[GTALUG] Actual ttyS0 MIA

[Alvin Starr]

On 5/7/20 10:52 AM, Stewart C. Russell via talk wrote:
> On my desktop (i7-4790K, 32 GB DDR3, Asus H97M-E) I've run out of 
> serial ports I can usefully access via USB serial adapters*. The 
> motherboard does have a real COM port on it, though, and just after I 
> built the system I added an adapter cable/bracket (one of these, IIRC: 
> https://www.canadacomputers.com/product_info.php?cPath=5_1336_1449&item_id=094057). 
> But it's never worked as a port, and I want to make it work.
>
> It's enabled in the BIOS and Linux (Ubuntu 19.10) finds it:
>
>     ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
>
> I'm a member of `dialout`, and the ports seem to check out:
>
>     $ ls -l /dev/ttyS0 /dev/ttyUSB0
>     crw-rw----  1 root dialout   4, 64 May  6 21:54 /dev/ttyS0
>     crw-rw----+ 1 root dialout 188,  0 May  3 07:50 /dev/ttyUSB0
>
> No data goes in or out. Curiously `stty -F /dev/ttyS0` hangs for a few 
> seconds, but that's the only odd thing I see.
>
> Hardware serial ports are kind of ancient history. Anyone remember 
> ancient magic to make 'em work? There's a chance that ASUS don't use 
> the standard serial pin header assignment: I'll trace that if necessary.
The headers and cables tended to be pretty standard.
Usually the headers have a pin missing  and the plug would have a hole 
filled but if not it would be easy to put the cable on backwards.

you should make sure you have hardware flow control disabled.

There are a number of programs for managing serial ports but I have had 
reasonably good luck with minicom.


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Alvin Starr                   ||   land:  (647)478-6285
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