I’m in process of getting our CANTCU/8HP installed and running into an issue where the GPS module is causing some interference with the shifter.
Setup is Motec ECU, ADU, PMU, GPS, CANTCU all on the same Bus (Car has been running for 2 years without the CANTCU) When we first installed the CANTCU the GPS module was out of the car for maintenance (the internal battery broke off the board) everything seemed to be working fine until we reinstalled the GPS module. At that point, we ran into issue that the car wouldn’t even start. We determined that the CANTCU and GPS were both on base address 400. So “easy fix” I changed the GPS address to 450. At this point the car would start but could not select a gear.
As I implemented new code across ADU, PMU and CANTCU, I was chasing circles until determining that when the GPS was plugged in I could not select a gear.
After troubleshooting determined that unplugging the GPS would immediately allow a gear to be selected. But very WEIRD, after the initial gear selection, you can plug the GPS back in and shifting works as expected until the transmission is power cycled again. Actually I think it was until the main power was cycled, not just the transmission.
Is there some other “base address” message in the GPS that I’m missing? Anyone seen any issues like this? Or have any thoughts?
You can use Light Client with your USB to CAN device to monitor all the messages on the bus. Might be worth powering up with and without the GPS connected and seeing if there’s anything unexpected?
The GPS is not sending only the 0x400 ID.
It’s sending 5 frames, from 0x400 to 0x404.
The IMU also has a separate high-rate output with default IDs 0x408 and 0x409.
Disconnect the GPS from the network.
Log the CAN bus with the Light Client.
Start with everything powered off, and then switch it on.
You will see a list of all CAN bus IDs sent on the bus during that time.
You need a sequence of 5 unused IDs in a row so you can assign the GPS to them.
I had changed the GPS to 0x450 but still had the same issues. I also tried 0x320 and saw the same problem.
I did look at Light Client and did not notice any conflicts. The CANTCU has a built in BUS monitor also, but I didn’t realize that until after I left the shop, so I’m going to look at that today.
I’m sorry for not knowing, but what is the IMU? Can those address be changed? Or does that change with the Base address? The CANTCU is Base + 11 or 12, so those would certainly conflict.
From that I would presume that changing base to 0x450, then the IMU would be at 458 and 459?
Our situation is Odd that the shifter will begin working if the GPS is unplugged and seems to continue working after it’s plugged back in. But it will not work if the GPS is initially plugged in.
I’m going to look at the CANTCU sniffer today to see if it’s seeing something else.
After additional troubleshooting and using the CANTCU Can Monitor/logger I found that the issue also occurred if I had our steering wheel disconnected (custom CANBus wheel) when everything was powered up. Once powered up I could plug it in, start the car and shift fine.
I ran the log files through Claude who said the BUS was crashing out when the wheel was plugged in, GPS remained plugged in the entire time, but I assume the same would have happened there.
The wheel has a switchable terminator that was OFF. I tried with it switched on and all plugged in and things worked as expected. Claude reported that the BUS was no longer crashing out.
I’m not sure what changed on my BUS from original build, but I recently removed a resistor/terminator to bring the resistance from @38ohms to @60ohms, but I think the wheel terminator put it back to the 38ohm range.
Need to dig in and figure out where all the terminators are. I think a module that was added must have a built in terminator that I’m not aware of.