[Diy_efi] Data Logger CPU schematic and C for review

Steven P. Donegan steve
Sun Feb 4 15:14:22 UTC 2007


I2C and SPI are built in on the chip I am using, CAN is not. I am
contemplating adding an external chip to provide CAN functionality. The
current design has an 8 channel D to A converter which would be able to
drive true analog gauges...

On Sat, 2007-02-03 at 22:16 -0500, Jean Belanger wrote:
> I've been following this thread with interest. Even though I don't need this
> at the moment, I'm interested to see where it ends up and I might be able to
> help at some point. Comments below.
> 
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] On
> > Behalf Of Adam Wade
> > Sent: February 3, 2007 9:39 PM
> > To: diy_efi at diy-efi.org
> > Subject: Re: [Diy_efi] Data Logger CPU schematic and C for review
> > 
> > --- "Steven P. Donegan" <steve at donegan.org> wrote:
> > 
> > > I am already doing RS-232 and LCD output logic in
> > > the data logger - we can re-use that stuff with
> > > the ARM...
> > 
> > I actually had a good idea formulate while reading
> > this.
> > 
> > Why not offer source code to make the data logger
> > optionally into a smart gauge "package"; you could use
> > the separate processor in the data logger to handle
> > measuring and displaying data from sensors etc., and
> > doing data logging at the same time, and leave the
> > processing power of the "main brain" for EFI-related
> > tasks.  Would it be reasonable to send data for gauge
> > functions through the I2C port?  I know some of them
> > today runj much faster than the original standard, so
> > it might be feasible to send a sensor "address" byte
> > and a sensor reading perhaps two of three times a
> > second.  Each sensor would have a data broadcast this
> > often.  Does that sound reasonable?  Or you could even
> > use the data logger as a "front end"; it inputs all
> > your sensor data and then sends it out over the I2C to
> > other interested parties, and you don't connect any
> > sensors at all directly to the MCU.  And then you
> > could have full display and control (perhaps useful
> > when debugging, and def. useful when tuning) on the
> > dash, while having the actual ECU under the bonnet.
> > 
> 
> I think this is a good idea but this a case where a CAN bus would be of use.
> Also, you would still need to connect any crank and cam sensor directly to
> the MCU, of course. And unless the communications between the MCU and the
> data logger can be kept well synchronized and/or very fast, you may want to
> either connect sensors such as MAP, MAF, and TPS to the MCU or keep track of
> their rate of change on the data logger and transmit that to the MCU to
> handle acceleration/deceleration fuel and spark changes.
> 
> 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.
> 
> Regards,
> Jean
> 
> 





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