Hardware flow control problem (banging head against brick wall)

Hardware flow control problem (banging head against brick wall)

Post by malcolm gambl » Fri, 08 Jun 2001 19:30:39

Hope someone can put me out of my misery.

I am writing a program to try and use hwflow (CTS/RTS) on linux
(kernel 2.4.3)
When CTS drops linux still sends data. I am using these port settings,
and opening the port with O_NONBLOCK, when I get a connect message I
turn O_NONBLOCK off. I always select() the port before
sending/receiving data. I have tried using tcdrain(), sending a byte
at a time and using O_SYNC with the open.
I also seem to get the same problem with SCO too.
If I set the port to 115200, rather than 38400 it makes no difference
at all.
Yet if I turn HWflow off at 115200 the serial port gets garbage, so it
to some extent hwflow is working, but not if the modem at the other
end causes the CTS to drop. All cabling is correct and has been

I have 2 USR 3com 56k faxmodem (external) all uarts are ok
modem settings are OK I think and are the same at both ends.

Modem Settings


Port Settings

#define LFLAGS_SET 0
#define C_FLAGS_BI_HWFLOW_SET (CRTSCTS)  /*     For linux       */
/*#define C_FLAGS_BI_HWFLOW_SET ( RTSFLOW|CTSFLOW ) *//*        For SCO         */
(*port_attributes).c_cflag = 0 ;
(*port_attributes).c_cflag |= CFLAGS_SET ;
(*port_attributes).c_cflag |= C_FLAGS_BI_HWFLOW_SET ;
(*port_attributes).c_iflag = 0 ;
(*port_attributes).c_iflag |= IFLAGS_SET ;
(*port_attributes).c_oflag = 0 ;
(*port_attributes).c_lflag = 0 ;


1. I am beating my head against a Brick wall - OpenSSH, OpenSSL and GNU software

I have a vanilla system. To that I have added the bonus software.

I have downloaded OpenSSH, and OpenSSL from Sunfreeware, tried setting up
ssh and it complains that it cannot find libgcc-*

Do a find / -print | grep libgcc and low and behold no file found.  Download
gcc-3.0.1 waste of time, it complained that ln -s was overwriting an
existing file, tried adding -f, and it still complains - dumped it.

Download gcc-3.0, it compiles fine, complain about ld, but that was fixed by
getting binutils, but now after all that effort OpenSSL complains:
ld.so.1: ssh: fatal: relocation error: file
6: symbol main: referenced symbol not found

I am now going to try with 2.95.3 to see if I can at least get it working.
But any ideas such that I do not stuff up again.

I think last time I did it in the following order:
gcc-2.95 > Compile gcc-2.95.3 > compile binutil > Install OpenSSL > Install
OpenSSH > Ran ssh > compiled gcc-3.0 in 32bit
Wayne Jackson


2. Limiting SSL to one virtual host

3. Head Hurts from Banging Against Wall

4. What would be the advantage of AIX running NT vs. Novell 5 ?

5. Tape backup utilities: Banging my head agains the wall.

6. using find cmd to locate files by date

7. *bang* *bang* - the sound of my head hitting the monitor


9. UUCP 1.05 hardware flow control problem!

10. dip hardware flow control

11. Hardware Flow Control & Xenix

12. Banging my head on a NON FS problem

13. hardware control flow RTS/CTS with LINUX