To start off the series on new 802.15.4 chip reviews, I've chosen the Atmel AT86RF230/231. The AT86RF230 and 231 are essentially the same chip, however the 231 has some extra features over that were noticeably lacking in the 230. One of the most important additions was a hardware security co-processor. They also added other nice features like antenna diversity, multiple data rates up to 2 Mbps (non-standard), random number generator, and they brought out the RX/TX switch. Since I've never done a review on the 230, let's start with some of the features of that chip. The 231 contains all of the same features as well as the above mentioned extras.

The 230/231 has all of the basic features of other chips out on the market. These include things like an SPI interface, 128-byte Rx and Tx fifos, and RSSI output. One of the nice features that they included was an energy detector which is useful for energy scans. Energy scans are used in 802.15.4 and Zigbee as part of starting a new network. You would scan the channels and choose the one with the lowest energy (least traffic) and fewest networks. Normally, you'd have to convert the RSSI into an energy detection value in software, however this is done automatically in the 230/231.

Another very convenient feature they included is Link Quality Indication (LQI). This is a statistical value of the quality of the link and can be correlated to a packet error rate. The reason why this feature is valuable is that packet error rate is used in Zigbee to calculate the path cost for each router hop. A route will be chosen based on the lowest path cost, and to calculate the cost of a link, you would need to use some type of statistical algorithm in software. Since the hardware maintains a running history of the link quality of all frames, the statistical value should (hopefully) be pretty accurate. 

Lately, I've been working on the stack every day and I need a bit of a change of pace. Only reading hex data and debugging logic errors every day is not good for the soul. Also, the blog has been a bit neglected recently except for my devjournals so I thought I'd start working on a series of chip reviews about the recently released ones. I've been asked by a couple of people to provide reviews for chips over the past few months, but I never got around to it. Since it doesn't require any coding and only requires me to give my own stubborn opinion, I thought it'd be a nice breather for me. It will also give me a chance to learn more about the new chips that have recently made their way on to the market. The chips that I'm targeting for review are the Atmel AT86RF231, GreenPeak GP500C (no datasheet available yet it seems), and the recently announced Freescale MC13224 SoC (PiP?).

I should also mention that these reviews are based on the chip datasheets only and not on actual usage. I'm hoping to change that soon, though :)