Re: USB-serial adapter suggestions needed

Okay you all, where should all this great info go in the docs?

--
Joseph Holsten
http://josephholsten.com
mailto:joseph@josephholsten.com
tel:+1-360-927-7234

On Sun, Dec 24, 2023, at 11:39, bob prohaska wrote:
> On Sun, Dec 24, 2023 at 06:01:00PM +0100, Bernd Walter wrote:
>> If you see ssh connections drop then this is network related and has nothing
>> to do with the USB adapter.
>> In case an USB adapter fails you will just drop out of tip into the shell.
>> Most likly this is a statefull network device - e.g. NAT expire on either
>> your or ISP side.
>> TCPKeepAlive is active per default on OpenSSH, but often not enough for some
>> agressive ISP equipment.
>> You might also want to check if you have local firewalls in between, which
>> are misconfigured to expire TCP states too early.
>
> The normal network setup is shown at
> http://www.zefox.net/~fbsd/netmap
> SSH sessions are initiated from the Pi4 workstation on the LAN to each
> FreeBSD host, using tip or cu to connect to the corresponding Pi's serial
> console. 
>
> It's maybe worth mentioning that changing the host named pelorus from
> WAN to LAN and booting release/14 seems to make no difference. SSH sessions
> not involving usb-serial adapters stay up until the WiFi link crashes for
> some reason. According to the router's (D-Link DI-524) control panel the
> firewall features are turned off.
>
>> If you run through equipment, which isn't in your hands at best you have
>> an OpenVPN or similar connection to handle network instabilities and run
>> ssh on top of it.
>> 
>> If however this is not ssh session dropped and just tip, then look up kernel
>> messages if the USB adapter was disconnected.
>
> There are no messages of the kind seen when an adapter is unplugged or
> turned off using usbconfig. I've tried turning on usb debugging, but the
> output is not obviously related to the disconnects, in part due to volume.
> Interestingly, a "stuck" adapter can usually be "unstuck" by using usbconfig
> to turn the power off and back on.
> 
> Prompted by your email, I noticed that under the Advanced > Filters page of
> the router there's an option called "IP Filters", said to deny LAN access to
> the Internet. Neither Enabled nor Disabled are checked, no IP numbers are
> entered and all schedule times are set to zero. When I finish  this email
> I'll explictly disable the filter function to see if some default is making
> mischief. 
>
>> If yes and you have that problem with multiple adapters then this is most
>> likely power related, especially since both systems are connected via ground
>> and can have all kind of electrical issues.
>
> I do see what looks like noise on the serial lines, but only after a spontaneous
> disconnect and only with FTDI adapters. When the serial connections are working
> nothing resembling noise is seen. 
>
>> In some cases it might be required to have an isolated adapter.
>
> A close look at the connection diagram will reveal a loop connecting all
> the FreeBSD systems via the serial port grounds. Breaking that loop by
> lifting ground on one serial cable ground made no difference. 
>
>> That said, beside all chips work well.
>> There are some bad boards however, which are unrelated to the chips themselves.
>> Also at least with the PL2303, CP2102 and some FTDI there are fake chips on
>> the market.
>> Other than that you might need specific features, some FTDI and CH340 can do
>> higher bps rates, which some rockchip based boards may need.
>> Also FTDI and CP2102 and a few others can have uniquie serial numbers, which
>> makes them easier to identify if you have multiple.
>> That's the reason why I like to use FT4232H based for my bench tests.
>> They can handle higher speeds and have serial numbers, plus they support
>> multiple uart at the same time.
>> I also have lots of CP2102, which I build myself and know those are technically
>> good.
>> 
>
> That's helpful information. It sounds like there's little preference between
> pl2303, ft232, ch340 and cp2102. 
>
> Thanks for writing!
>
> bob prohaska