I do not know that uboot would / would not damage your UART device, but I
also do not know that it will not. Then as dickelbeck mentions above there
are other potential pitfalls.
As for the Linux console, this could / should be configurable via inittab,
but uboot I have no idea exactly what needs to be done. This would most
definitely need source editing and binary recompiling.
On Wed, Mar 5, 2014 at 7:59 AM, dickelbeck wrote:
> The debug UART has both the uboot software behind it on boot, and later a
> linux serial console.
>
> During boot, if your device emits any characters, this will trick uboot
> into putting up its menu and hanging the boot process. It will be waiting
> for you to make a menu choice and your device will know nothing of it.
>
> Assuming you miss that one second window, plus all the time preceding
> uboot coming up under power where the uart's fifo will be filled, then you
> will clear uboot. But this is too much risk.
>
> The next phase of the boot has linux hosing its console output to the same
> debug port, and depending on the linux setup, you may have a serial console
> come up on that UART also. I do here.
>
> So the debug uart port is difficult to use for anything but debug.
>
> Use another UART. The device you describe may be using TTL serial, you
> did not mention RS-232 levels. This should be confirmed. If TTL, your
> device may still be at a voltage which is too high for the beaglebone to
> handle. Check the datasheet for 5V compatibility. I doubt its
> acceptable. If your device is assuredly TTL at 3.3V then it will probably
> work hardware wise by just hooking up the device, crossing TX with RX and
> tying GND to GND. The 3 wires you say. Then you have to PINMUX in the
> UART's TX and RX pins, or pick a UART you know is already pinmuxed out.
>
>
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