Campbell CR6 Series, Руководство оператора

Страница: 366 / 690

Section 7. Installation
366
protocol to translate since the encode and translation are identical.
Normally, the CR6 is programmed to parse (split) the string and place
values in variables.
Example string from 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= 17889
ppmV pw=17.81 hPa pws 29.43 hPa h= 52.3 kJ/kg dT= 8.1 °C"
•
Hex Pairs
— Bytes are translated to hex pairs, consisting of digits 0 to 9
and letters a to f. Each pair describes a hexadecimal ASCII / ANSI code.
Some codes translate to alpha-numeric values, others to symbols or
non-printable control characters.
Example sting from temperature sensor:
SerialInString = "23 30 31 38 34 0D"
which translates to
#01 84 cr
•
Binary — Bytes are processed on a bit-by-bit basis. Character 0 (Null,
&b00) is a valid part of binary data streams. However, the CR6 uses
Null terminated strings, so anytime a Null is received, a string is
terminated. The termination is usually premature when reading binary
data. To remedy this problem, use SerialInBlock() or
SerialInRecord()
when reading binary data. The input string variable
must be an array set As Long data type, for example:
Dim SerialInString As Long
7.7.18.5.5 Serial I/O Memory Considerations
Several points regarding memory should be considered when receiving and
processing serial data.
• Serial buffer: The serial port buffer, which is declared in SerialOpen() ,
must be large enough to hold all data a device will send. The buffer
holds the data for subsequent transfer to variables. Allocate extra
memory to the buffer when needed, but recognize that memory added to
the buffer reduces final-data memory
(p. 583).
Note Concerning SerialInRecord() running in pipeline mode with
NBytes (number of bytes) parameter = 0:
For the digital measurement sequence to know how much room to allocate
in Scan()
buffers
(default of 3), SerialInRecord() allocates the buffer size
specified by
SerialOpen()
(default 10,000, an overkill), or default 3 •
10,000 = 30 kB of buffer space. So, while making sure enough bytes are
allocated in SerialOpen() (the number of bytes per record •
((records/Scan)+1) + at least one extra byte), there is reason not to make
the buffer size too large. (Note that if the NumberOfBytes parameter is