On Fri, Dec 12, 2008 at 6:39 AM, w w <biscuitk...@gmail.com> wrote: > I'm new to GNU Radio and would like encode and decode manchester...I looked > through the documentation for manchester or L encoding but did not see any > thing. I was wondering if someone could point me in the right direction?
There isn't a ready-made GNU Radio block for either encoding or decoding Manchester-coded signals; you'll need to write your own. This is done using C++ and is exemplified by the gr-howto-write-a-block subdirectory in the tree. Since you are new to GNU Radio, I highly recommend that you first familiarize yourself with existing flowgraph concepts by studying the examples provided, and achieve an understanding of overall GNU Radio operation with existing blocks. Then, study the C++ code for existing blocks to see examples of how various DSP techniques are implemented within. While Manchester coding itself is a fairly simple algorithm, the GNU Radio runtime environment will add a degree of complexity to your implementation. A common pitfall for beginning GNU Radio users is to dive right into custom blocks, or worse, into GUI programming with custom blocks, and struggle to learn five different things at once instead of one at a time. Save yourself some grief :) Things to keep in mind: * If you're operating at passband using FSK, there *will* be a time-varying frequency offset between your transmitter and receiver. This will show up as a wandering DC level after FM demodulation and you'll need to track this out before slicing to bits. * Even at baseband, there will be timing differences between what your transmitter and receiver consider one bit period. Since Manchester-coded signals are self-clocking, in an analog world this would not be an issue. In an SDR implementation, you'll need to oversample and implement a digital PLL to keep the transitions centered within the bit period. Have fun... -Johnathan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
