Chips

[James W. Swonger]

 The knock sensor is a digitally controlled analog signal processing
function block. The filters, gain blocks, etc. can be "bent" by bytes
of data written over a bus, but the output is still an analog voltage.
I suggested to them the possibility of developing a J1850 follow-on
product which would incorporate an analog I/O function, in order to
make single-wire bus compatible sensors a practical thing. This is 
certainly a doable thing, but it would take a year or so to see product
(if it even gets onto the roadmap). This device takes a standard 
sensor output and does gain, filter, window functions (it also uses
a reference channel for noise cancellation; I gather that one approach
is to put a knock sensor on each head of a V- motor and use the quiet
one as the reference for the live one on a per-cylinder basis. I'll
need to digest the datasheet a bit more thoroughly. I took a few
extras, if anybody wants to send me a SASE (e-mail me).

 From what I saw, the output of the sensor processor is an analog pulse;
I believe there is a sample/hold block on chip which can turn this into 
a DC output. At this point some sort of A-D (1 - n bits) would still 
be necessary for a digital system; an analog controlled spark advance
system could use the output as a counterweight to RPM. I was free-
associating at length, and mentioned to the Automotive guys the 
possibility that some clever lad could take this output and mate it 
to an MSD box's spark retard input and do some neat knock elimination.
I had to explain what an MSD box was; they weren't motorheads.

 I will try to find a copy of the Automotive databook and see what else 
looks interesting. I know there are injector drivers and that sort of
thing. 

 If any of you out there have specific experience with instrumenting up
automotive systems using a PC, one of the guys (the one who wrote the 
demo/control software) was interested in getting more familiar with 
the down-'n'-dirty; he has his own method, but really perked up when I
mentioned the aftermarket laptop-accessible injection controllers (DFI)
and the Turbolink monitoring hdwr/sftwr for GNs. I think these folks 
could really benefit from a few E-'rodders participating in a mutually
advantageous exchange (say no more, say no more, nudge). I will forward
contact info if desired. I have the guy's card, but he was the one 
worried about too much random E-mail so for now I'll be his mail drop.