What is the highest sample rate of the Sensortag Accelerometer?

Hi Ari,

Searching E2E for "Sensortag sampling" will turn up some suggestions in previous posts.

Also, you can refer to the datasheets for the respective sensors at www.ti.com/sensortag

Best wishes

There are a lot of posts on the subject but no real definitive answer to my question

Hello,

From BLE, you can only report at a max of 7.5ms (fastest connection interval), but the sensor may be able to achieve higher sampling. Can you explain what you are trying to accomplish? Also, were you able to access the data sheet for the Invensense.

Also, there are details in the SensorTag User Guide, available on the TI BLE wiki, on how to adjust the sensor reporting period via the GATT database / profile.

Best wishes

I'm trying to do gesture recognition and would like to know what is the highest sample rate that is supported to know If I can use TI Tag for my needs

I need sample rate of between 30-50Hz - is that possible?

user guide only talks about sample rate of magnetometer - it does not mentioned the sample rate limit on the acceleromter

Hi Ari, 

I just checked by using a CC2541 USB dongle and a Sensortag v2. In this application they limited sample rate input by a lower limit of 100ms (10hz). However you can set it by editing the example code. If you are going to retrieve the sensor data through Bluetooth, as JXS mentioned earlier, fastest connection interval of BLE is 7.5ms. 

when you say "this application" , which application are you referring to ?

which example code are you referring to ?

Thanks !

download and install ble software stack and tools from www.ti.com/.../ble-stack

You can find it in ti/simplelink/ble_cc26xx_xxxx/Projects/ble/SensorTag

In addition, you can find resources on the "Teardown" tab at www.ti.com/sensortag. Data sheets are also available at this location.

I'm told that due to the peak current strain on the coin cell battery from the MPU-9250, the sample rate was limited for this sensor. In any event, you have the full driver source code when you download the BLE-Stack V2.1

Best wishes

I tried to increase the sampling rate by changing "SENSOR_MIN_UPDATE_PERIOD" and "SENSOR_PERIOD_RESOLUTION" values.

According to the minimum connection interval (7.5ms) in theory it should be pretty easy to increase the sampling rate up to 100Hz.

but surprisingly the actual refresh rate was around 15Hz ! and it doesn't matter how high i have set the update rate.

If it is just the matter of maximum output  current on the battery, Can I surmount the limitation by changing the battery ? and How?

Hey!
I had the same issue. You need to use notifications. Sensortag firmware does not seem to be capable of packaging and sending the data within one connection interval. As a result it sends it with the next connection interval -> 7.5*2 = 15ms