Differences between CH340 & CP210X Boards

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bitninja
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Joined: Thu Sep 15, 2016 4:09 pm

Differences between CH340 & CP210X Boards

Post by bitninja » Tue May 15, 2018 12:49 am

I have a weird situation where the only difference seems to be the serial chip and it is causing an issue when I try to get to the serial REPL.

The host PC... a Raspberry Pi running Raspbian with minicom as the terminal application.

The two test subjects are a regular Wemos D1 Mini with a CH340 chipset and a Wemos D1 Mini Pro with a CP210x chip.

Both have the same firmware loaded and when I try to connect to them the regular Wemos behaves normally... but the Pro does not seem to respond to any keyboard input. If I reset the Pro, I get the reboot message in minicom and a prompt... but still no response to keypresses.

dmesg shows no errors with either board... and besides, I'm do get output from the Pro... just no input.

I tried both boards on a Windows machine with puTTy and they both worked as expected.

Does anybody have any ideas what I might try next?

Thanks.

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Roberthh
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Location: Rhineland, Europe

Re: Differences between CH340 & CP210X Boards

Post by Roberthh » Tue May 15, 2018 5:55 am

It looks like the culprit is the Raspian driver for CP210x, or a combination of driver plus minicom sw. Try to change that, like using picocom, or python miniterm https://github.com/pyserial/pyserial/bl ... initerm.py

bitninja
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Joined: Thu Sep 15, 2016 4:09 pm

Re: Differences between CH340 & CP210X Boards

Post by bitninja » Tue May 15, 2018 10:20 pm

Good catch sir!

I tried picocom and it had no issues. So I am sure it is a problem with minicom.

Thank you for your help!

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Mike Teachman
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Location: Victoria, BC, Canada

Re: Differences between CH340 & CP210X Boards

Post by Mike Teachman » Sat May 19, 2018 2:11 am

Is there a chance that flow control settings in minicom are affecting the usb->serial device? I bring this up because in Putty I need to set flow control to None for the Wemos d1 mini. Otherwise, I see the exact same symptoms that you describe (resets to the repl prompt, but no keyboard response). Perhaps trying some different flow control settings in minicom would get it working with the Wemos d1 mini pro?

https://www.raspberrypi.org/forums/view ... p?t=109167

bitninja
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Re: Differences between CH340 & CP210X Boards

Post by bitninja » Sat May 19, 2018 4:48 am

OK, for the record, I just checked and sure enough... when I *Disabled* Hardware Flow Control in minicom it worked without a problem...
20180518_232541_small-min.jpg
20180518_232541_small-min.jpg (179.51 KiB) Viewed 60 times
I did not find any command line options to change it, but simply ran the setup...

Code: Select all

sudo minicom -s
Chose Serial port setup -> and pressed "F" to turn Hardware Flow Control to "No". Saved the settings and it immediately began to work.

Thank you, Mike!

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