TTHud and a small issue..

Developer topics relating to software that logs data from ECUs

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TTHud and a small issue..

Postby dritysanchez » Mon Apr 20, 2009 11:24 pm

Morrning Gents,

i am sure you have a word to say and experience here on the forum, this is why i decided to post a new thread regarding
my application TTHud which does record the drive via webcam and applies realtime data from ecu to the video frames.

You can see the idea here: http://ttfreak.prv.pl/


Now, to the point.

I request RPM, SPEED and THROTTLE data from ecu using a packet constructed as below:

Code: Select all
 command[0]=0x69;
  command[1]=0x6a;
  command[2]=0xf1;
  command[3]=0x01;
  command[4]=0x0C;              //rpm
  chcksum=(0x69+0x6a+0xf1+0x01+0x0C)&0xff;
  command[5]=chcksum;


After this is written to ECU my receiving thread is awaitng response.
It receives the response correctly but sometimes i get totally wrong data i.e when engine is stopped - i have "4 Rpms" or if i drive sometimes it comes back with impossible value like 22100RPMs.

Below - a log from the test made few moments ago:


ENGINE STOPPED

Proper ECU response:

FOUND 0x48 [ 0x48(72) 0x6b(107) 0x10(16) 0x41(65) 0xc(12) 0x0(0) 0x0
(0) 0x10(16) ]
RPMS=((0*256)+0)/4=0
CYCLE: 5


Next query and wrong data

FOUND 0x48 [ 0x48(72) 0x6b(107) 0x10(16) 0x41(65) 0xc(12) 0x0(0) 0x10
(16) 0x0(0) ]
RPMS=((0*256)+16)/4=4
CYCLE: 6


Where did that '4' come from? Is there any checksum that you analyse before accepting the ecu response?

I am aware there is a checksum to be sent when requesting data, as my requests are being replied - but sometimes with wrong data. Hopefully i find someone here to help me out, i'm stuck with this and i thank you all for any answer...


Many thanks
Paul.



Ps. Additional data:

RPMS=((44*256)+72)/4=2834
CYCLE: 1305

RPMS=((165*256)+195)/4=10608
CYCLE: 1306

RPMS=((37*256)+89)/4=2390
CYCLE: 1307



FOUND 0x48 [ 0x48(72) 0x6b(107) 0x10(16) 0x41(65) 0xd(13) 0x5c(92) 0xdb(219) 0x0(0) ]
SPEED=92 (0x5c)

FOUND 0x48 [ 0x48(72) 0x6b(107) 0x10(16) 0x41(65) 0xd(13) 0x5(5) 0xff(255) 0x0(0) ]
SPEED=5 (0x5)

FOUND 0x48 [ 0x48(72) 0x6b(107) 0x10(16) 0x41(65) 0xd(13) 0x60(96) 0x71(113) 0x0(0) ]
SPEED=96 (0x60)
dritysanchez
 
Posts: 5
Joined: Sun Dec 21, 2008 8:42 am
Location: Kraków

Re: TTHud and a small issue..

Postby Evo4Mad » Mon Sep 28, 2009 7:45 am

Hi mate, did you figure out the problem for this? how did you fix it? I can take a look at my protocol docs if you still have some problems.
Evo4Mad
 
Posts: 332
Joined: Mon Jun 13, 2005 11:58 pm
Location: New Zealand


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