[Diy_efi] Data Logger CPU schematic and C for review

Bernd Felsche bernie
Mon Feb 5 02:33:57 UTC 2007


On Monday 05 February 2007 10:36, Steven P. Donegan wrote:
> On Sun, 2007-02-04 at 16:44 -0600, Robert W Hughes wrote:
> > >> What would also be interesting would be the ability to
> > >> directly

> > >> > drive analog gauges. Since a lot of people lose some or all
> > >> > of the dash gauges when going to a non-OEM MCU, it would be
> > >> > nice to be able to restore this functionality. I don't know
> > >> > exactly how this would be done and it certainly is
> > >> > dependent on the vehicle but some type of PWM or stepper
> > >> > motor controller would cover some cases.

> > > I've toyed with the idea of using RC-servos to do the needle
> > > positioning on stock gauges. The servos are controlled by
> > > pulse width and (I understand) will lock when they get no
> > > further signal.  Even removing power leaves the servo locked
> > > in position.

> > > This by-passes the need to fake various types of signal and
> > > allows for other interesting analogue gauge functions to be
> > > programmed.  Also, pulses only need to be sent to the gauge
> > > when the indicated value is to change.

> > Most late model cars use air core meters which can do 90 or 270
> > degree or more sweeps. Check out the Phillips driver SA5778D at
> > http://www.ortodoxism.ro/datasheets/philips/SA5778D.pdf  for an
> > idea of what is involved. This chip accepts a serial bit string
> > to drive two 90deg meters and one 270 with .35deg resolution and
> > could probably drive the instruments in a car panel with
> > whatever you wanted to digitize and send out. I think most
> > manufacturers are using something like this in their panels now
> > to cut down on wiring and connector pin count.

> Thank you for the pointer - I may add the device to my design...

Perhaps better to focus on CAN aspects of the logger.

A separate CAN-based display module can then display any interesting
quantities that may be made available via the CAN properties of the
logger. Several and different CAN display modules can indeed be
connected the the same network as the logger without changes to
logger software or hardware.

-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | "If we let things terrify us,
 X   against HTML mail     |  life will not be worth living."
/ \  and postings          | Lucius Annaeus Seneca, c. 4BC - 65AD.






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