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CC2650STK: More information about how to read the sensor data without using SimpleLink Ti App

Harshad Lele
Prodigy 10 points
Part Number: CC2650STK
Other Parts Discussed in Thread: BLE-STACK

Tool/software:

Hi,

I am trying to read the sensor data using "python script and using Bleak library".

Here is the link:

https://github.com/hbldh/bleak

 

For now I am interested in collecting data from BMP280 (Barometer Sensor). I can get the raw data out from the sensor.

Here are my questions:

1. Are the raw data values calibrated? if not how to access the calibration values? 

2. How do I know the resolution with which I am getting the data out from BMP280?

2. From what I can tell, I am getting 6 bytes out from BMP280. From BMP280 data sheet these 6 bytes should have information of temperature and pressure values.

Based on the resolution with which BMP280 is configured, 6bytes received from sensor tag will have different meaning. How do I know the resolution with which it is configured?

3. Or can you tell the correct format with which I should parse the received raw data to make sense out of the raw data?

Note:

I have already looked at, although I believe this information will not help me answer above questions.

If it does can you please point me to the exact section in the document?

https://www.ti.com/tool/download/BLE-STACK-2-X 
https://www.ti.com/lit/tidu862 
https://www.ti.com/tool/SENSORTAG-SW 


  • 0
    TI__Mastermind 35460 points

    Hi,

    Thank you for reaching out. I would highly recommend referencing the sensortag example included in the BLE-STACK SDK as this example shows you how the data is extracted from the BMP and processed for pressure and temperature. Have you had a chance to reference the example directly?

    Best Regards,

    Jan

  • 0 in reply to Jan
    Prodigy 10 points

    Hi Jan,

    Thanks for your reply. Yes I looked at the examples.

    It is a really good reference to find the final pressure value as SensorBmp280.c explains it clearly how to find it out from the raw pressure values and calibration values.

    I can get the raw pressure values from the sensor tag over BLE using python bleak library. The final piece is the calibration values!

    Can you please guide me to the correct resource. Specifically I am looking for

    1. how to get the calibration values from BMP280 inside the sensor tag over BLE ?

    2. What is the UUID to get the calibration data from Barometer sensor inside the sensor tag?

    Any help would be much appreciated

    Thanks,

    Harshad

  • 0 in reply to Harshad Lele
    TI__Mastermind 35460 points

    Hi Harshad,

    Got it. No problem!

    Harshad Lele said:
    1. how to get the calibration values from BMP280 inside the sensor tag over BLE ?

    The calibration data may be obtained by reading the actual address that contains the calibration data in the sensor:

    The sensorBmp280Init() does it already and may be used a reference.

    To send the data over BLE, then you wil need to take this data and either send it via notification to a centra device or write it to a characteristic that the central may read.

    Harshad Lele said:
    2. What is the UUID to get the calibration data from Barometer sensor inside the sensor tag?

    I may be mistaken, but I don't recall there being a characteristic to get the calibration data by default. If this is the case, then you will need to add an additional characteristic to get it and use a custom UUID.

    Best Regards,

    Jan