Campbell CR800 Series User Manual

Section 7. Installation
289
7.7.17.5.4 Serial I/O 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. 286) ). Data may be
combinations or variations of these. The instrument manufacturer must provide
the rules for decoding the data
• Alpha-numeric — Each digit represents an alpha-numeric value. For
example, R = the letter R, and 2 = decimal 2. This is the easiest
protocol to translate since the encode and translation are identical.
Normally, the CR800 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 CR800 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
7.7.17.5.5 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. 499).

Campbell CR800 Series Specifications

General

Brand	Campbell
Model	CR800 Series
Category	Data Loggers
Language	English