SWRA578B October   2017  – April 2020 CC1312PSIP , CC1312R , CC1314R10 , CC1352P , CC1352P7 , CC1352R , CC2620 , CC2630 , CC2640 , CC2640R2F-Q1 , CC2642R , CC2642R-Q1 , CC2650MODA , CC2652P , CC2652R , CC2652R7 , CC2652RB , CC2652RSIP

 

  1.   Ultra-Low Power Sensing Applications With CC13x2/CC26x2
    1.     Trademarks
    2. 1 Overview
    3. 2 Measurement Conditions
      1. 2.1 Software
      2. 2.2 Hardware
    4. 3 Measurements
      1. 3.1 BOOSTXL-ULPSENSE
        1. 3.1.1 Analog Light Sensor
        2. 3.1.2 Capacitive Touch
        3. 3.1.3 LC Flow Meter
        4. 3.1.4 Potentiometer
        5. 3.1.5 Reed Switch
        6. 3.1.6 SPI Accelerometer
      2. 3.2 LPSTK-CC1352R
        1. 3.2.1 I2C Light Sensor
        2. 3.2.2 I2C Temperature and Humidity Sensor
        3. 3.2.3 SPI Accelerometer
        4. 3.2.4 Hall Effect Sensor
      3. 3.3 Comparison with System CPU
        1. 3.3.1 4 MHz SPI Transfer
        2. 3.3.2 1 MHz SPI Transfer
        3. 3.3.3 Wake-up and Sleep
    5. 4 Summary
    6. 5 References
  2.   A Creating the comparison examples
    1.     A.1 SPI Transfer – Sensor Controller
    2.     A.2 SPI Transfer – System CPU
    3.     A.3 Wake Up and Sleep – Sensor Controller
    4.     A.4 Wake up and Sleep – System CPU
  3.   Revision History

4 Summary

By using the Sensor Controller, ultra-low power consumption can be achieved when using different sensors. This table summarizes the current measurements for the BOOSTXL-ULPSENSE examples in Sensor Controller Studio.

Average Current Consumption Unit
Analog light sensor (10 Hz) 9.2 µA
Capacitive Touch (32 Hz) 8.1 µA
LC Flow Meter (100 Hz) without flow 5.9 µA
LC Flow Meter (16 Hz) without flow 1.7 µA
Potentiometer (25 Hz) 1.7 µA
Reed Switch without magnet present (64 Hz) 1.3 µA
SPI Accelerometer (100 Hz) 5.4 µA

The sensors found on the LPSTK-CC1352R also showed low power capabilities. Note that these numbers include the minimal standby current for the unused sensors, since the sensors on the LPSTK-CC1352R board cannot be powered off.

Average Current Consumption Unit
I2C Light Sensor 2.98 µA
I2C Temperature and Humidity Sensor 3.48 µA
SPI Accelerometer 6.24 µA
Hall Effect Sensor 2.30 µA

When comparing the Sensor Controller to the System CPU, the Sensor Controller has significantly lower current consumption.

Average Current Consumption Unit
1 wake-up per Second 10 wake-ups per Second 100 wake-ups per Second
4 MHz SPI - Sensor Controller active mode 1.1 2.8 19.3 µA
4 MHz SPI - System CPU 3.2 21.0 222.8 µA
1 MHz SPI - Sensor Controller low-power mode 1.1 1.2 3.2 µA
1 MHz SPI - System CPU 3.5 23.7 218.6 µA
Wake-up and sleep - Sensor Controller low-power mode 1.0 1.1 1.3 µA
Wake-up and sleep -Sensor Controller active mode 1.1 2.5 12.8 µA
Wake-up and sleep - System CPU 2.2 8.5 112.6 µA

The different examples shown in this application report use many different techniques to reduce the power consumption. Some ways that low power consumption can be achieved are shown here:

  • Low-power mode instead of active mode where possible.
  • Timer 2 in low-power mode instead of TDC, where possible.
  • SPI instead of I2C, where possible.
  • Timer 2 at 32 kHz to power up the sensor and then wake up the Sensor Controller (when the sensor is ready).
  • Timer 2 at 2 MHz/32 kHz as pulse width modulator (PWM) for status LEDs.
  • Preprocess the sensor data to detect relevant activity, and wake up the System CPU application only when needed.
  • General-purpose input/output (GPIO) event handler for interrupt from digital sensor, with timeout for sensors that generate interrupt periodically.
  • Minimized communication over I2C/SPI, reading multiple external device registers in one operation.
  • Disable peripherals as soon as possible after measurement (before the data processing).
  • Reduced sensor polling frequency when the sensor data indicate no activity.
  • Reference DAC and COMPA in low-power mode can be used as low-precision ADC.