On 01/07/2020 09:08 AM, Johann Klammer wrote:
> 
> I did scope the output again and observed a tau of 23 uS.
> (=baud rate err of 0.11) Is this too much?
> Because I still can't get the uC to respond..
> 
> 
Nah user error again. is closer to 25uS...

On 01/06/2020 02:13 PM, Johann Klammer wrote:
> $ stty -F /dev/ttyUSB0 ispeed 38400
> stty: /dev/ttyUSB0: unable to perform all requested operations
> $ stty -F /dev/ttyUSB0 ispeed 38400
> (this one succeeds)
> 
> 
may have been a user error.
$ stty -F /dev/ttyUSB0 38400
works at once.

I did scope the output again and observed a tau of 23 uS.
(=baud rate err of 0.11) Is this too much?
Because I still can't get the uC to respond..

On 01/06/2020 01:33 PM, Johann Klammer wrote:
> Oh, and scoping the output shows that the actual rate is at least 1MBaud
> (the narrowest pulses are around 1uS wide.)
> 
> 
ok. seems it's not the actual number that matters, but the number of invocations. 
It's some internal state that changes.

$ stty -F /dev/ttyUSB0 ispeed 38400
stty: /dev/ttyUSB0: unable to perform all requested operations
$ stty -F /dev/ttyUSB0 ispeed 38400
(this one succeeds)

Oh, and scoping the output shows that the actual rate is at least 1MBaud
(the narrowest pulses are around 1uS wide.)

stty -F /dev/ttyUSB0
speed 0 baud; line = 0;
min = 1; time = 0;
-brkint -icrnl -imaxbel
-opost
-isig -icanon -iexten -echo

(something is wrong)

stty -F /dev/ttyUSB0 ispeed 38400
stty: /dev/ttyUSB0: unable to perform all requested operations

But if I give an obv wrong value it doesn't complain.
stty -F /dev/ttyUSB0 ispeed 3840


The dongle is a
FTDI Chip
TTL-232R-5V
USB to TTL Serial Cable(5.0V)-1.8m (2419945 at Farnell)

On Linux kernel Version 3.14.15

I guess since the're the monopolist 
they don't have to produce working hardware anymore.

And yes, I've read the crap about read write access on stackoverflow. 
I am in the plugdev group and it's read/writable for plugdev.