Palm interface for the '7747

[Ludis Langens]

Reid Bishop wrote:
> 
> My Palm currently only interfaces to a '7747 ECM (160 Baud only).  This
> required a hardware interface, as the Palm couldn't possibly do the 160 baud
> C3 protocol.

Yes it can!

Set the UART to a baud rate a bit faster than 1600, up to perhaps 3000
baud.  2000 baud might be a good starting point.  At this baud rate, you
will receive one byte per every 160 baud ALDL bit.

Short ALDL pulses ("0" bits) will be received as bytes of 0xff, 0xfe, or
maybe 0xfc.  Long pulses ("1" bits) will by received as 0x00, 0x80,
0xc0, or maybe 0xe0, depending on the baud rate the UART is set to.  All
that remains to do is software process the bytes from the UART -
converting them to the ALDL data packet.

A great thing about this method is that the interface hardware that
works for 160 baud ALDL will also work for 8192 baud.  All that needs to
be done is set the UART to 8192 baud and use a different software driver.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/


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