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. 

Just thought I would give everyone a quick heads up that Atmel released their RZRAVEN Zigbee Dev Board firmware a few weeks ago. I just found out about it now when I was browsing around their website. The source code looks like it's completely open, but the license agreement limits the usage of the software to Atmel products only, basically the same as Microchip and TI. The firmware contains some interesting applications such as a packet sniffer application that allows you to inject frames and also jam the signals. You need to register to download the firmware. Here's the link.

It was a busy week last week. Japan's Golden Week holidays start this week which is a week-long vacation. That means that last week, everyone was scrambling to get things done so they wouldn't get delayed or have to come in during the holidays. My two-day work week turned into a full week of work, which sucks because I only get paid for two days. They said that I can get compensation days this week, but this whole week is a vacation. I've been tricked! 

Anyways, I did get a chance to sneak away and go to the Tokyo Sensor show so I thought I would post the pictures from it. I spared everyone the pictures of pressure, light, and other types of sensors since they aren't too exciting. In fact, there wasn't a whole lot exciting at the show from the companies. All the really cool stuff came from the university research projects. That just goes to show me the difference between corporate and non-corporate creativity. I'll take a cool university research project over a powerpoint product roadmap any day. That reminds me...I need to make the software roadmap for this project. Ha ha ha.

Here's the pictures...   

An interesting question was asked in the forums which, although reworded,  goes something like this:
"Why do the Zigbee SOC offerings have very little resources?"

This is actually an interesting question and to answer it requires a bit of a background on IC design.

Semiconductor hardware is all about cost, at least it is these days. The times are long gone when semiconductors was a glam industry. Consumer devices and PC products are all pushing down costs like crazy and the manufacturers are constantly pressuring the semiconductor suppliers to reduce their price. This is especially rampant in the standard products market, which includes the likes of ethernet, 802.11, and (if it takes off) 802.15.4 chips since they are all based on open standards.