A new top-level component, gr-gpio, has recently been merged into the trunk.
gr-gpio is an extension to the normal USRP firmware, implemented as an alternative FPGA bitstream, using the exising USRP host code. With the gr-gpio component you can transmit and receive a digital stream to and from the USRP which is aligned with the existing analog stream. Digital data is sent to or received from the daughterboard GPIO pins and sacrifice one bit each from the I and the Q analog streams to transport the digital bits. Receiving Streaming Digital Samples ¶ Digital streams are sampled from GPIO 14 and GPIO 15 from the selected daughterboard and replace the LSB of the I and Q analog streams, respectively. In the host, on can then use usrp.source_s() to obtain the combined streams and seperate them with logical bit operations. The GPIO pins are sampled at the decimated RF rate; that is, the GPIO data replaces the LSBs at the output of the digital downconverter. As a result of pipeline delays in the analog processing stream, there will be a fixed but decimation rate dependent delta between the analog and digital streams. Transmitting Streaming Digital Samples ¶ In the host, one uses usrp.sink_s() and encodes the desired digital data into the LSBs of the I and Q sample data. These are then routed to GPIO 14 and GPIO 15 of the selected daughterboard. The data is output on the GPIO pins at the same rate as the sample data arriving over the USB. Due to pipeline delays in the analog processing stream, there will be a fixed but interpolation rate dependent delta between the analog and digital streams. Full documentation is available at: http://gnuradio.org/trac/wiki/CompGrGpio -- Johnathan Corgan Corgan Enterprises LLC http://corganenterprises.com/ _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
