[Soekris] help! modem locks up net4801

[George McCollister]

I had similar problems with the serial ports locking up the 4801. I'm 
running FreeBSD 5.3. I found that removing DCD, DSR, DTR, RIN, CTS from 
my cables fixed my problems on both serial ports (I have short ribbon 
cables running to a custom PCB which provides surge protection for all 
of the RS232 lines). I'm guessing the issue is with one of the input 
lines (DSR, CTS, RIN).

I don't think grounding is an issue for numerous reasons. I'm using a 
grounded custom wide range AC/DC power supply. Also have ground running 
from the power terminal to the case with a 14 AWG wire. All PCBs 
including the power supply, 4801, and RS232/Ethernet surge suppression 
are screwed to steel PEMs which are punched into the aluminum during 
manufacturing. The shield from the RS232 cable makes contact to chassis 
ground via the surge protection board.

I've been meaning to get to the bottom of this problem, but since we 
aren't planning to use DCD, DSR, DTR, RIN or CTS it hasn't been a priority.

I think I've seen this problem prior to the OS even loading. If you're 
experiencing these problems a good way to test this would be to go into 
the COM bios using the 1st port then connect the problematic cable to 
the second port. Its been several months, but I believe I tested this 
and even in the combios I was able to hard lock the 4801. Like I said 
after removing DCD, DSR, DTR, RIN, CTS I have experienced no problems!

Regards,
George McCollister
Senior Programmer
NovaTech LLC

Michael Smith wrote:

>Hi David,
>
>Does it work if you have the modem plugged in and turned on at boot and 
>don't power cycle it?
>
>A couple of years ago I found I could pretty reliably lock up a net4801's 
>serial console by connecting a cable to it after power-up. It is probably 
>long fixed by now, but I haven't tried in a while - I just learned not to 
>do that, simple enough :)
>
>Mike
>
>On Wed, 21 Sep 2005, David Evensky wrote:
>
>  
>
>>I have a debian sid based mini linux distro (2.6.13 kernel.org) on a
>>microdrive. It runs beautifully with a null modem serial cable in the
>>built in serial port. If I use a usb serial adapter, I can use a null
>>modem cable, or a real modem, and that also works. However, if I plug
>>a real modem into the built in serial port, the net4801 locks up tight
>>and must be reset.
>>    
>>
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>  
>



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