Testing a PL2303 serial port adapter

[bob prohaska]

Can anybody suggest a good Mac application for testing flaky usb-serial adapter
cables under OSX 10.7.5 ? The chip is marked PL2303TA G13121E TD3733500.

I recently bought four JBtek usb-to-serial cables for use with a quartet
of Raspberry Pi 2 computers, so each Pi can be a terminal server for another.
The RPI2's are running 11-CURRENT, using ucom and uplcom kernel modules.

Initially, two of the four cables worked as expected but two intermittently
failed to connect, dropped connections or weren't recognized. At first I
blamed mistakes on my part, but after getting the bugs out of the wetware
two of the converters still consistently drop connections and aren't recognized
after that, even if unplugged and plugged back in.

The really strange thing is that if I plug the offending cables into a Mac
running Prolfic's drivers they're recognized as

6/15/16 3:13:54.000 PM kernel: PL-2303/X V1.5.1 start, Prolific

and will then work for a little while in an RPi2. After a few hours the connection
fails and dmesg reports

usbd_req_re_enumerate: addr=5, set address failed! (USB_ERR_IOERROR, ignored)
usbd_setup_device_desc: getting device descriptor at addr 5 failed, USB_ERR_IOERROR

I've requested a replacement, but the vendor is pleading "out of stock" so while I
wait I'd like to poke around a little using the Mac to see what can be learned.

The last Macintosh terminal emulators I used were Zterm and Kermit, so I need
to know what the modern choices are. Usbconfig does not seem to exist on the
Mac, are there other command-line tools that might help?

Thanks for reading and any guidance

bob prohaska

[isw]

In article <njskhi$saf$1...@news.albasani.net>,

bob prohaska <b...@www.zefox.net> wrote:

> Can anybody suggest a good Mac application for testing flaky usb-serial
> adapter cables under OSX 10.7.5 ? The chip is marked
> PL2303TA G13121E TD3733500.

IME, PL2303-based USB-serial adapters are prone to flaky behavior (when
they work at all).

I have had much better results from adapters based on chips from FTDI
(but they tend to be expensive) and Silicon Labs. Adapters based on the
SiLabs CP2102 can be found on eBay for just a few dollars. You will
likely need to install the appropriate kext for either of those.

Note that most of those adapters are used for things like talking to
Arduinos, and do *not* include the logic-inverting level-shifting stages
needed for "RS-232" compatibility. Be sure to take the inverted logic
(or not inverted, depending on how you look at it) into account when
you test them.

My favorite terminal emulator is "CoolTerm".

Usbconfig is certainly available for FreeBSD, so you could install it,
but if you have installed Apple's Developer Tools, take a look at "USB
Prober".

Isaac

[Maarten Carels]

bob prohaska <b...@www.zefox.net> wrote:

[...]> The last Macintosh terminal emulators I used were Zterm and

Kermit, so I need
> to know what the modern choices are. Usbconfig does not seem to exist on the
> Mac, are there other command-line tools that might help?

I use screen (in Terminal)

Open Termial. Type screen /dev/tty.usbserial 9600

The /dev/tty.usbserial could be different (depends on what the driver
calls it), 9600 is the speed

End with control-A control-K

Works fine with me, and no need for extra, very old programs

--maarten

[bob prohaska]

Maarten Carels <mca...@xs4all.nl> wrote:
>
> I use screen (in Terminal)
>
> Open Termial. Type screen /dev/tty.usbserial 9600
>
> The /dev/tty.usbserial could be different (depends on what the driver
> calls it), 9600 is the speed
>
> End with control-A control-K
>
> Works fine with me, and no need for extra, very old programs
>
> --maarten

Screen sounds like what I'm looking for, and conveniently screen is available both
on OSX and FreeBSD.

As it turns out the behavior of the PL2303 adapters seems to have improved markedly
after a recent software update. It does not look like the uplcom driver has changed,
but apparently some tinkering has been done on FreeBSD-ARM's USB code. The adapters
have held their connections for 24 hours, which is a considerable improvement.

For the moment I'll just keep them in service and watch, if they fail I'll try screen
instead of cu and then repeat the experiment on the Mac.

Thanks very much to all for reading and replying!

bob prohaska