Lets start at the top. The first line gives feedback on the FIFO’s status. The first entry displays how many 1 ms nodes are left in the FIFO, 999 representing the FIFO is empty. If the receiver starts to bog down this will decrease. The next value presents how many milliseconds in total have been processed. The third value is the AGC scale factor, basically a divisor that holds the number of overflows in each ms to a constant number. The final value is the number of overflow in the last ms.
The next block shows the tracking channel status. From left to right, the channel number, SV assigned to the channel, the integration length (in ms), the value of the acceleration accumulator in the PLL/FLL, the Doppler value in Hz, the CN0 estimate in dB-Hz, the bit edge, tracking locks, I2+Q, and finally the number of seconds this SV has been tracked. The tracking lock display has the following codes:
pBFN12345
f/p: FLL or PLL tracking
B: bit lock
F: frame lock
N: this channel is being used for navigation
12345: the last decoded subframe
The next block displays some info about the navigation, again from left to right, the channel number, SV assigned to the channel, time used in SV position calculation, SV ECEF X velocity, ECEF Y velocity, ECEF Z velocit, pseudorange (seconds), and finally pseudorange residual (meters).
The latest acquisition result is display in the next line, the labels in the screenshot should be self explanitory. Acq type is STRONG (1 ms) or MEDIUM (10 ms).
The navigation display should be easily understood. One thing is missing from the screenshot, after the last line, when an SV’s ephemeris is succesfully decoded the SV number will appear in comma delimited list. This will not happen for those running the receiver on the 10 second snapshot of data I posted, but those who succesfully run the receiver on top of the USRP in real-time should see it. As always, I appreciate all of the questions and feedback.
