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Chibi Release v0.81 | Print |
Written by Akiba   
Tuesday, 01 June 2010

Hi all.

Just a quick word to let you know that the Chibi stack has been updated to v0.81. This is just a minor update to add support for the TI CC1190 RF front end and coincides with the release of the AT86RF212-CC1190 board . If you've been interested in what it'd be like to match the AT86RF212 with the TI CC1190, you can check it out at the store. The schematics, layout, and BOM can be found inside the datasheet as usual. And in case you're wondering...the range is pretty sick :)

I made one other modification to the Chibi stack which was to move the command table into the main file as well. It used to be in a separate file so when you added commands to the shell, you had to add the functional code in one file, the prototype in the header, and then the command in a separate file. It was a big hassle so now adding a command can be all done within one file. Part of the reason I changed this is that I'm preparing a tutorial on Chibi and when I heard myself trying to explain it, it made me want to cry. Anyways, that mod was mostly just to simplify things. 

Guess that's about it for now. Back to bringing up the other boards and writing tutorials...Hi-ho, Hi-ho...

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Keep it up
written by André, June 02, 2010
Keep up with the good work!

I thank you for it.
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How well does the CC1190 receive amp work with the AT86RF212?
written by Conn Clark, June 02, 2010
Akiba,

I was just wondering how well the CC1190 receive amp worked with the AT86RF212? Have you done any actual range testing? I know that receive amps can be a real pain to get right.
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written by Akiba, June 02, 2010
I connected a coax from the output of a AT86RF212 board to the input of the CC1190-RF212 boards and transmitted at the lowest power and with a 40 dB attenuator. I did see an 11 dB boost in the RSSI with the LNA enabled. Unfortunately, that's about as sophisticated a test as I can perform at the moment since I don't have enough equipment to do a better RF analysis. Once I can get enough money, I'm hoping to get a spectrum analyzer, signal generator, and variable attenuator which would make characterizing much easier. That will probably take some time though. At the moment, the best I can do is ensure a good impedance match using the network analyzer.

I haven't had a chance to do an open field range test since open areas in Tokyo are very hard to come by. Tokyo Hackerspace has a project coming up where we're going to be instrumenting a farm out in the countryside. The site survey is going to happen in July and I'll be taking out a bunch of boards to test at that time as well. I did do a rough range test which is just having the board on my balcony and then walking down the street. The board easily outperformed any boards I currently have by a huge factor.
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written by Conn Clark, June 03, 2010
Akiba,

Receiver amps can't really be measured by gain. Receive amps are dominated by noise factor. You can get an idea of realistic improvement over your other board with a short range test. You will need 2 of your 900 MHz, 802.15.4 Radio Peripheral boards and one high powered board.

Configure one unit to be a transmitter and have it set to transmit at very low power. Move your high power board with the receive amp to a point to where it starts to drop packets. Next place the other low power unit at the same point using the same antenna. Finally increase the power of the transmitter until the low power receiving board starts to receive the packets and is dropping just about as many as the high power unit did. Finally you measure the difference between the two power settings of the transmitter and that is the effective improvement.

Since you said you didn't have a spectrum analyzer you could use a third 900 MHz unit at a fixed range close to the transmitter and measure the change in rssi levels with that for a good approximation.

good luck

Conn
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written by Akiba, June 03, 2010
Hi Conn.
Thanks for the detailed instructions. I'm a little hesitant to do the test in open air though because my area is very bad for RF. I'm surrounded by tall buildings and I see a lot of variance outside in RSSI so it seems there's quite a bit of multi-path.

I'm going to start looking for a variable attenuator though and try out the test using conducted lines. That way, I won't have to worry about reflections and get reliable results.
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