DIY-WB reading via unused input

[Dig]

--- GMECM Digest <gmecm-digest-owner at diy-efi.org> > 
> > Here's an Idea!!  hook it up to an extra PCM
> input, and have the pcm
> > table lookup the AFR(like it does volts to
> whatever for MAP, temps, etc),
> > put it in the aldl datastream and have your palm
> > pilot display it for ya.


Since everybody seems quite interested in this,
figured
I'd pass along a code patch that does the very thing.
Box is a '749, code is the $58 BBZB SyTy. 

Basically, I used the fuel pump A/D that others have
mentioned, filter it, and spit it out in the
"Commanded
AFR" field in the ALDL data. This gives you a scale of
A/D counts from 0-255 / 10. I do the math manually
from there... next phase will be to set up a LUT to
take A/D counts and re-map them to "real" AFR. This
will allow a human-readable reading on *any* scan
tool.

Usual disclaimers about blowing up you motor apply.
I actually made the mistake of outputting AFR in the
spark advance variable, could have been ugly.

In the DIY-WB tradition, this code is not to be used
for commercial purposes. I reserve the right to beat
anyone using it as such with a piece of 3/4" heater
hose that I have in my garage. 

-------------Begin Poorly commented code patch-----
Tap in to the TPS A/D read, jump to 5v A/D read
routine

Add this line:

014c0  ac bd f5 b5 97 73 86 50 7e fd 00 97 52 96 46 13


Was:
d4c6 8650                   LDAA  #$50
d4c8 bdf4b3                 JSR   GET_AD_VALUE
d4cb 9752                   STAA  AD_THROT

Becomes:

d4c6 8650                   LDAA  #$50
d4c8 bdfd00                 JSR   Additional_AD


Change AFR desired addresses in data stream:
Data displayed will be raw hex / 10.

7C0 = 01 a0
7DC = 01 a0

07c0  00 F5 00 a3 00 a5 00 a7 00 bc 00 bd 00 56 30 6c 


07d0  00 6d 00 a4 00 b0 01 7e 00 a6 00 73 00 F5 00 af 

                                        
Add filter coef  $C152 = $20.

New code with filter:
FD00:

JSR $F4B3   ; jump to A/D routine, finish the TPS read
PSH A       ; we used to hook this code in.  
PSH B       ; save it on the stack
LDAA #$00   ;load A/D channel
JSR $F4B3   ;call A/D routine
STAA $01a0  ;store in unused RAM
LDX $01a0   ;load unfiltered value
LDAB $C152  ;load the filter coef.... I use $20
JSR $F599   ;call the filter routine
STD $01a0   ;store filtered value 
PUL A       ; always PUL what thou hast PSHd, lest
PUL B       ; thy stack runneth over
JMP $D4CB   ; JMP back to where we cut into the code

FD00:
BD F4 B3 36 37 86 00 BD F4 B3 B7 01 a0 FE 01 a0 F6 C1
52 BD F5 99 FD 01 a0 32 33 7E D4 CB

----------------End poorly commented code patch-------


There is at *least* 3 more unused A/D channels, that
I can see. I've tried at least one other channel,
and it works too.

I've looked at ANHT, and it'll work for that too. The
A/D read routines are in different places, as is the
filter. You'll also have to find a different place 
for the code.

I'm guessing pretty much and '730/'749 based code will
be able to make a variation of this work. Don't even
ask me about C3 boxes... they might have something,
but I dunno where.

Notes on useability.... it's fantastic. Having real
AFR
in time with RPM and MAP makes tuning kind of a no-
brainer. 


Later,

Dig




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