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Sensortag 2 battery life

Adrian Cox56
Prodigy 170 points
Other Parts Discussed in Thread: CC2650, CC2640

Hi,

I have created a simple beacon application based on the peripheral sample.  It broadcasts data every 500ms at 0Db TX power.  

The battery lasts for just 4-5 days, this seems very short. 

I don't have any equipment to monitor the current consumption but is the length of battery life as expected for the broadcast settings I'm using?

If it isn't, what can I do to extend it?

Thanks

Adrian

  • 0
    TI__Guru** 106705 points
    Hi Adrian,

    You really need something to measure the current consumption, a multi meter will do. You have to ensure that there is nothing else drawing current on your board. Are all sensors in sleep mode for example?

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    Prodigy 170 points

    Hi Fredrik,

    I'll sort out a multimeter today.

    I assumed that the sensors would not be on if I was no longer using the sensortag code, is that not the case? 

    Thanks
    Adrian

  • 0 in reply to Adrian Cox56
    TI__Mastermind 29650 points

    Adrian,

    Many digital sensor power up in some kind of normal operation mode and you will need to set them in a low power mode after boot.

    Looking at the SensorTag schematic (http://www.ti.com/tool/cc2650stk#Technical Documents) several peripherals will draw current:

    • Buzzer might draw some current (very little) if buzzer pin is not set low
    • External flash
    • Pressure sensor
    • Infrared sensor
    • Light sensor 
    • Humidity sensor

    If you do not want to include code to power down these then you might need to de-solder the sensors and make sure you have no floating input pins to the CC2650 causing a current leak.

    Regards,
    Svend

  • 0 in reply to svendbt
    Prodigy 170 points
    Hi Svend,

    Thanks for the advice. I'm getting some prototype beacons made with the cc2640 chip anyway, I was just concerned that if the chip in the sensortag was the only current draw and the sensors were not drawing current then the battery life stats provided by TI looked very optimistic!

    Thanks
    Adrian
  • 0 in reply to svendbt
    Guru 16361 points

    I noticed one interesting thing in the board.c for CC2650 SensorTag: the default pin configuration applies power to the 9-axis MPU. If you don't want that to be powered you need to explicitly set it low in your firmware, or edit the board.c and change the default.

  • 0 in reply to Robert Cowsill
    Prodigy 170 points
    Hi Robert,

    I'm very new to embedded development, I've had a look in board.c but can't see anything that looks like what you are referring to. Could you tell me what I need to change so that it isn't powered?

    Thanks
    Adrian
  • 0 in reply to Adrian Cox56
    Prodigy 170 points
    One of the LEDs stays on all the time which I assume, without testing, is quite a drain on the power. How can I disable this?
  • 0 in reply to Adrian Cox56
    Guru 16361 points

    Sorry, I should have been clearer on which board.c file I meant. There's one included in the example/template projects, but it #includes a second board.c file from the TI/RTOS installation folder.

    In my case that file is under CCS6.1\tirtos_simplelink_2_13_01_09\packages\ti\boards\SensorTag\CC26XXST_0120. In the array BoardGpioInitTable is a line beginning with Board_MPU_POWER and commented /* MPU initially on */. Changing the PIN_GPIO_HIGH on that line to PIN_GPIO_LOW will mean the MPU is switched off by default.

    Regarding the LEDs, as far as I can remember they're off by default in BoardGpioInitTable. It may be that you have some code using PIN_open and PIN_setOutputValue to switch on a LED at runtime. At least some of the samples do this in main.

  • 0 in reply to Robert Cowsill
    Prodigy 170 points

    I think one of my problems is I'm using the simpleBLEPeripheral sample from the resource centre but that's setup to use the main cc2650 dev kit and not the sensortag.

    The board.c file is different, the BoardGpioInitTable has different pins (it has 4 leds listed)

    I think I'll take the sensor tag project as my base and start from there, it may be easier!

  • 0 in reply to Adrian Cox56
    TI__Guru** 105180 points
    Hello,

    You can also refer to this TI Design: www.ti.com/.../TIDA-00374 for an optimized beacon HW & SW application.

    I will also direct you to the Measuring Bluetooth Smart Power Consumption App Note, which is available on the TI BLE Wiki. This will help you find a Adv rate that matches the expected batt life of your power source. Finding a balanced rate is key since broadcasting (i.e., "beaconing") is one of the most power-intensive operations in BLE.

    Best wishes
  • 0 in reply to JXS
    Prodigy 170 points

    Hi JXS

    Thanks, that's really helpful.

    Also, I have now managed to get the sensortag app paired down for just beaconing and the LED light remains off, this will be enough for now but I will be looking at the reference design you linked to.

    Adrian