TIDUE59A May   2018  – September 2020

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5. 1System Description
    1. 1.1 Key System Specifications
  6. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 CC3220
      2. 2.3.2 CC2640R2F
      3. 2.3.3 DRV8837
    4. 2.4 System Design Theory
      1. 2.4.1 CC3220S to CC2640R2F Interface
      2. 2.4.2 CC3220S to DRV8837 Interface
      3. 2.4.3 Software Architecture
      4. 2.4.4 Network Connection Management
      5. 2.4.5 Provisioning
        1. 2.4.5.1 AP Provisioning and SmartConfig™
        2. 2.4.5.2 Wi-Fi Provisioning Over BLE
      6. 2.4.6 Sending and Receiving Messages Through Cloud
        1. 2.4.6.1 Message Queue Telemetry Transport Protocol
        2. 2.4.6.2 MQTT Client Implementation
      7. 2.4.7 Over-the-Air Updates
        1. 2.4.7.1 HyperText Transfer Protocol
      8. 2.4.8 Security Enablers
        1. 2.4.8.1 Secure Boot
        2. 2.4.8.2 Secure Sockets
          1. 2.4.8.2.1 Hardware Accelerators
          2. 2.4.8.2.2 Simple Network Time Protocol
        3. 2.4.8.3 File System Security
          1. 2.4.8.3.1 Failsafe Files and Bundle Protection
      9. 2.4.9 Low-Power Consumption
  7. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
        1. 3.1.1.1 CC3220S LaunchPad™ Development Kit
        2. 3.1.1.2 CC2640R2F LaunchPad™ Development Kit
        3. 3.1.1.3 Sensor BoosterPack™ Connections (BMI160)
        4. 3.1.1.4 DRV8837EVM Modifications and Connections
        5. 3.1.1.5 Assembling EVMs
      2. 3.1.2 Software
        1. 3.1.2.1 Getting Started With Software
          1. 3.1.2.1.1 Build simple_np Application and Flash CC2640R2F
          2. 3.1.2.1.2 Use Premade UniFlash ImageCreator Project
          3. 3.1.2.1.3 Importing Project Source Files Into CCS
        2. 3.1.2.2 User Files
        3. 3.1.2.3 Run Wi-Fi® Doorlock Demo
          1. 3.1.2.3.1 Connect CC3220 to Network
          2. 3.1.2.3.2 Networking Functions
            1. 3.1.2.3.2.1 Get Current Date and Time (SNTP)
            2. 3.1.2.3.2.2 Send and Receive Messages (MQTT)
            3. 3.1.2.3.2.3 Perform Software Update Using Dropbox (OTA Update)
    2. 3.2 Testing and Results
      1. 3.2.1 Pass or Fail Tests
      2. 3.2.2 Power Measurements
      3. 3.2.3 Test Setup
        1. 3.2.3.1 CC3220S
        2. 3.2.3.2 CC2640R2F
        3. 3.2.3.3 DRV8837
      4. 3.2.4 Test Results
      5. 3.2.5 Battery Life Estimate
  8. 4Design Files
  9. 5Software Files
  10. 6Related Documentation
    1. 6.1 Trademarks
  11. 7Terminology
  12. 8About the Author
  13. 9Revision History

3.2.5 Battery Life Estimate

The experimental results from Section 3.2.4 can be used to estimate the battery life of a system that is based on this design. Based on the results in Section 3.2.4 and using the assumption that the electronic smart lock is locked or unlocked 24 times per day, users can estimate the power consumed by each subsystem.

The main parameters of the Wi-Fi subsystem that affect the estimated battery life are as follows:

  • CC3220 supply voltage: 3.3 V
  • Idle connected current: 377 µA
  • Average current during a lock or unlock event: 12.12 mA
  • Duration of a lock event: 2 seconds
  • Average current when reading lock status: 11.82 mA
  • Duration of a lock status event: 1.6 seconds

Equation 1 gives the average Wi-Fi idle power.

Equation 1. GUID-96B9DC0D-7D7B-453A-AD26-82925E662DAB-low.gif

Equation 2 gives the average Wi-Fi power per day, due to locking and unlocking.

Equation 2. GUID-80AA59E3-E48B-4BEA-9EAF-44FAB1779D9B-low.gif

Equation 3 gives the average Wi-Fi power per day, due to the checking lock status.

Equation 3. GUID-180A71BD-09F6-483E-BAE4-9FC8D560B1DF-low.gif

Equation 4 gives the approximate average Wi-Fi power.

Equation 4. GUID-425BB5C2-8B1C-4A0A-A03A-EB0C5BB43C3D-low.gif

The main parameters of the BLE subsystem that affect the estimated battery life are as follows:

  • CC2640R2F supply voltage: 3.3 V
  • Average current of the CC2640R2F after provisioning: 40.23 µA

Equation 5 gives the approximate average BLE power.

Equation 5. GUID-0A946930-D55E-4DD5-9634-8A0FD79CCE78-low.gif

The main parameters of the motor driver subsystem that affect the estimated battery life are as follows:

  • DRV8837 motor supply voltage: 5 V
  • Average DRV8837 sleep current: 0.099 µA
  • Average current while locking deadbolt: 77.62 mA
  • Average current while unlocking deadbolt: 73.15 mA
  • Average time spent driving the motor: 2 seconds

Equation 6 gives the average motor driver idle power.

Equation 6. GUID-B8CF5C26-0DA6-4F6E-8831-D147024F2111-low.gif

Equation 7 gives the average motor driver power during a lock event.

Equation 7. GUID-9F29A161-3741-4317-8AB3-8C1F6EB970A2-low.gif

Equation 8 gives the average motor driver power during an unlock event.

Equation 8. GUID-1B5CDA32-6D24-490D-A6CB-B1E86DCD6F80-low.gif

Equation 9 gives the approximate average motor driver power.

Equation 9. GUID-B2195168-B502-4AA9-A64C-EF1F333D574A-low.gif

Using the calculations for the power consumed by the Wi-Fi, BLE, and motor subsystems, users can estimate the total average system power (see Equation 10).

Equation 10. GUID-46FC5F21-284B-4669-AEF3-5B1F9B3FB08E-low.gif

The estimated total system power can be used to estimate the battery life of the system, using the theoretical energy capacity of the power source. For this estimate, assume an energy capacity of 18,000 mWh and calculate the months of battery life using Equation 11.

Equation 11. GUID-7D2F4D18-6989-4619-9EAF-D545EBD5ACDC-low.gif