[Diy_efi] Traction control strategy (solution offered)

[Nic van der Walt]

> The second paragraph there describes using the AVR to measure pulse
widths.
> Is this what you are referring to? We are currently running Windows
based

Almost. It will be a good base to work from. You want the AT90s8515 or
8535.
Main difference is that you don't want to measure the pulse width in the
interrupt,
but rather timestamp the leading edge, exit the interrupt routine and
then when
you get the next interrupt check how much time has passed.

The 8515 has three interrupt lines (two "real" and a comparator you can
use as one).
This will allow you to easily measure two driven and one non-driven
wheel. With a
bit of external logic you can measure all four wheel sensors.

>machines... but we can easily write the program as a Console
application in
>C/C++ (dos) which is what were had planned on doing anyways. So if we
use

Console is still windows, i.e. no direct access to the parallel port,
and no timing.

> the AVR, we can simply read the datastream from the serial port
correct?

Yes. Accessing the serial port is easy. For delphi there is a couple of
free and
reasonably good components to do it. When you get there I can send you
sample code.

> I'm assuming we just take the output from the LM339 and send them to
the AVR.

The hardware will be:

1) Convert sensor signal to square wave.
2) Connect square wave to AVR.
3) Power supply for AVR (5V , well regulated). LM7805 with proper
protection and a lot of caps will work.
4) RS232 level conversion. AVR outputs 5V (ttl) RS232, PC needs -12v to
+12v RS232. Use MAX232A.
5) Some logic if you want to measure all four sensors.
6) Some why of retarding/cutting spark or fuel.

> using the AVR simplies everything in
> communicating the ABS signals to the PC via the serial port.

Yes, although you will find that once you have the AVR running it will
be easy to but the whole shebang in the
AVR and just use the laptop as a display and accurate speedo!

I'm swamped until the end of the week, but I might be able to draw up an
accurate block diagram over the weekend.
This project will be open source and freely available, right?

N.



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