Strange problems with CH340G (uchcom)

[Bernd Walter]

I tried to flash an ESP8266 with the onboard CH340.
The same board works fine when I use a CP2102 instead of the CH340.
Flashing requires a python tool, which sends a SLIP encoded request
and expects a SLIP encoded response with 115200 at 8n1.
The read function however times out receiving the response without
getting a single byte, even if I add a high delay between sending and
reading.
The strange thing is that I can see a valid response on a scope just
a few µs after the request completes, while the receiver don't even
see the first byte.
If however I physically loopback the CH340 it receives it's own request
just fine.
Two CH340 xconnected work fine too.
Same when I xconnect a CH340 and a CP2102.
Now I'm completely out of ideas, why the python tool has problems
to see the response data with the CH340.

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.