by FHuettig » Tue Aug 12, 2014 4:17 am
Greetings,
As Alberto said the serial cable -should- not be required for booting, I for one have never needed it. However, I think you may be experiencing the headless equivalent of the "Parallella Perpetual Penguin Problem." This problem occurred on some boards when nothing was connected to the UART pins, and the boot process would get stuck with the two penguins displayed on the screen. It never happened when the UART RX line was pulled high by an external device. The solution was to change the boot arguments and remove the UART as the console.
I've updated the headless device tree with the changes we made to the hdmi dev-tree, and attached it here. If you are not using the UART I expect this new tree will solve your problem, copy it to the BOOT partition of your SD card, and rename it "devicetree.dtb" (extract the dtb file from the zip first!). I've tested it on my board and it seems to work, but my board didn't show the problem you describe. Please let me know if this helps, and I'll have it merged into the regular distribution.
The new devtree still includes the UART, it just doesn't assign it as the root console. If at some later point you want to use the UART as a console, you can either:
1) Switch back to the previous devtree, but then you'll again have to make sure there is always something connected to the serial pins at boot time.
2) Keep the new devtree and use agetty to re-assign /dev/ttyPS0 as a login console, you just won't get boot messages on it.
Also, I made one more change to this file, removing one of the GPIOs which was assigned as a reset pin for the USB PHY. If you are using USB devices with your headless system, please let me know if this new devtree causes problems with USB. I want to reclaim that GPIO for general use.
Cheers.
- Attachments
-
- devicetree_headless_nouart.dtb.zip
- New headless devicetree w/o UART console. Add to BOOT partition and rename as "devicetree.dtb".
- (2.31 KiB) Downloaded 1741 times
-- Fred -- Hardware Guy --