Prototype of a WiFi equipped sensor node
I recently built a prototype for a wireless sensor equipped with WiFi (instead of our regular sub-ghz radio). WiSense will soon be offering WiFi based sensors (in addition to sub-ghz radio based sensors).
We decided to use the CC3100 WiFi network processor. I interfaced the CC3100 to our MSP430 board and ported the simpleLink host driver (from TI) to MSP430. This allows us to leverage our existing code base which supports a large variety of sensors. The same code base now supports both WiFi (CC3100) and the CC1101 sub-ghz radio.
I ran the simple UDP client application (on the MSP430) to send data to my laptop (connected to the same AP).
The CC3100 supports 802.11b, 802.11g and 802.11n. It has on chip support for TCP and UDP.
The CC3100 has been designed to support different low power application scenarios. Let us say we need to sense some parameter once in a while (say every 30 minutes) and report the sensor value to the cloud. Such a node can be powered by a couple of AA batteries for a year or longer. This can be achieved by putting the CC3100 into hibernation in which it consumes just 4 micro-amps. When sensor data needs to be sent, the CC3100 can be woken up. Once awake, the CC3100 will rejoin the AP and send application data. The CC3100 can be put back into hibernation mode right away. Obviously this all depends on reliable connectivity to an AP.
The CC3100 can be interfaced to a host microcontroller over SPI or UART. We chose the SPI interface. The single UART port on the MSP430G2955 is free to be interfaced with any compatible sensor.
The one downside to the CC3100 is it’s cost. Avnet is quoting the lowest price ($10.1 each for 100 numbers).
Here is a functional block diagram of the system.
Here is a pic of the CC3100 interfaced to our MSP430G2955 board. Both are powered by a pair of AAA batteries.
Stay tuned for more posts on this chip.