Campbell Scientific CR10X Measurement and Control System - Manual (Page 233)

B-1
APPENDIX B. CR10X CONTROL PORT SERIAL I/O INSTRUCTION 15
B.1 SPECIFICATIONS
FUNCTION
Send/receive full duplex serial data through the
CR10X control ports.
NOTE: If the received data is numeric
values, Instruction 15 converts a maximum
of seven digits in a row. Leading zeros will
be counted as part of the seven digits; e.g.,
0000010.1223 will be read as 10.
INPUT
Applying Filters
Received data can also have simple ASCII
filters applied to locate the beginning of the
actual data set. Multiple filters can be applied if
the data are imbedded in a long string.
Applying filters can be especially useful when
reading data from serial sensors such as Global
Positioning Receivers (GPS).
Data sent by the sensor can be ASCII data
values, hexadecimal pairs in ASCII
representation, or decimal encoded binary bytes
(Section B3, Parameter 2).
OUTPUT
Output can be a preamble set of commands to
the sensor or data from the CR10X's input
locations (Section B3, Parameter 6).
BAUD RATES
1200 baud
300 baud
HANDSHAKE CONTROL LINES
REQUEST TO SEND or DATA TERMINAL
READY (RTS/DTR)
The CR10X signals the sensor that it is ready to
send or receive data. This line is always
asserted at the start of the instruction. If no
output is specified then the line acts like DTR
and remains asserted until all input is received.
If output is specified, the line acts like RTS,
asserted during output, not asserted while
receiving (Section B3, Parameter 4).
CLEAR-TO-SEND (CTS)
The sensor signals the CR10X that it is ready to
receive the preamble or data (Section B3,
Parameters 3 and 9).
LOGIC LEVELS
RS-232 - Logical 1 is low voltage. RTS/DTR
asserted is high voltage.
TTL - Logical 1 is high voltage. RTS/DTR
asserted is low voltage.
PARITY AND STOP BITS
RECEIVE
- ASCII and Hexadecimal Pairs in ASCII
Representation:
1 start bit, 8 data bits, no parity,
1 stop bit 8th bit ignored
- Binary to decimal equivalent:
1 start bit, 8 data bits, no parity,
1 stop bit
TRANSMIT
1 start bit, 8 data bits, no parity, 1 stop bit
B.2 SELECTED OPERATING DETAILS
Standard RS-232 logic levels range from 3 to 25
volts and -3 to -25 volts. The maximum and
minimum input to CR10X control ports is 5 and
0 volts, respectively.
Inputs exceeding these
limits may damage the CR10X . Figure B1
gives a circuit which may be used to limit
voltage levels to 0 to 5 volts. Each input (data
and handshake) that is out of the 0 to 5 volt
range requires one of these circuits, or
equivalent.