Campbell-scientific CR800 and CR850 Measurement and Control Systems Instrukcja Użytkownika Pobierz pdf (Strona 209)

100

101

Section 7. Installation

209

1. Open a serial port (SerialOpen() command) to configure it for

communications.

• Parameters are set according to the requirements of the communications link

and the serial device.

• Example:

SerialOpen(Com1,9600,0,0,10000)

• Designate the correct port in CRBasic.

• Correctly wire the device to the CR800.

• Match the port's baud rate to the baud rate of the device in CRBasic.

• Use a fixed baud rate (rather than auto baud) when possible.

2. Build the output string.

• Example:

SerialOutString = "*" & "27.435" & "," & "56.789" & "#"

• Tip — Concatenate (add) strings together using & instead of +.

• Tip — CHR() instruction is used to insert ASCII / ANSI characters into a

string.

3. Output string via the serial port (SerialOut() or SerialOutBlock() command).

• Example:

SerialOut(Com1,SerialOutString,"",0,100)

• Declare the output string variable large enough to hold the entire

concatenation.

• Example:

Public SerialOutString As String * 100

• SerialOut() and SerialOutBlock() output the same data, except that

SerialOutBlock() transmits null values while SerialOut() strings are

terminated by a null value.

7.8.8.5.4 Translating Bytes

One or more of three principle data formats may end up in the SerialInString()

variable (see examples in Serial Input Programming Basics

(p. 207) ). Data may be

combinations or variations of all of these. The manufacturer of the instrument

must provide the rules by which data are to be decoded.

• Alpha-numeric: Each digit represents its own alpha-numeric value. For

example, R = the letter R, and 2 = decimal 2. This is the easiest protocol to

translate since the literal translation is what is received from the transmitting

instrument. Normally, the CRBasic program receiving the transmission will

be written to parse (split) the string up and place the values in CR800

variables.

Example (humidity, temperature, and pressure sensor):

SerialInString = "RH= 60.5 %RH T= 23.7 °C Tdf= 15.6 °C Td=

15.6 °C a= 13.0 g/m3 x= 11.1 g/kg Tw= 18.5 °C H2O=

1 2 ... 204 205 206 207 208 209 210 211 212 213 214 ... 565 566

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