Carrier Detection in FreeBSD Post: 302821877

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Operating Systems BSD Carrier Detection in FreeBSD Post 302821877 by rstor on Saturday 15th of June 2013 11:00:58 PM

06-16-2013

Registered User

My question was that according to my understanding of the documentation found here:

(27.4.6.1. Checking Out the FreeBSD System)
27.4.�Dial-in Service

When FreeBSD sees no carrier, getty should not have completed its open on the communications port. According to the setup described in my opening post, getty was opening the communications port regardless of carrier when the system is brought up. However; once there is a carrier signal applied, then it behaves correctly to my understanding.

I have found out where my problem was. Here is what I did:

I took two DB9 Male-Female connectors and removed all pins except receive, transmit, and ground. I connected the two connectors to each end of my null modem cable. The end result is a null modem cable that will only use these three lines.

I installed FreeBSD on an actual machine with a serial port (instead of using FreeBSD on VM Virtual Box with a usb-serial dongle). I connected my modified null modem cable to the FreeBSD machine and the other end to a PC.

Executing ps -ax on the above FreeBSD machine resulted in the following:

Code:

749 ?? S 0:00.01 /usr/libexxec/getty std.300 ttyu0

This is the correct behaviour to my understanding.

Using the modified cable on the virtual FreeBSD machine connected to a PC and executing ps -ax resulted in the following:

Code:

683 u0 Ss+ 0:00.06 /usr/libexec/getty std.300 ttyu0

Conclusion:

On the virtual FreeBSD machine which had a usb serial dongle, getty opens the communication port on system startup which it should not do to my understanding. On a real system it performs as indicated in the documentation.

rstor

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LEARN ABOUT FREEBSD

uark

UARK(4) 						   BSD Kernel Interfaces Manual 						   UARK(4)

NAME

     uark -- Arkmicro Technologies ARK3116 based USB serial adapter

SYNOPSIS

     To compile this driver into the kernel, place the following lines in your kernel configuration file:

	   device usb
	   device ucom
	   device uark

     Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

	   uark_load="YES"

DESCRIPTION

     The uark driver supports Arkmicro Technologies ARK3116 based serial adapters.

HARDWARE

     The uark driver supports the following adapters:

     o	 HL USB-RS232
     o	 HugePine USB-UART
     o	 KQ-U8A Data Cable
     o	 Skymaster USB to RS232

SEE ALSO

     tty(4), ucom(4), usb(4)

HISTORY

     The uark device driver first appeared in OpenBSD 4.0.  The first FreeBSD release to include it was FreeBSD 7.0.

AUTHORS

     The uark driver was written by Jonathan Gray <jsg@openbsd.org>.

CAVEATS

     Setting hardware flow control is not currently supported.	It is not yet known how to ask the hardware to send a break.

     Arkmicro Technologies do not reply to requests of documentation for their products.

BSD
								 November 20, 2011							       BSD