Metamotion R Logging Filtered Data

I'm logging using a periodicsample filter:

MBLFilter<MBLQuaternionData *> *quaternionFilter = [_device.sensorFusion.quaternion periodicSampleOfEvent:250];
[[quaternionFilter startLoggingAsync];

However I'm wondering how I might go about downloading the log if I can't persist a reference to the filter.  It works if the app continues to run, and I keep a reference to the filter and use that to download the logs:

[[_quaternionFilter downloadLogAndStopLoggingAsync:YES progressHandler:^(float number)...

However I can't really do that if I set the device to start logging, and then at some point later I want to download the data after the app has closed and re-opened. Is there a way to enumerate the active filters for an object, or retrieve it somehow?
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Comments

  • See this post on the tutorials page.  It was written a while ago but I believe everything is still good for iOS api v2.8.3.

    Also see the Gotchas section for the MBLEvent documentation:
  • Ah thank you! exactly what I was looking for
  • Hello,
    I am trying to do something similar, but using the Swift API. I am currently using the develop branch 2.8.3, because 2.8.2 asserts when trying to periodicSample the sensor fusion quaternion data. I am using the following code to start logging periodically and then I receive an assertion when trying to stop logging.

    let filter = sensorNetwork?.getSensor(loc: .leftLower)?.sensorFusion?.quaternion.periodicSample(ofEvent: 200);
    filter?.startLoggingAsync();
    filter?.downloadLogAndStopLoggingAsync(true);

    And this is the assertion error I receive,
    Assertion failed: (self.activateCount >= 0), function -[MBLRegister deactivateAsync]_block_invoke

    Do you know if there is anything I can do to fix this? Thanks for your help.
  • Can you successfully log quaternions as is without using a filter?
  • edited May 5
    Yes, I am able to begin and stop logging unfiltered quaternions. I have noticed that my timestamps are not correct but the quaternion readings are correct. 
    I have also noticed that if I attempt to begin logging data on the same sensor twice without first stopping it logging, I get the assertion as well:
    Assertion failed: (self.activateCount >= 0), function -[MBLRegister deactivateAsync]_block_invoke
  • edited May 5
    Riley, here is my obj-c code if it helps: (I'm using 2.8.3 dev branch of the api, needed for quaternion filtering, as you said)


    //-------------------------QuaternionConfig.h-------------------------//
    (implements MBLRestorable for the runOnDeviceBoot method, the NSCoding method implementations shown in the tutorial Eric posted are no longer needed as FastCoding is now used to code all properties)
    #import <Foundation/Foundation.h>
    #import <MetaWear/MetaWear.h>

    #define SAMPLE_INTERVAL 0.25

    @interface QuaternionConfig : NSObject <MBLRestorable>
    @property (nonatomic, strong) MBLEvent *filteredQuaternion;


    //-------------------------QuaternionConfig.m-------------------------//
    #import "QuaternionConfig.h"

    @implementation QuaternionConfig
    -(void)runOnDeviceBoot:(MBLMetaWear *)device{
        //configure quaternion
        device.sensorFusion.mode = MBLSensorFusionModeNDoF;
        self.filteredQuaternion = [device.sensorFusion.quaternion periodicSampleOfEvent:SAMPLE_INTERVAL*1000];
        [self.filteredQuaternion startLoggingAsync];
    }
  • edited May 5
    //-------------------------Code to start logging-------------------------//
    (Note: this restarts the Metawear sensor with the defined config and starts logging as per the runOnDeviceBoot method in QuaternionConfig class)
    [metawearDevice setConfigurationAsync:[[QuaternionConfig alloc] init]];



    //---------------Code to stop and download logging---------------// 
    (this will work even after a restart of the app)
    QuaternionConfig *qConfig = metawearDevice.configuration;
    [qConfig.filteredQuaternion downloadLogAndStopLoggingAsync:YES ....

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