I would like to ask a few questions regarding USRP, UHD and GNU Radio.
I have 2 USRP devices and one module I bought that’s able transmitt and
receive on 433.92 MHz. I installed UHD on 2 computers (both with Win XP
OS), connected to each one a USRP1 that has a WBX daughterboard and a
Log Periodic type antenna by Kent Electronics that’s on Ettus order
page. Both USRP’s are recognized.
I would like to send some data packets that will have FSK and GFSK
modulation. With one USRP I will receive data coming from the module and
data coming from the second USRP. Each packet will have some data in it
to be identified, so that I could log it. As I am a newbie I would like
to ask if there are any test examples for GRC or simply Python to modify
it to meet my requirements. Honestly I don’t know where to start. There
are blocks for AM, FM, DPSK, GMSK, QAM and others, each one heaving a
MOD and DEMOD block but no blocks for FSK.
My packets will have the following layout a Preamble, a Header for
identification, a number of bytes of data, and CRC data at the end. At
transmitter I send data packets (many 1/0 values that are put on a
carrier signal - in FSK signal we have a frequency for the 1 and a
different frequency for 0). If there were a block to demodulate FSK
modulated sugnals it would pass me some 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1
… from which I would have to recognize my header, if I recognize it,
then the next byte of data should be the representation of the length of
data, to know how many bytes I will have to receive until I reach to the
end where I will have to know the length of my CRC data. After I receive
the CRC the packet is finished, I can process data that I will put
previously into a buffer and start to interprete bytes of data (who sent
the packet, etc.). If CRC is not the same as received then it means it
has errors and data is not usable. Is it correct how
I’m thinking the problem or I should tink in a different way.
My first steps will be to try some source code in Python but after
that I plan to make my own interface to control these devices (the
second USRP and the module). I don’t really know how to get the I/Q data
from USRP, how to set different parameters likecenter frequencyand
others. There’s any partial or full documentation related to this. If I
could use the Visual Studio I would be able to make some GUI. If there’s
no souce code written for FSK maybe based on other codes written for
other modulation types, I will make one, but ther’s little chance for
that to work, anyway I will have to know how to get I/Q data from USRP,
how to write .rbf file toFPGA, and others.
Thank you very much.