@optech Depending on the higspeed mode used, the MT7688's UART may not be very precise at high baud rates. If you have a look at the MT7688 datasheet on page 157ff, you see that for 115200 there's a divisor of 14 (down from 26Mhz) for the UART clock (which is divided by 16 to get to the baud rate) when highspeed_mode=0. So the effective baud rate you'd get is 26E6/14/16 = 116071. I don't know what mode is used in uboot (and linux tty driver, for that matter), but I would not be suprised if it was the simple non-high-speed mode. Apparently, FTDI chips (I only use those, because of no driver hassles for those on macOS) are a bit more tolerant than others to inprecise baud rates. So I never experienced this in my daily work (I have >1000 Omega2 based products in the field). However, for a project I had to calculate the exact sending time for a byte stream @ 9600 baud - which turned out to need adjustments exactly due to not quite precise baud rate…

@francisco-vieira I agree with @crispyoz, this sounds like a handshaking issue - my guess is in hardware. To check on this, you can use the devmem command to read the UART0 status registers. I would start with the Line Status and Modem Status registers. See the MT7688 datasheet for more info on the registers, and run devmem --help on the command line to see how to read the registers.

@Lazar-Demin No: for size, cost, and power reasons we need to use the built-in UART(s). I'm interested that @luz is having no trouble doing basically the same thing. It would be nice to know what he/she is doing that is different from what I am doing. I will rebuild buildroot and see if this makes a difference.

@john-frailey said in Change Serial Console on Boot to ttyS1: I've got an environment setup on a io board , that I would like to switch the linux console port from ttyS0 to ttyS1. I wasn't sure if that is done in /etc/inittab or in one of the system config files ? I have an omega2. I'm not sure how Oninon's kernel does it, but in Mediatek's, Linux detects which UART U-Boot activated and uses that. You could override this in the kernel if building it from source - I had to as I turned on a second one in a custom U-Boot, and Linux was then not using the one I wanted.