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Sensemore Infinity BLE Protocol Usage

Sensemore Infinity is a vibration and temperature sensor which communicates with BLE protocol. You can interact with Sensemore Infinity by using following BLE protocol details. When you send a measurement request to the Sensemore Infinity, it measures data and stores it into internat storage, after that you can read data and process in your environment. Sensemore works with battery, if you want to have maximum battery life you can also sleep device for a period of time. Measurement data contains three axial accelerometer data. Data parsing will be detailed in the following sections.

Scan

In order to connect Sensemore Infinity you should scan for BLE devices first. We try our best to keep battery life longer so Sensemore Infinity sends advertising packets a little less often than usual. If you cant find the device in the first scan, consider increasing scan timeout.

Connect

Bonding is disabled in Sensemore Infinity devices. You only need to connect to the device to take measurements. Sensemore Infinity is battery powered sensor. Staying connected for too long can cause the battery level to drop quickly. In order to increase battery life we can sleep Sensemore device. We will be discuss it the following sections.

Configuration

Sensemore Infinity stores configuration inside and takes measurement according to the configuration.

There are three types of configuration

  • Sampling Rate
  • Samplie Size
  • Accelerometer Range

Writing Sampling Rate

  • Operation Write Characteristic
  • Characteristic 55e9c0c3-1943-42ad-8b77-d33d1dee81e8
  • Datatype uint16
  • Unit index

SamplingRate configuration is done by writing the Sampling Rate Index value to 55e9c0c3-1943-42ad-8b77-d33d1dee81e8 characterisric. Using the frequency values could yield to incorrect results. We will discuss about calibrated sampling rate in the following sections.

You can also read this characteristic to learn which value is written before.

Sampling Rate Index Frequency
5 ~800Hz
6 ~1600Hz
7 ~3200Hz
8 ~6400Hz
9 ~12800Hz
10 ~25600Hz

Writing Sample Size

  • Operation Write Characteristic
  • Characteristic 2a690bfd-9b2c-4011-875c-8be2637c8f0b
  • Datatype uint32
  • Unit number of samples

Sample Size configuration is done by writing the number of samples to 2a690bfd-9b2c-4011-875c-8be2637c8f0b characterisric. Sensemore Infinity will be using this value to stop measuring. Measurement time will vary according to the configuration of sample size and sampling rate.

Although Sensemore Infinity could measure up to 500K sample it is not advised to use because transmitting the measurement data could take up to half hour.

You can also read this characteristic to learn which value is written before.

Writing Accelerometer Range

  • Operation Write Characteristic
  • Characteristic e6b5fbf8-00a6-4770-8888-626fb73e0ba4
  • Datatype uint8
  • Unit index

Accelerometer configuration is done by writing the Accelerometer Range Index value to e6b5fbf8-00a6-4770-8888-626fb73e0ba4 characterisric. Using the range value will be discussed in the measurement section.

You can also read this characteristic to learn which value is written before.

Accelerometer Range Index Range range*2/2^16
1 2 0.000061
2 4 0.000122
3 8 0.000244
4 16 0.000488

Measurement

After writing neccessary configuration values, device will be ready to take measurements.

Taking a measurements consist of two steps. Starting a measurement and reading the measurement. Sensemore Infinity stores data into its internal flash while measuring.

You do not have to configure device for each measurement. Sensemore Infinity will use the previous configuration values to take measurements. You can also read back the configuration values and the data anytime you want.

Starting Measurement

  • Operation Indication
  • Characteristic e6b5fbf8-00a6-4770-8888-626fb73e0ba4

You can start a measurement when every you want. Sensemore Infinity will be using the configuration stored inside. When you start an indication to characteristic e6b5fbf8-00a6-4770-8888-626fb73e0ba4 Sensemore Infinity first remove neccessary space in the internalflash then starts sampling the data and storing into its internal flash After measurement is done successfully, Sensemore Infinity sends a random byte through indication then indication can be closed safely.

Reading Measurement

  • Operation Indication
  • Characteristic 552bfd36-8a69-42d1-b6ce-e1c0ea2137ef
  • DataType int16 array

If sensor is idle you can start reading anytime you want. You can handle payloads and interpret as int16 array, after receiving all payloads you can safely close the indication.

Parsing payloads

Each payload consist of three axial samples and each samples data type is int16. It has the following representation.

Representation of the measurement package via accelerometer axis data:

X1 Y1 Z1 X2 Y2 Z2 ... X40 Y40 Z40
2byte 2byte 2byte 2byte 2byte 2byte ... 2byte 2byte 2byte

Example

Let's take a measurement of 8 samples with the 2G accelerometer range.
The correction coefficient of 2G is 0.000061
8 -> 8 * 3(for each axis) = 24 total samples
Each sample is represented by int16: 2 * 24 = 48 bytes for the sake of simplicity we assume each ble payload is 32 bytes. Then you now you can close the indication after receiving 32 bytes. You can parse the payloads while reading the indication also. In this examples, we assume that we collect data and store into a buffer then process it later.
Here is the ble payloads:

Payload Data
payload0 b1 fc a8 43 60 04 a8 fc a9 43 2c 04 c3 fc b2 43
payload1 21 04 99 fc f0 43 35 04 d5 fc a2 43 41 04 c6 fc
payload2 a0 43 46 04 b7 fc f1 43 03 04 b1 fc 94 43 04 04
Merged Bytes b1 fc a8 43 60 04 a8 fc a9 43 2c 04 c3 fc b2 43 21 04 99 fc f0 43 35 04 d5 fc a2 43 41 04 c6 fc a0 43 46 04 b7 fc f1 43 03 04 b1 fc 94 43 04 04
Int16 representation -847 17320 1120 -856 17321 1068 -829 17330 1057 -871 17392 1077 -811 17314 1089 -826 17312 1094 -841 17393 1027 -847 17300 1028
Accelerometer Range Corrected(2G) 0.051667 1.05652 0.06832 -0.052216 1.056581 0.065148 -0.050569 1.05713 0.064477 -0.053131 1.060912 0.065697 -0.049471 1.056154 0.066429 -0.050386 1.056032 0.066734 -0.051301 1.060973 0.062647 -0.051667 1.0553 0.062708
X -0.051667 -0.052216 -0.050569 -0.053131 -0.049471 -0.050386 -0.051301 -0.051667
Y 1.05652 1.056581 1.05713 1.060912 1.056154 1.056032 1.060973 1.0553
Z 0.06832 0.065148 0.064477 0.065697 0.066429 0.066734 0.062647 0.062708

You can use following java code to parse bytes[2] to int16: ((bytes[1] << 0) & 0x00ff | (bytes[0] << 8) & 0x7f00);

Reading Battery Level

  • Operation Read Characteristic
  • Characteristic 191341a6-3640-4dd7-9705-d7d02268ba81
  • Datatype uint16
  • Unit mV In order to calculate voltage value, you should divide the result by 1000

Reading Temperature

  • Operation Read Characteristic
  • Characteristic 14afd82c-6a1c-4eb5-ab73-ea2afc64153b
  • Datatype uint16
  • Unit 1000 * Celcius

In order to calculate celcius value, you should divide the result by 1000

Reading Calibrated Sampling Rate

  • Operation Read Characteristic
  • Characteristic 2c15e29a-0630-420f-a409-ad569b943068"
  • Datatype uint32
  • Unit Hz

Sensemore Infinity calculates calibrated sampling rate on the fly, after each measurement you should ask for last calibrated sampling rate and use it for further calculations.

Reading Magnetometer Data

  • Operation Indication
  • Characteristic 1028b182-5110-4c53-b0e4-06f6999d2ede
  • Datatype int16 * 3 axis

Magnetometer is running sync with accelerometer measurement so it doesnt require any configuration. You can read magnetometer data after successfull measurement any time.

Sample Size and Sampling Rate

While magnetometer is running sync with accelerometer, sample size and sampling rate is calculated accordingly. Following table shows the conversion rate with respect to accelerometer sampling rate.

Selected Sampling Rate Conversion Rate
800 1
1600 2
3200 4
6400 8
12800 16
25600 32

You can read up to 4096 sample for each axis of magnetometer.

MAX_MAGNETOMETER_SAMPLE_SIZE 4096
Magnetometer
Sample Size		 MIN(Accelerometer Sample Size / Conversion Rate,4096)
Magnetometer
Sampling Rate		 Accelerometer Calibrated Sampling Rate / Conversion Rate

Example Calculations

Accelerometer Magnetometer
Selected
Sampling Rate		 Selected
Sample Size		 Calibrated
Sampling rate		 Conversion
Rate		 Sampling Rate Sample Size
800 1000 846 1 846 1000
1600 3000 1678 2 839 1500
3200 5000 3342 4 835 1250
6400 10000 6489 8 811 1250
12800 20000 13327 16 832 1250
25600 30000 26674 32 833 937
800 25000 846 1 846 4096
1600 25000 1678 2 839 4096
3200 25000 3342 4 835 4096
6400 50000 6489 16 405 3125
12800 50000 13327 32 416 1562
25600 50000 26674 64 416 781

Parsing Magnetometer

Magnetometer is also provide 3 axial values. Data parsing is also similar to accelerometer. Each payload consist of three axial samples and each samples data type is int16. It has the following representation.

Representation of the measurement package via accelerometer axis data:

X1 Y1 Z1 X2 Y2 Z2 ... X40 Y40 Z40
2byte 2byte 2byte 2byte 2byte 2byte ... 2byte 2byte 2byte

Sleep

  • Operation Write Characteristic
  • Characteristic f3b67640-58f3-436f-a8a8-240400eed98f
  • Datatype uint32
  • Unit Seconds

The Sensemore Infinity battery offers up to a week of battery life without being put to sleep under normal conditions. For long-lasting use, the Sensemore Infinity device can be put to sleep when it is not taking measurements, and the battery life can be increased up to 6 months.

For t he sake of the optimisation sleep durations should be power of two. If you use different value it ceil value to the next power of two.

You can find valid values imn the tables below

Seconds Minutes Hours
4 0.066666666666667 0.001111111111111
8 0.133333333333333 0.002222222222222
16 0.266666666666667 0.004444444444444
32 0.533333333333333 0.008888888888889
64 1.06666666666667 0.017777777777778
128 2.13333333333333 0.035555555555556
256 4.26666666666667 0.071111111111111
512 8.53333333333333 0.142222222222222
1024 17.0666666666667 0.284444444444444
2048 34.1333333333333 0.568888888888889
4096 68.2666666666667 1.13777777777778
8192 136.533333333333 2.27555555555556
16384 273.066666666667 4.55111111111111
32768 546.133333333333 9.10222222222222
65536 1092.26666666667 18.2044444444444
131072 2184.53333333333 36.4088888888889