INFICON Q-pod Thin Film Deposition Monitor - Manual (Page 23)

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Q-pod Operating Manual
Chapter 3
Communications
3.1 Introduction
The Q-pod communicates via a USB (or USB2) port and a simple ASCII command
set. An ActiveX DLL (Qpod.DLL) provides functions to set parameters, take
readings, and handle USB communications.
3.2 ASCII Command Set
The commands below assume you can open the proper USB port for
communications. The section on Qpod.DLL provides the tools needed to
communicate with the Q-pod without knowledge of USB functions.
A Q-pod command consists of an exclamation character (&H21), then the
command as detailed below, and terminated with a Carriage Return (&H13) and
Line Feed (&H10). The response has the same format, that is !<response>CrLf.
@ Get version
Returns: Qpod VX.XX
A# Get Frequency and Set Status LED
Returns frequency counts. The B & C commands (see below) must be used to
set the measurement period before using this command. The response is gate
counts, which are converted crystal frequency using:
Freq = 200 MHz * GatePeriod / Response
A response of –1 indicates that a new reading is not available.
The value sent with this command activates the Status LED. Send A1 to turn
on the LED (crystal good), or A0 to cause the LED to flash at the measurement
rate (crystal fail).
B# Set Gate Period
Sets the longest measurement period, determined by the lowest valid crystal
frequency. If the desired measurement period is 0.25 seconds, and the
minimum crystal frequency is 5.0MHz, then the command is: B1250000 (0.25
x 5MHz).
C# Set Measurement Period
The value sent is the period in seconds times the reference oscillator frequency,
50MHz. If the desired measurement period is 0.25 seconds, then the command
is: C12500000 (0.25 x 50MHz)