Finding correct UART / Serial Console Parameters from weird output

Hi there,

I'm investigating an IKEA Uppleva Soundsystem (10224877).
Theres's an embedded linux running on Mediathek mt8551 inclusivly U-Boot.

I found a serial console header and got a readable output with 115200 8N1 params. Unfortunatly I was'nt able to break the U-Boot autoboot by pressing any key.
The output ends with "Uncompressing Linux... done, booting the kernel."

I found also a second header with 4 Pins and 3,3V. I assume it's a further serial port. A while after "Uncompressing Linux... done, booting the kernel." from the other serial port comes a last message over this port.
Unfortunatly I can't read it.

So some things speak for it that it's a serial port with other messages than on port 1.

My question now, can someone tell me how to interprete/decode the output? E.g.: 115200 8N1

\0xe3\0xf4\0x15\0xaa\0xe6\0x036\0x1a\0x00\0x00\0x01\0xe6\0x036\0x1a\0x10\0x00\0x01\0xe6\0x035\0x1a\0x00\0x00\0x01\0xe6\0x00\0xe1\0x1a\0x00\0x00\0x01\0xe6\0x00\0xe1\0x1a\0x10\0x00
\0xe6\0x03u\0x1a\0x00\0x00
\0xe6\0x8c\0x05\0x02\0x00\0x00\0x00\0xe6\0x01o\0x1a\0x00\0x00
\0xe5\0x90\0x1b\0x04\0x01\0xe6\0x01o\0x1a\0x10\0x00
\0xe6\0x03u\0x1a\0x10\0x00
\0xe6\0x03t\0x1a\0x00\0x00
\0xe6\0x03s\0x1a\0x00\0x00\0x10\0xe6\0x03s\0x1a\0x10\0x00\0x10\0xe6\0x03r\0x1a\0x00\0x00\0x10\0xe6\0x03r\0x1a\0x10\0x00\0x10\0xe6\0x03t\0x1a\0x10\0x00\0x10\0xe7\0xe8\0xd6\0x000700\0xe7\0x80\0x00\0x006K- \0xe7\0x80\0x00\0x000201\0xe6\0x035\0x1a\0x10\0x00\0x11\0xe3\0xd0:\0xaa\0xe3\0xd0;\0xaa\0xe7\0xd0[\0xea\0x00\0x00\0x00\0x01\0xe7\0xd0[\0xea\0x00\0x00\0x00\0x11\0xe3\0xf4 \0xaa\0xe6\0x03s\0x1a\0x00\0x00\0x11\0xe6\0x03s\0x1a\0x10\0x00\0x12\0xe6\0x03z\0x1a\0x00\0x00\0x12\0xe6\0x03z\0x1a\0x10\0x00\0x12\0xe6!\0xd8\0x1a\0x00\0x00*\0xe6!\0xd8\0x1a\0x10\0x00*\0xe7\0xf0"\0xea\0x00\0x00\0x00\0x08\0xe8\0xe0\0x02\0xca\0x00\0x00\0x00\0x00\0x00\0xe7\0xf1\0x00\0x006K- \0xe7\0xf1\0x00\0x0002T0\0xeb\0xe8\0xb9\0xfa\0x00\0x15\0xbb\0x00\0x01\0xe0\0x00\0x00\0xe4\0xf40*\0x02\0xe6\0x03R\0x1a\0x00\0x00*\0xe7\0x80 \0x00\0x01\0x01\0x00\0x00\0xe6\0x03R\0x1a \0x00+\0xe3\0xf8\0x02\0xaa\0xe5\0xf8\0x04j\0x00\0x00\0xe7\0xf8\0xa6\0x00NORM\0xe3\0xf9p\0xaa\0xe3\0xe8\0xbc\0xaa\0xe7\0xe8\0xd6\0x000700\0xe7\0xe8\0xbd\0x006K  \0xe7\0xe8\0xbd\0x000201\0xe7\0x8b\0x14Z\0x00I\0x00{\0xe7\0x8b\0x14Z\0x00{\0x00\0xad\0xe6\0x039\0x1a\0x00\0x00\0xad\0xe6\0x039\0x1a\0x10\0x00\0xad\0xf0\0x91\0x00\0xcf\0x00\0x00\0x00\0x06\0x00\0x00\0x00\0x11\0x00\0x00\0x00\0x00\0x02\0xf0\0x91\0x00\0xcf\0x00\0x00\0x00\0x00\0x01\0x00\0x00\0x11\0xc0\0x00\0x00\0x00\0x02\0xe4\0xe8]*\0xa1\0xe9\0xe8\0xdfz\0x00\0x04\0x00\0x00\0x00\0x00\0xe8\0xe0\0x02\0xca\0x00\0x00\0x00\0x04\0x11\0xf0\0x91\0x00\0xcf\0x00\0x00\0x00\0x14\0x02\0x00\0x00\0x11\0xb8\0x00\0x00\0x00\0x02\0xe6\0x03:\0x1a\0x00\0x10M\0xe6\0x03:\0x1a\0x10\0x10M\0xe8\0xe0\0x02\0xca\0x00\0x00\0x00\0x07$\0xe4\0xe8]*\0xa1\0xe4\0xe8]*\0xa1\0xe4\0xe8]*\0xef\0xe6!|\0x1a\0x00=\0x12\0xe6!|\0x1a\0x10=\0x12\0xe4\0xe8]*\0xa1\0xef\0xe8K\0xfe\0x12\0x00\0x00\0x00$\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0xef\0xe8K\0xfeZ\0x00*\0x00\0x00\0x00\0x00\0x00\0x80\0x00\0x00\0x00\0xef\0xe8K\0xfe\0x12\0x00\0x00\0x008\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0xef\0xe8K\0xfeF\0x00\0x00\0x00\0x00\0x00\0x00\0x02\0x00\0x00\0x00\0x00\0xe4\0xe8\0xf2*\0x00\0xef\0xe8K\0xfeZ\0x08*\0x00\0x00\0x00\0x00\0x00&\0x00\0x00\0x00\0xef\0xe8K\0xfe\0xa4\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0x08\0x08\0x00\0xf3\0xe8\0xde\0xff\0xa4\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0x00\0x08\0x08\0x00\0x00\0x02:\0x02

Thanks for any help!

Originally Posted by szsoftware Theres's an embedded linux running on Mediathek mt8551 inclusivly U-Boot. I found a serial console header and got a readable output with 115200 8N1 params.

What are you connecting to those serial port pins?

I had a similar problem reading from the serial port of an MStar SoC. (FWIW MStar later merged with MediaTek in 2013.)
Neither an FTDI USB cable (a real one, not a cheap knockoff) or a Sparkfun converter could produce a readable RS-232 signal from the 3.3V serial data. Measured on a scope, the serial data was on the slow side of 115200 baud (i.e. the bit times were slightly longer), and the rise/fall times looked long/slow.
Eventually a real 3.3V to RS-232 level shifter IC finally produced a readable signal.

I recommend that you use a converter that incorporates a Maxim MAX3232 chip or similar, e.g. ICL32x2 or ADM32x2.

Regards

Hi there!

I use a "10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light" as I do to connect with all my embedded devices and routers laying around :-).

I measured approx. 3,3 V at the pins and the behaviour of how (weird) characters come on the screen indicats me it must be something like messages.

As I said, on the one Port I can read everything.
On the second I tried all usual speeds.

So, following what you say my levelshifter/uart converter may is not good enough/not tolerant enough to decode the (buggy) signals of the embedded device uart2 port?

Thanks for you interest and help!

Sven

Originally Posted by szsoftware So, following what you say my levelshifter/uart converter may is not good enough/not tolerant enough to decode the (buggy) signals of the embedded device uart2 port?

What I said were my factual experiences of what I found to work or not work.
The suitability of your converter will only be determined after this issue is resolved.

I found also a second header with 4 Pins and 3,3V. I assume it's a further serial port.

If you're that confident in your choice of converter, then test your assumption that this is a serial port.
Make sure you're not looking at a differential signal(s).
Use an oscilloscope to confirm the character framing and measure the baud rate.

Regards