According to Vetti; how that power is distributed across the device depends on how it is used: "It is determined by the duty cycle of the RF, if you are transmitting all the time this is a bad idea if you want to save power. If you only transmit twice a day, the RF will be the smallest part."
The CC430 platform is, therefore, targeting applications that exhibit this kind of use pattern; they remain in sleep mode for the majority of the time, wake up infrequently and transmit a burst of data, and then return to sleep mode. With these applications comes the need for some obvious characteristics, such as a very short wake-up time, however more commonly required in today's applications " particularly for wireless devices " is the need for secure transmission, which implies some form of encryption.
The CC430 platform, therefore, also includes a hardwired AES encryption block (see figure 1). The core itself also features a hardware multiplier and DMA channels, and represents the lowest power MCU TI could implement in this platform.
As a result, Vetti believes it is particularly well suited to energy harvesting applications.
The next big challenge for Vetti and his team is delivering higher performance and to that end he is currently involved in the development of a new RF core, which will target higher performance and offer greater range: "There should be a high performance RF core that is suitable for integration available in the near future."
Moving forward in the sub-1GHz range, Vetti sees a continued need for separate transceivers, but in most other cases demand will be for SoCs, where more complex protocols and a greater need for security will likely dictate it.
Shine on
Creating applications that use only harvested power is perhaps a daunting prospect and one that may require more than just an application note. Because of that, TI has recently introduced a development kit that demonstrates how solar energy can convert ambient light in to power, to run a wireless node.
The eZ430-RF2500 isn't based on the new CC430 platform, but uses the same MSP430 MCU, with a separate transceiver from the same family; in this case the CC2500, which operates at 2.4GHz. The kit also features a thin-film battery, called EnerChip, from Cymbet Corp., a rechargeable battery in the form of a surface mount integrated circuit incorporating battery management logic.
TI claims it is taking the mystery out of RF design, with RF reference designs, SmartRF Studio software, an RF packet sniffer, and design notes.
Third Party software development providers are also contributing, in the form of IAR, while TI's own Code Composer Essentials IDE is also now available with MSP430 specific collateral.
With any number of applications for wireless networks that could exist without maintenance " even to the point of requiring a separate power supply " is likely to spawn a new phase in data gathering and its distribution. It is also likely to raise interesting issues, such as how much value to put on that data, and how to pay for it if the data is gathered from resources owned by others.
