I have to develop a system for RFID operating in the 433 MHz frequency band (ISO 18000-7) transmission with the GNU radio python framework. I succeded transmitting a simple message with bfsk modulation using the gr.cpfsk_bc block with the proper parameter (carrier frequency, frequency deviation, bitrate). I'm trying now to implement the data link layer according to which data is sent in packet format, a packet is comprised of a preamble, data bytes and a final logic low period. Data bytes are sent in Manchester code format. The problem is: the length of the preamble pulses and the lenght of the data bit period are different, but I can only specify one bitrate in the gr.cpfsk_bc block (well not exactly the bitrate, the modulation index and the number of output samples per input bit, which depend on the bitrate). Have I to vary the bitrate according to which part of the packet I am transmitting? Or have I to choose one bitrate and to vary the sequence of symbol to reproduce the proper period length? Are there any helper function int the framework to do the job? What the simple_framer block exactly does, are there other blocks dealing with framing.
Andrea _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
