›

Multiple MetaWear R on Android

bestnamebestname
in Hardware
Hello, I would like to use the MetaWear R for prototyping.

Consider multiple MWR devices connected simultaneously, feeding the raw data into an android device via their bluetooth pairings. The number of devices is between 3 and 7.

Is this possible in the current state of the API?

With this platform, with what frequency can the MMA8452Q on the device sample?

Comments

  • LauraLaura
    hey bestname,

    Yes it is possible with the current state of the API; I would recommend streaming data at no more than 50Hz to handle that many devices.

    You also have to check on the Android documentation page to see how many devices your Android version and Android device can connect to (there could be limitations with old versions): http://developer.android.com/guide/topics/connectivity/bluetooth-le.html
     
    The MMA8452Q can sample up to 800Hz.

    The Bluetooth Low Energy (Android Smartphone <-> MetaWear) link can handle up to 100Hz of data streaming.
  • bestnamebestname
    Hi Laura,

    Thanks for the quick response. I have one more question.

    Suppose I connect only one device. I would like to transmit 800Hz data whenever the total acceleration is above some threshhold. It is fine if the data is delayed by some amount of time. Is this possible?
  • LauraLaura
    Yes it is possible.
    You can log at 800Hz for X amount of time when you reach X threshold. Please keep in mind there is a finite amount of memory and data at 800Hz will fill it quickly.
    You can send that 800Hz data log over Bluetooth at any time. 
  • bestnamebestname
    Hello,

    I have been reading about Triggers in the SDK.

    Is there any way to return the N ms of accelerometer data immediately preceding a Trigger?
  • EricEric
    No, the logger does not store data prior to a trigger being added.  You should add a trigger before starting data sampling.
This discussion has been closed.