Home-brewing an ignition advance control

[Bill the arcstarter]

Greeting diy_efi list, 
 I wrote:
> recently.  Looks like a winner.  Another fun chip is the Linear Tech 
> LTC1294.  This is a 12-bit 8-channel (4 channels differential) A to D 
> converter which operates across a 3-wire interface...  You could (and 
I 
> do) read all sorts of MAPs, TPS, air/coolant sensors etc with just one 
> of those guys... >>

Several people have e-mailed me with questions about this part.  Check 
out the datasheet on the Linear Tech site:

http://www.linear.com/cgi-bin/database?function=elementinhtml&filename=DataSheet.html&name=DataSheet&num=375

Basically your controlling processor clocks over a config word which 
selects which channel to convert.  Subsequent clock pulses from the 
processor cause the A to D to convert one bit at a time of the final 
digital result.

If you want 12 bit accuracy, clock it 12 times.  If you only need 10,8, 
7 or any other number of bits, just clock it the appropriate number of 
times!

This part isn't particularly cheap, but it is rather versatile.

More later!
-Bill

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