Saturday, January 3, 2009

Implementing the MSP430 FET Protocol

by Travis Goodspeed <travis at radiantmachines.com>
continuing initial observations.

Following a comment posted to the prior article, I discovered that, as suggested, the PPP FCS-16 checksum is the one used for communicated with the FET. Searching MSP430.dll for the initial bytes of the checksumming table which is presented on Section C.2 of RFC1662, yields the following table,
CRC16 Function from MSP430.dll

The 16-bit entries from the table appear as little endian, so {0x1189, 0x2312} becomes {0x89, 0x11, 0x12, 0x23}. Running a quick test with the RFC's FCS-16 code yields a proper checksum, with which messages can be signed.

The result of this is an open source too, MSP430FET, for programming chips with the MSP430 FET tools. The present version can read and write memory, but it is limited to spy-bi-wire and is unable to erase memory. Expect those features, and a website, in a later revision.

svn co https://msp430fet.svn.sourceforge.net/svnroot/msp430fet/trunk msp430fet

1 comment:

Travis Goodspeed said...

'erase' and 'loadihex' commands have now been committed to SVN, and I've successfully written a complete firmware image to a chip.