yesss.. i have found the problem in my baudrate register:

Integer part: 103 → Bits [15:6] = 0x1A (26 in hex).
Fractional part: 0.1666667 × 64 ≈ 11 → Bits [5:0] = 0x0B.

I forgot to write the fractional part into the register. If I now write 
$1A0B, it works right away! If you stick with it long enough and read a 
lot, you’ll succeed.

Greets
Mike

Mike B. wrote:
> the UART. I've been working on it for about a week now.
> Maybe someone can help.
I'm fairly sure some measurements with an oscilloscope will do the job 
in a few hours. Do you have one?

Edit:
Forgot to send my answer, but as expected

Mike B. wrote:
> i have found the problem in my baudrate register
This problem is found within a few minutes with a scope.

Hi,

No, unfortunately I don't have an oscilloscope.
But it would be worth getting one for problems like this.
I also knew it had to have something to do with the transmission.
Even if I had been able to measure it, I probably still wouldn't have 
understood the problem.
But it's always a nice effect when it becomes clear, and your hand hits 
your head with a loud "oh no"

Greets
Mike

Mike B. wrote:
> Even if I had been able to measure it, I probably still wouldn't have
> understood the problem.
You would have found out, that the time for one bit is not 104us as it 
must be for 9600 baud.
And you would have been able to measure the clock frequency.
The only thing between those both is the prescaler.
And with all this information you would have digged in the right hole 
without spending time in trying this and that.

Mike B. wrote:
> But it would be worth getting one for problems like this.
For sure.
Debugging serial interfaces (pixel-leds, SPI, I2C, RS232, ...) without a 
scope is like driving blindly: you do not know if you are on the rigt 
way, you just recognize that somethings going wrong.

Hi Sarah,

thanks for this Information.

Greets
Mike

Mike B. wrote:
> yesss.. i have found the problem in my baudrate register:
>
> Integer part: 103 → Bits [15:6] = 0x1A (26 in hex).
> Fractional part: 0.1666667 × 64 ≈ 11 → Bits [5:0] = 0x0B.
>
> I forgot to write the fractional part into the register. If I now write
> $1A0B, it works right away! If you stick with it long enough and read a
> lot, you’ll succeed.
>
> Greets
> Mike

Same here, I was having same problem.

The USART_t.BAUD field in the USART_T struct is a 16-Bit register.  All 
you have to do is to write the calculated 16-bit value to that 
component:

1

#include <avr/io.h>

2

3

uint16_t bvalue = ...;

4

USART0.BAUD = bvalue;

It sounds like you’re dealing with advanced telecom protocols. The 
PEF20532FV1.3(https://www.ovaga.com/products/detail/pef20532fv1-3) is 
often used in similar contexts due to its robust HDLC framing and 
integrated PCM interfaces. Depending on your application, it might offer 
a simplified approach to multi-channel handling with reliable 
throughput.