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I am building a Yocto image for Intel Edison.
One of the image's components is u-boot with an Edison-specific patch. By default, Edison's UART port is used for u-boot console. I want to disable this feature, but only on the serial interface(u-boot also listens on USB and that needs to stay).
My main concern is the "Press any key to stop autoboot" feature on the UART port. I need this port to connect an accessory that might send something during the boot process of the main device.
How do I approach this problem? Is there an environment variable for this, or do I need to modify the sources?
Thanks in advance!
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The serial console can be disabled for a specific VM or virtual machine scale set by disabling the boot diagnostics setting. Turn off boot diagnostics from the Azure portal to disable the serial console for the VM or the virtual machine scale set.
To stop the automatic booting (autoboot) of the pre-installed kernel, send a character to the serial port by pressing a key from the serial console connected to the target. If U-Boot is stopped, it displays a command line console (also called monitor).
A universal asynchronous receiver-transmitter (UART /ˈjuːɑːrt/) is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable.
To enable the serial console for your custom Linux VM image, enable console access in the file /etc/inittab to run a terminal on ttyS0 . For example: S0:12345:respawn:/sbin/agetty -L 115200 console vt102 . You may also need to spawn a getty on ttyS0. This can be done with systemctl start [email protected] .
Setting the u-boot environment variable bootdelay to -2 disables the ability for the UART to interrupt the boot process on U-Boot 2017.01 release. It appears that -1 is a special case.
See common/autoboot.c from your U-Boot source tree for details.
About U-Boot Environment Variables
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