G3 running G4 firmware - CANBUS settings (offset, scale)

[Hiney]

Hey,

I'm working on an Arduino project to display ECU values from the CANBUS to a display. I have captured some data and now trying to convert that to the correct values but i am unable to find any info on the scale and offsets. The settings window i have is not the same as others, i'm guessing due to age, so i cannot configure the parameters myself.

I'll attach images of the PCLink screen i have and the CANBUS

Edited February 28 by Hiney
uploading pictures

[Confused]

I would consider looking at getting the ECU to send out the Generic Dash stream - all the frames, values and offsets for this are in the Help file.

This might help give you some ideas on scaling and offsets too. Remember that values it will be in metric, so kPa, not PSI, Celsius not Farenheit.

[Vaughan]

Downloading and installing G4+ PCLink and looking at the test calculator in the CAN Setup window should give you a good starting point. You can also figure it out if you have some known values in the ECU and matched values from the CAN message.

[Hiney]

13 hours ago, Confused said:

I would consider looking at getting the ECU to send out the Generic Dash stream - all the frames, values and offsets for this are in the Help file.

This might help give you some ideas on scaling and offsets too. Remember that values it will be in metric, so kPa, not PSI, Celsius not Farenheit.

Thanks for the reply. The reason I limited the output is so i can try and figure out what is what from a smaller amount of data. Am i correct in assuming that each of the ID's will be an individual value? so for example ID 064 is showing the ignition angle data.

2 hours ago, Vaughan said:

Downloading and installing G4+ PCLink and looking at the test calculator in the CAN Setup window should give you a good starting point. You can also figure it out if you have some known values in the ECU and matched values from the CAN message.

THanks, I have looked in the g4x software but its offering setupvalues. I'm trying to understand the values using this online calculator

[Vaughan]

45 minutes ago, Hiney said:

THanks, I have looked in the g4x software but its offering setupvalues. I'm trying to understand the values using this online calculator

G4X won't help as it doesn't have hardcoded multis and offsets like G4+ and older do. I've attached an image of how the Test calculator in G4+ works.

In terms of determining which data is where in the CAN stream you could do things like force the temps and map into fault and then change their fault values one at a time to figure out where they are in the message. G4+ Test calculator does also specify the number of bits the value is in the ECU which probably directly translates into the G4 CAN stream as well (i.e. Ign Angle will be 2 bytes)

[Adamw]

On 2/29/2024 at 11:38 AM, Hiney said:

Thanks for the reply. The reason I limited the output is so i can try and figure out what is what from a smaller amount of data. Am i correct in assuming that each of the ID's will be an individual value? so for example ID 064 is showing the ignition angle data.

G4 doesnt have configurable CAN format, you can only load one of the preconfigured LCS files.  

The one you have shown in your screenshot is the racetechnology stream which uses a standard single frame type message (called sequential in G4).  All data is sent as 16bit values.  So in this example a single frame will be sent out using ID 100 (0x64) the first two bytes will be IAT, Bytes 2&3 will be ECT, bytes 4&5 will be MAP and bytes 6&7 will be Ign angle.

If you load the generic dash stream, this uses a compound message format (sometimes called multiplexed), this sends all data using just one ID, by spreading the data over multiple frames, Byte zero has a "Frame ID", byte 1 is empty, then byte 2-7 contain the three 16bit channels fo data.

This is explained in more detail if you click the help button at the bottom of the CAN setup screen.  

The content and layout of the Generic dash stream is also shown in the help file page: G4 ECU Tuning Functions > CAN > Device Specific CAN Information.

I have attached a DBC for the generic dash stream for your info, the lambda/wideband scaling will be different in G4 but the rest of it should match I think.  
 

 

Generic Dash.dbc