no vehicle speed

[FoxSTI]

^ They probably dont have it. My guess is if they did they would have offered it to me already.

[FoxSTI]

for some reason the guy I have been talking to or e-mailing with thinks I need to go a shop and is really not wiling - or it seems - to answer my questions. Maybe he is just really busy.

I really hope this works - I think it should !

[FoxSTI]

Dave ,

Thank you for you help. This did the trick. Vehicle Speed now gets a signal and a value.
The STI had a digital speed readout. The C125 is off by 1 mph. It is slower. it also only measures speed up to 77 mph. then it starts to count negative and backwards (which throws off my gear calcs.)

I am going to call MoteC and see if they can help me with that in the meantime.
I am very thank you full for you taking the time to assist me.

[David Ferguson]

Well that's an easy one to fix.

According to the wikipedia ODBII PID page, the Vehicle Speed is returned as a one-byte value in km/h.

To fix this:

-- Use the C125 Dash Manager to open the Communications Setup (menu Connections->Communications...)
-- Select the "OBD Service 01 Reply Comp" template and click the "Edit..." button.
-- Click the "Received Channels" tab, and select row 2 of the identifiers list (the one with ID = 010D).
-- With the "Vehicle Speed" channel selected on the list on the right, click the "Change..." button below the list.
-- Untick the "Signed" option. This is why your values turn negative above 128 km/h (about 80 mph).
-- Click the OK button to close the Change Comms Channel window.
-- [optional] You might want to save this modified template in case you were to use it in another config -- I would overwrite the same name "OBD Service 01 Reply Comp".
-- Continue clicking OK to close all the windows and then transmit the configuration to your dash and test.

[FoxSTI]

David I will try when I get home.
this is all very interesting. What does the signed option actually do - why 128 kph?

By the way, when looking at boost, I can only see Positive values, can I use the signed option to see vacuum or is that something else?

[adrian]

It looks like there is a an error in the template, Vehicle Speed should be unsigned as David has said. I have logged it as a bug and will get it fixed. I will also review the transmit template as Vehicle Speed is probably more useful than some of the other ones set up by default.

A signed number is simply a number that can be negative and positive. The most significant bit of the channel is used to tell you whether the number is negative or not. This means that the overall positive range is halved. So for example a signed 8 bit channel has the range -127 to +127 and an unsigned 8 bit channel has the range 0 to 255.

OBD-II doesn't transmit boost pressure, only Manifold Absolute Pressure which is always positive. You could create a table that converts this channel to boost pressure so that you get negative values when MAP is below 100kPa.

[FoxSTI]

Thanks.
So anytime I select "signed" the dash will take the left most digit and allow it to be negative by spiting it in half.
This is all very interesting.

Too bad the software help file does not cover much in detail about some of the options.
For instance I want to read O2 Left.

So I made sure I am requesting it. when I add the channel in the "compound Message Identifier" I am promted for an OFFSET and IDENTIFIER MASK - along with the ID which in this case is 0114.

What are those two values?
Also when I am configuring the response channel I see:
What is Offset and Mask? The Mask value seems to be a hex number right? converted to decimal 65,535.

I am also guessing that Multiplier 5, Divisor, 1 Adder 0 will essentially be applied to the data received from the channel. ?

[adrian]

Yes, the most significant bit simply tells the dash whether the value is negative or not.

If you want to learn more about CAN and how to set up the templates in the dash have a look at our webinars on CAN. They can be found here: http://motec.com.au/webinars/webinararchive/