Serial Port Problems

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This just isn't making any sense.  I'm using the Gigabyte EP43-U3DL board which has one serial port built in and appears as a header connector on the board itself.  I have a header to db9 adapter and have confirmed that is pin for pin correct end to end.

 

During unRaid boot, syslog shows:

 

Serial: 8250/16550 driver, 1 ports, IRQ sharing disabled

serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

00:07: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

 

which looks AOK to me, the port should be working on /dev/ttyS0, right?

 

The only comm program I could find for testing is minicom, which seems modem-centric but also appears to be able to talk to a port even if modem commands fail.  Set at 38400 bps or 2400 bps (for talking to an APC UPS port) there is no communication at all.

 

I made up a loopback db9 plug which connects pins 2&3 (recv and transmit data) together, pins 1&4 (RTS to CTS) together, and pins 7&8 (DCD to DTR) together which should echo anything I type on minicom back to the console, but it doesn't.  It's as if the hardware is there but there's no software driver (which I doubt).

 

Setting minicom to 2400 bps 8N1 it can't talk to the UPS either.  I've confirmed that another machine with a working serial port will talk to the UPS at 2400 bps no problem.

 

apcupsd doesn't see it either.

 

Is there anything else that needs to be done in Slackware (unRaid) to get this working?  From what I've read around the forum, it should 'just work'.

 

Is there a more basic comm program to use for testing?  Any other suggestions?

 

--Bill

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I picked up a supposedly 16550 compatible AT Native dual serial board today, but it turned out not to be an exact emulation.  Linux saw it as COM 1 and recognized the UART but was unable to initialize it.  Then in small print on the package, a statement about all Windows drivers included.  Well, a truly compatible board wouldn't need its own drivers.

 

This motherboard has a 16550 compatible UART as well, but apparently not quite compatible enough for the Slackware drivers.

 

I'm not really sure what else to try at this point.

 

--Bill