90088262 MCS130B
CORNERSTONE 130B MONOCHROMATORS
46
15.2
TROUBLESHOOTING RS-232
One of the most common problems when first connecting a PC to an RS-232 device is that the
cable may swap the signals. The cable should be the straight-through type, and i
f you aren’t sure
that it is, there are a couple of things you can try.
The simplest is to connect an ohmmeter between pin 3 on the PC end of the cable and pin 3 on
the device end. There should be no resistance between them. The same goes for pin 2. And just
to be sure, also check pin 5: sometimes there is a break in the cable.
The nomenclature for RS-232 has suffered a great deal of re-
naming and the “standard” has
become non-standard, but most PCs now transmit signals on pin 3 of their DB-9 connector, and
receive signals from pin 2. The Transmit signal (Tx) is held at roughly -9V (the actual voltage
depends on the PC) when not transmitting, and the Receive signal (Rx) is floating. So another
troubleshooting method is to first connect one end of the cable to the PC, and connect a
voltmeter between pins 3 and 5 on the other end. You should see some negative voltage
between pin 3 and pin 5, and close to 0V between pin 2 and pin 5.
The CS130B receives on pin 3 (device Rx) and transmits on pin 2 (device Tx). The PC transmits
to the CS130B
’s Receive pin, and receives from the CS130B’s Transmit pin.
The CS130B implements two RS232 communications modes that may be useful when problems
arise. They
are “echo” and “handshake”. See the following sections for more information about
them.
One of the most useful tools is called a “sniffer”. It monitors and displays traffic on the transmit
and receive lines so that you can verify that the PC is sending what you want it to, and examine
what the device is sending. The EZ-Tap from Stratus Engineering is a good example.
The “activity” LED on the CS130B panel blinks rapidly when the CS130B receives a command on
the RS232 or USB. This is the small light in the lower right corner of the panel. It normally blinks
at a 1 Hz rate to show that the unit is powered up and ready. It blinks quickly when the grating or
filter wheel are moving, or when a command is received on the USB or RS232 port. Make sure it
blinks quickly a couple of times when you send a command.
DB-9 connector at end of cable, other end connected to PC.
6
5
1
9
V from pin 3 (PC Tx) to pin 5 (gnd) ~ -9V
Содержание Cornerstone 130B
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Страница 32: ...90088262 MCS130B CORNERSTONE 130B MONOCHROMATORS 32 Figure 23 Model 74010 Filter Wheel...
Страница 42: ...90088262 MCS130B CORNERSTONE 130B MONOCHROMATORS 42 14 13BDIMENSIONS Figure 30 Cornerstone 130B Dimensions...
Страница 44: ...90088262 MCS130B CORNERSTONE 130B MONOCHROMATORS 44 Figure 33 Model 74006 Mounting Plate...
