4.5 Accessing Serial Commands from
Modbus or Analog Mode
1. Connect the USB cable to your PC and start the terminal application as instructed in
Connecting with a Computer (page 27).
2. Start a new terminal session using the default serial settings.
3. Keep the Enter key pressed down and connect the probe to the USB cable. When the
probe is powered on (connected to your PC with the USB cable), you must send
five
carriage returns (Enter key presses) within 0.7 seconds to force the probe to serial
command mode. The probe model information appears in the terminal application
when the mode has been succesfully changed, and Vaisala Industrial Protocol
commands are available for use.
4. To test the connection, enter for example the ? command. If the mode change failed,
close the terminal application, disconnect the probe from the USB cable, and repeat
step 2 and step 3.
5. To keep the serial mode in use (forced serial mode access is temporary and switches
o
at reset), select a serial output option (stop/run/poll) with the smode command.
Note that the probe always remains in analog mode when pin #5 is connected to pin
#3, and cannot be switched to digital output in this wiring option.
More Information
‣
Serial Interface Settings (page 27)
‣
Enabling Modbus Mode from Vaisala Industrial Protocol (page 30)
4.6
Enabling Modbus Mode from Vaisala
Industrial Protocol
If you need to switch from Vaisala Industrial Protocol to Modbus mode, you must
configure
the following settings:
• Serial line operating mode
• Modbus address
• Serial line settings (bit rate, parity, stop and data bits)
1. Connect the USB cable to your PC and start the terminal application as instructed in
Connecting with a Computer (page 27).
GMP252 User Guide M211897EN-D
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