Lin Zhe Min (ljm@ljm.wownet.net)
Sun, 7 Dec 1997 14:04:41 +0800 (CST)
Dear Sir,
I met a problem when I was trying to make a cable line to connect my
Phoenixtec UPS 500VA and computer which is running Linux 2.0.29 on a
Pentium MMX-166 on the Asus P55XT2P4 mainboard. Powerd 2.0 is used.
The 9-pin signal port of my UPS is designed...
______
1 - GND 2 - BACKUP 3 - BACKUP 4 - COMMON (to 2,3,5)
5 - BATTERY 6 - SHUTDOWN 7 - NC 8 - COMMON (to 6)
9 - NC
When the power is failed, relais between BACKUP(2) and COMMON (4)
is closed, with approx. 9K Ohm in between.
According to UPS-Howto, I tried to make a simplest line to make a
connection: ( 9-pin RS-232 on /dev/cua0 )
RS-232 UPS
1 DCD ----+------------------- 2 BACKUP
|
[R] (10K Ohm)
|
4 DTR ----+
|
5 SG ------------------------ 4 COMMON
|
6 DSR ----+
However, according to my measure, I found one thing bizzare.
I grounded my multimeter to ground-line of a local electric co.,
and test each pin on my RS-232, reported:
1 DCD (0.0V) 2 RD (0.0V) 3 TD (0.0V)
4 DTR (-11.25V) 5 SG (0.0V) 6 DSR (0.0V)
7 RTS (0.0V) 8 CTS (+11.25V) 9 RI (0.0V)
(How come is DTR measured -11.25V ? ....)
And when I attached the cable, every pin is measured:
1 DCD (0.0V) 2 RD (0.0V) 3 TD (0.0V)
4 DTR (0.0V) 5 SG (0.0V) 6 DSR (0.0V)
7 RTS (0.0V) 8 CTS (+11.25V) 9 RI (0.0V)
(DTR is connected to DSR, and via a 10K Ohm resistor to DCD, so I
supposed -11.25V is flowed to DSR.)
This is anormal comparing to the original design. DCD is not high,
because electric flows (if any) from DTR to DCD is under 0, and caused
powerd detected a power failure (DCD low).
Briefly speaking, I have some questions:
1) How come DTR is measured -11.25V but not +11.25V ?
2) Even when the relais is closed, electric flows through DTR -> resistor
-> BACKUP -> COMMON -> SG with a 19K Ohm resist. How come, under
this situation, electric should flow from DTR to SG rather than
from DTR to DCD ? Why not make the connection like the following chart:
RS-232 UPS
1 DCD ----+
|
[R] (10K Ohm)
|
4 DTR ----+------------------- 2 BACKUP
|
5 SG ------------------------ 4 COMMON
|
6 DSR ----+
for resist value DTR -> BACKUP -> COMMON -> SG is only 9K Ohm.
Thanks for helping me.
73,
Lin Zhe Min.
..e'osai ko sarji la lojban. ==> 請支持邏輯語言。
..co'o mi'e lindjy,min. ==> 再見，我是林哲民。
-- To unsubscribe, send mail to: linux-parport-request@torque.net --
-- with the single word "unsubscribe" in the body of the message. --
This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:17:10 EST