Functional example – TI SensorTag CC2650

The Texas Instruments CC2650 SensorTag is a good example of an IoT sensor module for development, prototyping, and design. SensorTag has the following features and sensors in the package:

• Sensor input
  • Ambient light sensor (TI Light Sensor OPT3001)
  • Infrared temperature sensor (TI Thermopile infrared TMP007)
  • Ambient temperature sensor (TI light sensor OPT3001)
  • Accelerometer (Invensense MPU-9250)
  • Gyroscope (Invensense MPU-9250)
  • Magnetometer (Bosch SensorTec BMP280)
  • Altimeter/Pressure sensor (Bosch SensorTec BMP280)
  • Humidity sensor (TI HDC1000)
  • MEMS microphone (Knowles SPH0641LU4H)
  • Magnetic sensor (Bosch SensorTec BMP280)
  • 2 Push-button GPIOs
  • Reed relay (Meder MK24)
• Output devices
  • Buzzer/speaker
  • 2 LEDs
• Communications
  • Bluetooth Low Energy (Bluetooth Smart)
  • Zigbee
  • 6LoWPAN

This package is powered by a single CR2032 coin cell battery. Finally, the device can be placed into beacon mode (iBeacon), and used as a message broadcaster. Following is the block diagram of the CC2650 SensorTag module:  

TI CC2650 SensorTag. Courtesy of Texas Instruments, TI Multi-Standard CC2650 SensorTag Design Guide. Texas Instruments Incorporated, 2015. 

The next image is of the block diagram of the MCU. The MCU provides the IO and processing ability using an ARM Cortex M4, and connects over various bus interfaces to sensor components on the module:

TI CC2650 MCU Block Diagram. Courtesy of Texas Instruments, TI Multi-Standard CC2650 SensorTag Design Guide. Texas Instruments Incorporated, 2015. 

This device is packed with a number of sensors, communication systems, and interfaces, but the amount of processing power is limited. The device uses a processing module from TI (MCU CC265), which includes a small ARM Cortex M3 CPU with only 128 KB of flash memory and 20 KB of SRAM. This was chosen for its extremely low power consumption. While power-efficient, this limits the amount of processing and resources on this system. Typically, components like these will need to be accompanied by a gateway, router, cell phone, or some other smart device. Sensor devices such as these that are built for low power and low cost would not have the resources for more demanding applications such as MQTT protocol stacks, data aggregation, cellular communication, or analytics. For that matter, most endpoint sensing devices one will see in the field are simpler than this component, to further reduce cost and power.