regoli@silver.bacs.indiana.edu (michael regoli) (10/25/88)
]:[
would some kind soul figure out why this cable situation doesn't work?
i'm trying to convert a DB-25 to a DB-9 interface.
i have a diablo 1640 printer with a rs232 serial interface. the cable is
hard-wired directly into the back of the printer, so all i'm working
with is the male DB-25 coming out. it breaks out as follows:
PIN# COLOR ASSUMED FUNCTION*
---- ----- ----------------------------
1 green protective ground (GND?)
2 red transmit data (TD)
3 orange received data (RD)
4 yellow request to send (RTS)
5 brown clear to send (CTS)
6 blue data set ready (DSR)
7 purple signal ground (GND?)
8 white data carrier detect (DCD)
20 black data terminal ready (DTR)
(*assuming the diablo cable is consistent with rs232 circuits--which it
should be, since the printer works with any 25-pin PC serial port.)
what i've done is connected the following pins:
DB-25 -------------> DB-9
----- ----
1 (prot gnd) ?
2 (TD) 3
3 (RD) 2
4 (RTS) 7
5 (CTS) 8
6 (DSR) 6
7 (sig gnd) 5
8 (DCD) 1
20 (DTR) 4
what have i done wrong? i suppose i've have the wrong pin-outs for the
9-pin serial port. (and yes, i've configured the port with the DOS MODE
command, too.) the computer is a true-blue IBM-AT (circa 1984).
thanks for your help!
--
|
| michael regoli
| ...rutgers!iuvax!silver!regoli
| regoli@silver.bacs.indiana.edu
| regoli@iubacs.BITNET
|cdold@starfish.Convergent.COM (Clarence Dold) (10/26/88)
In article <2521@silver.bacs.indiana.edu>, regoli@silver.bacs.indiana.edu (michael regoli) writes: > would some kind soul figure out why this cable situation doesn't work? > i'm trying to convert a DB-25 to a DB-9 interface. > [...] > what i've done is connected the following pins: > > DB-25 -------------> DB-9 > ----- ---- > 1 (prot gnd) ? > 2 (TD) 3 > 3 (RD) 2 > 4 (RTS) 7 > 5 (CTS) 8 > 6 (DSR) 6 > 7 (sig gnd) 5 > 8 (DCD) 1 > 20 (DTR) 4 > [...] The pinout you have is correct for an adpater from the old cable to the new 9pin port. You can verify which pins are being driven by the printer, which are expected to be received, and which are empty with a DVM (high impedance voltmeter). If pin 2 is really transmit data, measuring from pin 2, using pin 7 as reference should should -8V when idle. Other driven signals will show either +8v or -8V. This voltage might be different on different systems, but it should be a strong positive or negative. Pins attached to receivers will should some slight voltage, probably around 0.5v on pin 3. Pins that are unused should show 0V. The only catch to this DVM trick is that some systems will send unused pins to ground or +5 through a pullup or pulldown resistor. I recall that pin 6, DSR had to be high on a Diablo, before it would accept data. If this is pulled high inside the printer, then driven low by a PC signal, it could be that eliminating a few pins from your adapter will make it work. Try just pins 2 and 7 to start, to see if you can get any data through. -- --- Clarence A Dold - cdold@starfish.Convergent.COM (408) 435-5274 ...pyramid!ctnews!professo!dold MailStop 09-031 P.O.Box 6685, San Jose, CA 95150-6685