Apex Digital PC - Serial Communication; Modbus RTU Communication; Establishing Communication; Communication Programs

20 Serial Communication
Serial Communication
Connecting your device to a computer allows you to log the data that it generates. The pressure controller communicates
digitally through its communications connector and cable using a real or virtual  port on your computer. This section
of the manual shows you how to operate the pressure controller using ASCII commands.
Modbus RTU Communication
For details on Modbus commands, contact support (page 16).
Establishing Communication
After connecting your pressure controller using a communications cable, you will need to establish serial communications
through a real or virtual  port on your computer or programmable logic computer (PLC).
• If the device is connected to a serial port, note its  port number. This can be found in Windows® Device Manager.
• If you have used a USB cable to connect your device to your computer, then in most cases it will recognize your USB
as a virtual  port. If it does not, contact support (page 16).
The controller will be configured with the following settings:
•
Baud: 19200 (by default; others can be used if the computer, its software and the controller are all set to the same rate)
• Data bits: 8
• Parity: none
• Stop bits: 1
• Flow control: none
Communication Programs
Although the device will communicate with any compatible terminal program over RS-232, PuTTy is a common option A
USB port or  port will not supply enough power to your device to function. Please use another power source.
Configuring PuTTy
1. Download PuTTY from putty.org and run the installer.
2. Open PuTTY; it will start on the Configuration screen.
3.
Click on the Terminal category. The changes we
make here will cause PuTTY to act like a normal serial
terminal, such that pressing enter will move the cursor
to the next line and both what you type and what gets
returned stay on the screen:
• Check the box that says “Implicit LF in every CR.”
•
Select the “Force on” radio button in the “Local echo”
section.
4. Click Connection, and then the Serial subcategory.
• Set the Speed (baud) to 19200.
• Set the Data bits to 8.
• Set the Stop bits to 1
•
Ensure “None” is selected for both Parity and Flow
control.
5. Click on the Session category.
•
Select the “Serial” radio button under “Connection
type”.
• Check that the  port and baud rate (Speed) are
correct.
6.
Save your settings so they can be recalled again later.
✓
Note: In the following examples,  indicates an ASCII carriage return (decimal 13, hexadecimal D). For many devices,
this is the same as hitting the Enter key. Serial commands are not case-sensitive.
Polling Mode
Your controller is shipped in polling mode with a unit ID of A, unless requested otherwise. Each poll returns one line of
data every time you request it. To poll, simply enter its unit ID.
Poll the device: [unit ID]

Example: a (polls unit A)