[BRLTTY] Focus 1 70 display and USB to serial adapter: possible connecting this scenario?

[Hammer Attila]

Hi Dave,


This is probably the problem, I'll definitely try it.
What is the value in MS that you think doesn't cause too much latency 
for Focus displays, whether it's a connection happens a traditional 
connection or operation via a USB converter (using a USB to serial 
converter)? What the maximum value this code line related with accepts 
the driver?

What is the basic operation? For both connection types, does the current 
driver constantly try to establish a connection, or does it wait for 
e.g. 50 or 100 milliseconds before trying again?

So, me need playing the best latenci time in milliseconds to determine 
the best wait time.

But real serial hardvare connection why not happens this issue, or 
happens, but not possible detecting this with user level because more 
faster the driver establish the connection a traditional serial cable 
between the real serial port and the display serial port?

I'm simply interested in the difference in operation between the two 
types of serial connections. I'll definitely report back if I achieve an 
encouraging result.

The 200 millisecond time is not too big time, only me need knowing what 
the maximum value with safe drive detection working related if the 200 
MS value is too small based the testing experience.

Thank you for your log analysis and suggestions, again we stepped 
forward this issue related,


Attila


2024. 12. 24. 14:52 keltezéssel, Dave Mielke írta:
> [quoted lines by Hammer Attila on 2024/12/24 at 13:52 +0100]
>
> I think that we shouldn't trust the stty -a information for when it isn't working because, in that state, the driver is mostly not started. In other words, it starts, finds out very quickly that it won't work, and then stops. It then stays stopped for several seconds so what we're likely seeing is the state of ttyACM0 when the driver isn't running.
>
> We know that the Focus is working, that brltty is working, that the adapter is working, and that the adapter's baud can be set (via stty and screen). In other words, we know that all the pieces seem to be working. I'm thinking, therefore, that we maybe need to add a delay after the driver opens and configures the adapter before it starts writing to and reading from it.
>
> Look for this line in Drivers/Braille/FreedomScientific/braille.c:
>
>     684: descriptor.serial.parameters = &serialParameters;
>
> Try adding this line right after it:
>
>     descriptor.serial.options.readyDelay = 200;
>
> If you're curious, that value is in milliseconds.
>
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