[Soekris] serial port on 4501

[Henry Spencer]

On 16 Apr 2003, Rahul Kalaskar wrote:
> The problem seems to operation of serial port on net4501. The serial
> driver  (/proc/tty/drivers/serial ) says that the RTS and DTS lines on
> the serial port are on. But, on connecting a RS-232 line analyser, I
> find that none of the lines are on. In fact, I measured the voltages on
> the serial lines. None are carrying any voltages...

A possibly-relevant comment from Soeren in late November last year:

"The net45xx series manufactured until about 2 months ago had the RS232
transceiver configured in a auto power saving mode where it turned
itself off if there isn't any active inputs...
Older boards can be modified by cutting the thin trace from U5 (MAX3243)
pin 23 to the capacitor next to it, and instead connecting pin 23 to pin
22 with a solder bridge.
The updated boards are net4521 dated 020922, net4511 dated 020922 and
net4501 dated 020910."

                                                          Henry Spencer
                                                       henry at spsystems.net