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Launchpad rfm12b rf spectrum analyzer

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this is my entry to the Nov-2010 project contest, in this thread http://www.43oh.com/forum/viewtopic.php?p=1148#p1148




brief description

this is a simple rf spectrum analyzer project based on TI Launchpad. i have been working on other rf transceiver projects and in need of a simple rf spectrum analyzer to help me visualize what's happening.


a RFM12B module is used to capture signal strengths of different frequencies. the RFM12B utilizes a SPI interface to communicate to a MCU. a software SPI is implemented in this project for simplicity.


the Launchpad firmware basically received commands from the PC side perl script to start sampling for signal strengths, the frequency and signal strength are then sent to a host application (written in perl) for visualization. there is a threshold in the firmware that prohibits data sending if the signal strength is below it. this is needed as the LaunchPad can only do 9600bps communicating w/ the PC and if we include all the zeros and noises for sending, the uart is not able to catch-up.


on the PC side, the perl script will send a "start" command during start-up. it then reads data from the Launchpad, continuously updating the display grid to show "near" real-time results. there are some other settings on the perl script that affects the visualization and is described separately.


although the RFM12B module i used is tuned for 915Mhz, i am able to get signal strengths (may not be optimized) from the 433Mhz and 868Mhz bands.


thank you in advance for any comments, suggestions, etc.


http://www.simpleavr.com/msp430-project ... m-analyzer

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it's RSSI, initially i used a DRSSI function from the RFM12B module. i access this function via SPI. but it was too slow and got almost no resolution. i researched a bit and understand this thing also has ARSSI (mentioned but not documented on datasheets).


i am now using the ARSSI (need to draw this pin out from a resistor pad on the PCB) and thanks for the speedy MSP430 ADC, able to capture ARSSI reliably and quick. it's a lot of trials and errors to get it working as there are not much information on how to use it.

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