ODB II adaptor connectivity

[paul_s]

Hi All,
I got a OSBII UART adaptor. it comes with the following cables:
Blue
Yellow
Red
Green
Based on pics I found on the website I'm assuming that
Blue is Rx (wired to Arduino’s serial Tx)
Yellow is Tx (wired to Arduino’s serial Rx)
Green should be Ground
RED should be Power

Question 1: is assumption above correct ?
Question2: the website refers to VCC pin on Arduino.
Which PIN is VCC on a MEGA and Due boards ?

Suggestion:
A simple drawing on the website wouldn't hurt...
Thank you
Paul

[stanley]

It's correct. VCC is 5V on Arduino.

[paul_s]

Thank you Stanley,

SO If I got it right, I should connect the OBD adapter Red wire to the regular 5V (out) pin of the MEGA ?
I 've read that the adapter could provide power to the Arduino.
In this case, I'd need to connect the OBD adapter red wire to the VIN pin of the MEGA?
Doing so, means it is bypassing the MEGA voltage regulator, in this case I guess the adapter provides a regulated 5V (or 3.3V on the DUE) to the Arduino ?

Thank you, Paul

[stanley]

The 5V output of the OBD-II adapter is fully regulated. So the VCC should goes to Arduino's 5V instead of VIN.

[paul_s]

Hi Stanley,

I have connected the OBDII uart v 1.2 to a VW golf from 2008.
I'm using an Arduino MEGA ADK on Serial 2 since all the other ports are already used.
I modified the OBD.h file line OBDUART Serial2 instead of Serial.

I get correct readings (RPM, speed, coolant temp). I don't get anything form Throttle ( i get a fixed value of 94 which never updates whatever I do with the accelerator).
Overall it's very slow:
when reading only 1 value I get about 3 updates per secondes.
If I try to read 4 values I get an update every 2 seconds or so.


Question 1)
Is there a way to speed things up ? I read on the website that data could be refreshed up to 100 Hz depending on car ECU speed.
I'have seen in the library that OBD speed is at 38400 Baud, can this also be increased? Any other parameter to tweak ?

Question 2)
any idea why Throttle data is not updated and value is incorrect?

Thank you, Paul

[stanley]

On a 2009 VW scirroco, the OBD-II reading interval is about 20ms. That's 50Hz. On a 2008 VW POLO, the interval is about 500ms. This depends on the response time of ECU.