|Introducing the Freakduino 900 MHz Long Range Wireless Board v2.1a||| Print ||
|Written by Akiba|
|Wednesday, 25 September 2013|
I'm proud to introduce the latest addition to the Freakduino family. This is the Freakduino 900 MHz Long Range wireless board. On the outside, it looks fairly similar to the other Freakduino boards, but under the hood, it's tuned to communicate over long distances. This board uses the same radio as the standard Freakduino 900 MHz board but adds a TI CC1190 RF front end. This boosts the transmit power from 10 mW (+10 dBm) to 500 mW (+27 dBm). There's also a low noise amplifier on the receiver which gives the received signal an +11 dB boost (>10X). Altogether, this chip adds +38 dB to the link budget which is massive gain in the wireless world.
I originally designed this circuit a few years back when I was looking for something to do long distance wireless sensor links, on the order of kilometers or tens of kilometers. 2.4 GHz gets a bit hard to drive that far since higher frequencies have more attenuation in free space as well as a difficult time going through objects. Lower frequencies have much less attenuation and are able to travel through obstacles more easily so they're ideal for situations where range is valued over speed. In sensor networks, data rate usually has a low priority compared to battery life and communications range.
Along with having amplifiers on the transmitter and receiver, the Freakduino 900 MHz long range wireless board sports a sophisticated radio with many advanced features. The radio supports the standard 780, 868, and 902 to 928 MHz license free bands making it compatible with most countries in the world. It also supports the standard O-QPSK modulation and BPSK modulation as well as special high data rate modes up to 1 Mbps. O-QPSK modulation offers faster data rates such as 250 kbps to 1 Mbps, while BPSK modulation has lower data rates such as 20 to 40 kbps but improves the communications range. The radio also has hardware and driver support for AES-128 encryption and true random number generation.
Another feature of this board is its power mangement. The hardware is optimized for low power operation and in sleep modes, only consumes 300 uA at 3V (2-AA batteries). This would theoretically allow 2-AA batteries to power this device for months with proper power management and low duty cycles. The battery boost circuitry differs from the standard Freakduino series in that it has two separate boost circuits. During transmission, the front end amplifier puts a lot of power into the signal so the boost converters were doubled up to support both the wireless circuitry and still have spare current for other devices attached to the board.
The rest of the feature set is standard for all Freakduinos and consists of Arduino compatibility as well as optional ruggedized enclosure and bottom mounted battery pack. There's a much better description of it all in the documentation so I won't go over it all here. The main buying point for this board is the combination of the 900 MHz Atmel radio and the TI CC1190 amplified RF front end. That makes it possible to have both a low power wireless system and to be able to communicate over long distances. Putting these together with high gain directional antennas and good land topology would allow people to build wireless links over tens of kilometers and is perfect for applications such as environmental monitoring or building automation across multiple floors or large buildings.
I'm looking forward to the possibilities and applications that people come up with for this board :)For this first week, the boards will be selling at a 10% discount. Get 'em while they're hot!
written by Double side fusible woven interlining, November 14, 2013