Hi,
okay, I took the time today to look a bit at the stability issues we have. I didn't do any analysis, just tried different boards with different setups and wrote down what happened.
The analysis should happen when I visit Nikolaus with all the PCBs and various AC Adaptors and USB cables.
@Nikolaus: But of course, if you want me to run any other tests upfront, let me know.
First, here are some general things I found out:
* The Micro USB cable matters! I've got a MicroUSB cable that, when connected to the Pyra, is not able to boot it. All I get is a short blinking of lights and then a reboot. The cable itself works fine for any other device (I use it to charge my smartphone each night) and also works fine as data cable (I used it in the tests to connect the FTDI to the laptop)
* The same thing applies to the AC Adaptor: Some AC Adaptors work, some simply cause the same reboot loop. So to get it to boot a proper combination between an AC Adaptor and USB Cable is needed.
* Even with a proper cable, the USB port seems to be VERY unstable. Just touching it or wiggling a bit can cause a freeze on the Pyra!
* When inserting a battery, the Pyra sometimes boots up immediately and sometimes it doesn't. No idea when it does what and why.
* I didn't have a single freeze at MLO even though I always had the SD Card in the slot already when I connected the power. So that issue Nikolaus had cannot be confirmed here (which is good :))
Okay, so much for the general info. Now take a look at the attached Excel sheet. These are some results I got from booting various boards under different setups. The display board I used is one with the SSD included.
Here is a summary of the results:
* Booting without a display board attached almost ALWAYS works fine. Except for the first one or two tries. Regardless of whether I boot with an AC Adaptor, a battery or both.
* Booting WITH a display board attached makes the whole thing very random. Often the board boots up fine but doesn't find the display board. This especially seems to happen when only powering from a battery.
* Booting WITH a display board but without battery causes the Pyra to shut itself off when X is loading and the display should show something. This happens regardless whether my laptop or a 2A USB AC adaptor is used to power the unit. If the display board is not found, it doesn't shut itself off.
* Booting WITH a display board and powering ONLY from battery works stable (once you managed to boot it, as most of the times it doesn't find the display board, as mentioned above).
* The best combination seems to be booting WITH a battery AND an AC Adaptor connected. In that case, it finds the display board most of the time and also doesn't shut off when it's booted up. However, in case the battery is removed while AC is still being kept connected, the Pyra shuts off after a few seconds.
What does that tell us? I'm not sure. I doubt the LCD Cable itself is flakey, as it hasn't been touched during the reboots and once it found and initialized the display board, it worked stable.
But as it mostly works if both the battery AND the AC connecter is attached, it could be some power issue. Maybe at bootup, when the kernel initializes the hardware, the display board lacks the power to respond and therefore it's not being found?
It's a bit of a mystery, but the more power I pump into the system, the more stable it seems to run and find the display board as well.