1. Exercise: Reading the RSSI Value

One of the most frequently used measures in wireless communications is the “Received Signal Strength Indicator” or short RSSI. The RSSI is a measure related to the power of the signal. In contrast to the “Signal to Noise Ratio (SNR)”, which is also a measure of the power, the RSSI is not standardized. But, in most implementations the RSSI is proportional to the SNR. The SNR is the power of the transmitted signal divided by the power of the noise measured in decibel (dB).

The aim of this exercise is to create a program that measures the RSSI using the CC1200.

This task requires

• a ready BeagleBone Black equipped with the CC1200
• another BeagleBone Block equipped with the CC1200
• 4C.

• connect the first BeagleBone Black to your computer and install, execute 4C.
• open RX Synchronous Serial Mode in test window.
• export all registers to a file.
• connect the second BeagleBone Black to your computer and login as superuser.
• copy the SPI_test directory and modify it according page Programming CC1200
• copy the export file from 4C to the BeagleBone Black
• import the export file into your program and initialize the registers according the values of the export file.
• verify that the registers have been written correctly.
• Read chapter 6.9 about the RSSI of the CC1200 Users Guide and implement it.
• if the program is correctly compiled and linked start it. The RSSI must have values between -128db and 127db.
• If this is the case bring 4C in “TX RX Synchronous Serial Mode“ and start the transmitter. At the receiver, the BeagleBone Black, the RSSI should increase. If switching off the transmitter, the RSSI should drop down.

• a precision of 1dB of the RSSI is sufficient
• keep care, that representation of the RSSI is not an integer value, but a byte in two's complement presentation.