CAN, and PC connected at same time

[Neil Clayton]

I'm trying to get an inexpensive CAN dash working with the G4.  It's one of the OBD2 plugin units; and is apparently capable of CAN-BUS. No way to really verify that's what it's using (it'll do ISO9141 as well)... it works on another car; but without a scope not sure how I'd know more...   

My question is this: should I be able to run the G4 with configured CAN, plugged into the PC Link software, at the same time?

What's happening is that as soon as I plug into the RS232/CAN connector, the PC USB stops sending data to PCLink. The dash doesn't work; but before I tripple check my CAN wiring and do more digging, I'd like to know if the above scenario is normal or indicates a fault on my part.

From what I can tell I've got the CAN wiring OK: I'm seeing 120ohm across the disconnected dash unit (so its got its own termination), thus im connecting it directly to the H/L output pins of the G4.

F12 does show CAN as having errored out.  I'm a bit puzzled why, unless its due to me unplugging/pluggin in while I test.

Using ECU 4.10.2, bootcode 1.4

Board revision is: v1.2

I've included some pics to show setup:

 

[neil brown]

If serial number less than 10000 then it won't work as there is a mod requires to be done to board 

 

Link can advise

[Neil Clayton]

Seems to me it's got serial 10926 tho.... so shouldn't need the free mod

[Adamw]

The G4 ecu's dont have OBD2 capability so it sounds like it is not going to work anyway unless the dash has configurable CAN bus inputs.  OBD2 is a set of "commands", they may be transmitted by CAN or many other communication protocols, but it is nothing to do with CAN.  The G4 doesnt know any OBD2 commands, this was added in G4+ and later.

The reason your PC comms drops out will be that you have some wires connectted to the RS232 pins in the round connector.  If using CAN you only want CAN H & L pins connected.  

[Neil Clayton]

Right, sorry - I didn't mean to confused with ODB2. The dash, I assume, is using the CAN H/L of that connector.  That's what I'm trying to make use of anyway; OBD2 is only a part of this because of that physical connector.

I've disconnected the RS232, and I'm only running the CAN H/L lines from the comms connector.  I *was* previoulsy using RS232 to read from the dash, but havn't used it for a number of years now and havn't revisted that old project. At the time of writing; the RS232 connection from removed/disconnected from that same cable.

The PCLink is connected via the 2nd USB connection (red ringed connector) cable to the ECU.

 

[Adamw]

Yes, but if there are still wires connected to the RS232 pins you will lose comms, it doesnt matter if there is anything connected at the far end or not.  You can disconnect them insiode the ecu case if it is easier.  

So does your dash have software that you can configure the CAN ID's and the format and contents of the CAN messages or not?  If not then it relies on OBD2 and wont work with G4.  

[Neil Clayton]

"still wires connected to the RS232 pins you will lose comms" - do you mean, even if those pins aren't connected to anything?  They are attached to the ECU PCB @ the PCB, and go to the female (black) comms plug, but there's no electrical connection to anything RS232.   i.e: the male plug connected here has been chopped up, and only has green/white CAN lines electrically connected to anything.  I would have thought there would be no difference in leaving those RS232 lines disconnected @ the plug (male side) vs disconnecting at the ECU PCB itself.

Are you saying that I need to physically disconnect the RS232 pins from the ECU PCB? 

The dash itself is a black box, with no configuration.

It's fine if I cant get it to work with the G4, it was an experiment after all. Still, I'd like to know if I'm supposed to be able to run a CAN BUS and have my laptop also connected to the G4 while doing so (two different connectors; CAN on the black one; USB to the laptop on the red other one)