For anyone interested, I spent some time chasing another failure to hibernate and/or resume under certain conditions.
Once every few days I would still get a boot failure and/or hibernate failure which also makes the ATX “emergency power off timer” drop the rails if the PC hangs during shutdown.
This type of problem is a real pain to find and initially I started looking at software and drivers.
I found that the “Ultimate DAB-FM” radio module was “now” causing a failure to suspend; more to the point, if the com Port was open when the PC went into hibernate.
I uninstalled the USB driver and reinstalled, same condition. I had recently installed numerous updates to the Win7 64 OS so I put it down to that and coded the FE to close the port prior to hibernate and on resume coded the FE to reload the Radio (if it had been playing at hibernate). This solved that problem.
Now to the “every few days” random boot failure (resume from hibernate) and/or failure to shutdown. The fault only happened in the vehicle, not on the bench, so I went looking for a power glitch (again).
USB devices can cause a boot or shutdown failure if they are plugged in or unplugged during the start-up or shutdown process, any disturbance or glitch on one of the dozen USB devices can look like a sudden disconnect to the OS.
My system has 4 separate custom microprocessor devices that communicate with various vehicle systems and each is interfaced via an RS232 to USB device. These have device drivers and I know from using them in various projects they will hang a system if not powered correctly- they can phantom power a connected device through the RS-232 data lines and will often hang if forced to do so. To overcome this problem during times when the supply to the micro regulators may be off, I secondary-power the Micro via an isolating diode from the +5 USB supply available on the USB-232 convertors.
I decided to rewire the system (again – talk about a learning curve) and in the process I wired the system to power the 4 Microprocessor devices from the PC-PSU +12v ATX line as well as +12v via the ACC/IGN switch (car battery).
It means that during cranking, the USB +5v line is not being called upon to suddenly supply extra current to the Microprocessors when the ACC voltage disconnects. These devices run perfectly from the USB supply alone and although drawing low current I wondered if the sudden (slight) transition from regulated +5v (via +12 Acc) to +4.6v USB power was causing a problem. I also got around to running ATX “+5v and common” to the front of the car via two 25A cables. This is to power 3 front USB hubs. I use 25A cable for no voltage drop and good common supply grounding.
I have not had a single boot/hibernate failure over the past week, even during all manner of abusive cranking and battery conditions since rewiring the system and reprogramming .The FE stops 2 WEB cameras (if they are recording) and now closes the DAB-FM port on hibernate or shutdown, it works perfectly.
New Layout - part of the Car-PC wiring.
As a side note, I have 8 software graphic meters programmed into the FE and watching these (for the first time believe it or not) revealed something I was not aware of or had even thought about.
This vehicle adjusts the Alternator voltage to meet the demands of current consumption in the system by monitoring current flow across a sensor “and” by interfacing with the inbuilt CPU. It knows when various lights are turning on/off and when the AC compressor kicks in/out etc.
The alternator output is 14.8 volts after cranking, after 5 to 10 minutes this drops and soon settles on around 13.4 volts. Turning the Climate control or lights on will instantly raise the output. Now this can be a problem for an AUX battery in the trunk. The system does not appear see 4 to 6 amperes drawn by the AUX battery and PC, and will drop the alternator output to 13.4v as soon as the Main battery reduces charging current sufficiently and the vehicle lights and AC are off.
With around 200mv drop across the cable to the Trunk (Car-PC “and” aux Battery both drawing current) you won’t charge the Aux battery on short trips. At the moment I make sure I have the climate control on to get over 14v to the aux battery for a period of time.
More thought needed! - If I knew what I know now this would have taken a lot less time, headaches and problem solving. Isn’t that always the case!
Smart charging systems are designed for a car in factory state, no allowance for small Car-PC’s or AUX batteries. This is a high current charging system but it won’t charge what it can’t see.
Rule1. If you are going to mount “even” a small AUX battery in the trunk and run a PC that only draws 3 to 4 amperes, run 55A cable.
Rule2. Do as OldSpark say’s on this forum! For the lowest voltage drop to any AUX battery use a relay isolator, or if an isolating Diode is needed, use relay switching across the diode.
The size of the cable is not only about current capacity, sometimes it’s all about a "very small" voltage drop, especially over a 15 foot run and even to a small boot mounted AUX battery.
The biggest problem with a complex system with a lot of vehicle interface and hardware devices spread around the vehicle is thoroughly testing it. I can’t sit there for hours trying every possible cranking scenario just to find the one that causes a problem, (batteries, starter motors and vehicles are expensive) so it’s down to the “solve it as it crops up” method. However over the past week the PC has resumed around 200 times during testing, dozens of firmware upgrades and FE code changes and run through around 30 or so engine cranks without a failure to resume.