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copied!<p>Here's an alternative protocol:</p> <pre><code>u8 Sync // A constant value which always marks the start of a packet u16 Length // Number of bytes in payload u8 Data[Length] // The payload u16 Crc // CRC </code></pre> <p>Use RS232/UART, as the PC (serial port) and the processor (UART) can already handle that with minimum fuss (just need a <a href="http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1798" rel="nofollow noreferrer">MAX232</a> chip or similar to do the level shifting).</p> <p>And using RS232/UART, you don't have to worry about master/slave if it's not relevant. Flow control is available if necessary.</p> <p>Suggested PC software: either write your own, or <a href="http://www.fuh-edv.de/docklight/" rel="nofollow noreferrer">Docklight</a> for simple monitoring and control (evaluation version is free).</p> <p>For greater error checking, simplest is parity checking, or if you need something more powerful, maybe <a href="http://en.wikipedia.org/wiki/Convolutional_code" rel="nofollow noreferrer">convolutional coding</a>.</p> <p>In any case, whatever you do: <strong>keep it simple!</strong></p> <p><strong>EDIT:</strong> Using RS232 with a PC is even easier than it used to be, as you can now get USB to RS232/TTL converters. One end goes into your PC's USB socket, and appears as a normal serial port; the other comes out to 5 V or 3.3 V signals that can be connected <em>directly</em> to your processor, with no level-shifting required.</p> <p>We've used <a href="http://www.ftdichip.com/Products/EvaluationKits/TTL-232R-3V3.htm" rel="nofollow noreferrer">TTL-232R-3V3</a> from FDTI Chip, which works perfectly for this kind of application.</p>

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