when I hit add device, sometimes however right after starting it. I heard in another thread that one "faulty" sensor may have caused that issue. Maybe solution to problem 1 can solve that for me?

I am hoping I provided enough information in order to advise with some of my problems. I am not trying to let other people solve my issues, but could use a little help past these barriers to help me move on learning about the whole system. If there is any further exisiting information about these sensors out there other than the mbientlab tutorial and forum page, please feel free to forward that as well,

Best regards
Jonas

Comments

    1. It is not possible to connect to 8 sensors at once. Please clarify.
    2. The MetaBase Metahub app does this.
    3. I think you issue is that you are not following the Bluetooth and OS level parameters. This has nothing to do with our sensors but rather limitation of Bluetooth. Bluetooth can only stream up to 100Hz. This is a hard Bluetooth limitation. So you can do 1 sensor at 100Hz or 4 sensors at 25Hz.
    4. We do NOT SUPPORT WINDOWS 10! Please do not use it

    You are using Windows when we don't support it. You are using 8 sensors when only 1 or 2 are supported at once. You are going beyond the capabilities of Bluetooth. I am not surprised it does not work. AGAIN THIS IS NOTHING TO DO WITH OUR SENSORS BUT RATHER A LIMITATION OF YOUR OS AND SETUP. PLEASE READ UP ON BLE.

  • Hi Laura,

    thank you for your response! I did read up a bit more on BLE. I will try to clarify some of the points.

    1. Is it possible to setup 8 sensors to measure their data simultaneously? So triggering them somehow (Either one by one or in bundles) and having them measure data and store it locally on their own flash drive? Or what would be the easiest way to setup 8 sensors and how would you retrieve the data? In order to track body motion.
    2. Alright, thanks.
    3. So rather than sending the data via bluetooth right away, I should rather store the data locally to achieve higher data density it seems.
    4. Alright. I did however find the Metabase App in the Microsoft Store with the note under system requirements that it should have "Windows 10 or newer". A bit frustrating for your users if there is crashing Software available to them that at least seems to be coming from the manufacturers source.
    5. Referring to the mbienlab tutorials page of the metahub, it states: "You can add a Bluetooth to USB Dongle to each port to connect to more MetaSensors. Each Dongle can connect up to 4 MetaSensors at the same time." I do have 2 dongles connected to my metahub, therefore the assumption that I can connect to 8 sensors simultaniously with my MetaHub? Or am I missing something here? I understand, the data transfer is then still limited to Bluetooth's data limits.

    Also: Any insights on that one blinking sensor? Why is it behaving different to all other 7. Why the blinking?

  • edited May 31
    1. Yes but you have to do a semi custom Metahub setup.
    2. Yes, streaming tops out at 100Hz total PER BLE antenna. You can log internally at 800Hz.
    3. We are not supporting Windows at all at this time.
    4. See #1 and #3
  • Hi Laura,

    thanks again,

    1. Okay, so with the MetaHub and 2 Bluetooth Dongles I can run 8 sensors simultaniously provided I write my own code to connect to each sensor and activite the specific things I want to measure with the MetaWear software on my MetaHub.
    2. Thanks for clarifying that! So when I go to the app and for example activate the accelerometer between 12.500 and 800.000 Hz, we are actually talking 12.5 to 800 Hz, not kHz? The .xxx in Europe would indicate its in the thousands. This made me think the data rates would need to be much higher if 12.5 kHz was gonna be the lowest frequency for streaming.
    3. What about my faulty sensor? :(
      "While most sensors tend to connect and log rather reliably, one sensor can not be found by the metawear app on my android 8.0 phone, therefore making it difficult to update the firmware or run the diagnostic. I did reinstall both Metawear apps and attempted a soft reset which did not seem to work for me. This sensor is in a state where it blinks every 30 seconds. The sensor can be found by the nRF Connect and the battery is at 100%. It even sometimes does connect to my MetaHub when I run a very basic test program, that simply connects to all 8 sensors and logs data. Afterwards the blinking and connection problem however persists."
  • edited June 1
    1. It seems more applications are available for iOS than for android, correct? Might get my hands on an iPhone soon.
    2. Is it possible to transfer the logged data from the MetaMotionR sensor via cable or only via BLE? I read somewhere else, that it was planned but has it been implemented? It would be nive to accelerate it for the purpose we want to use it
  • Hey @Jonas_MCI
    1. Yes but again you have to do 4 sensors per dongle so that's 25Hz per sensor so that 4 sensors = 100Hz total per bluetooth antenna.
    2. .
    3. You are right, 12.5 to 800Hz (not KHz).
    4. .
    5. .
    6. If you have a faulty sensor let's address that separately. Since the sensor connects its not DOA but go ahead and email me at hello[at]mbientlab[dot]come and send me some info. You need to send me the issue when you try to connect it with the MetaBase/MetaWear Android or iOS App (leave all other sensors out of this entirely). Also send a diagnostic and pics.
    7. We support iOS and Android but smartphones are limited in that they don't support many connects at once. If you want to setup a lot of sensors, Linux is the way to go.
    8. The MMR works with BLE only. The MMS supports USB and BLE.

  • Hi Laura,

    thank you so much for all your advice I am understanding a lot of things better! I was finally able to connect to my "faulty" sensor and was able to update the firmware, so it seems to be running normal again now. Therefore everything is resolved for now. Thanks for getting me started!

  • Hey @Jonas_MCI,
    Welcome. Let me know if you have any other questions.
    It seemed to just be a matter of figuring out your setup / system architecture. With 8 sensors, Linux really is the way to go (smartphones have too many limitations).

Sign In or Register to comment.