
The speed at 115k2 Serial is maybe 10x faster than the one via USB.
With the same code sending chars (via Serial.write(byte);).
Can somebody confirm?? (Updated the TEK demo sketch with elapsed time measurement).
PS: to draw the TEK demo screen takes
4998 msecs via USB
433 msecs via 115k2
108 msecs via 460k8
63 msecs via 921k6
If you send long strings it goes much faster.
I thought this had been investigated and the issue partially lies with the host driver.
Your serial USB adapter probably uses its own driver.
FYI: I tested the “USB read speed” with help of PaulS benchmark and I get ~230kB/second (the F103 reads data from PC via Serial.read()).
That is consistent with his measurements with Maple.
We use window’s built in CDC ACM driver
BTW. I’m saying there are no bugs, but please see if you can find the other thread about this, because it has been discussed at length in the past.

In other words, the window’s built in CDC ACM works 9k6 when receiving bytes via Serial.write() from F103..
BTW, the window’s built in CDC ACM works 2.3Mbit/sec when sending bytes to F103 (F103 receives them via Serial.read() in a loop)..

4998 msecs via USB -- OLD CDC ACM driver
433 msecs via 115k2
108 msecs via 460k8
63 msecs via 921k6
61 msecs via USB -- NEW CDC ACM Steve's patch
Is there another PR that I need to merge ?
As I can see, this commit should have solved the USB speed issue.
Pito, which core/files did you test?
I did not test any PR, I only complained on USB TX performance and applied your patch then manually..
My local libmaple repo is old.
In this case please remove libmaple from the title.
So this has been fixed ages ago
Its because @Pito was using a fairly old version of the repo.
I guess this is something we should also everyone when the report a bug, i.e “Are you using the latest version of the repo”
PS. I changed the thread title to show this is solved