General serial communications

The data logger supports two-way serial communications. These communications ports can be used with smart sensors that deliver measurement data through serial-data protocols, or with devices such as modems, that communicate using serial data protocols.

ClosedCRBasic Campbell Scientific's BASIC-like programming language that supports analog and digital measurements, data processing and analysis routines, hardware control, and many communications protocols. instructions for general serial communications include:

  • SerialOpen()
  • SerialClose()
  • SerialIn()
  • SerialInRecord()
  • SerialInBlock()
  • SerialInChk()
  • SerialOut()
  • SerialOutBlock()
  • SerialBrk()
  • SerialFlush()

See the CRBasic Editor help for detailed instruction information and program examples: https://help.campbellsci.com/crbasic/cr6/ .

To communicate over a serial port, it is important to be familiar with the protocol used by the device with which you will be communicating. Refer to the manual of the sensor or device to find its protocol and then select the appropriate options for each CRBasic parameter. See the application note Interfacing Serial Sensors with Campbell Scientific Dataloggers for more programming details and examples.

Configure C or U terminals as serial ports using ClosedDevice Configuration Utility Software tool used to set up data loggers and peripherals, and to configure PakBus settings before those devices are deployed in the field and/or added to networks. Also called DevConfig. or by using the SerialOpen() CRBasic instruction. C and U terminals are configured in pairs for TTL and LVTTL communications, and C terminals are configured in pairs for RS-232 or half-duplex RS-422 and RS-485. All four C terminals are required for full-duplex RS-422.


RS-232 single-ended full-duplex communications


RS-485/RS-422 differential-pair full-duplex communications


RS-485 differential-pair half-duplex communications

Serial communications summary

 

RS-232

RS-485

RS-422

TTL

LVTTL

TTL-INV

LVTTL-INV

Communications

Point-to-point

Multi-drop

Single ended

Multi-drop

Point-to-point

Point-to-point

Point-to-point

Point-to-point

Maximum number of devices

1 Transmitter

1 Receiver

32 Transmitters

32 Receivers

1 Transmitter

10 Receivers

1 Tx

1 Rx

1 Tx

1 Rx

1 Tx

1 Rx

1 Tx

1 Rx

Mode type

Full duplex

Full duplex

Half duplex

Full duplex

Half duplex

Full duplex

Full duplex

Full duplex

Full duplex

Reference

Single wire

Tx ref to GND

Differential pair

TxB+ referenced to TxA–

Single wire

Tx referenced to GND

Voltage range

–25 V to 25 V

–5 V to 5 V

–6 V to 6 V

0 V to 5 V

0 V to 3.3 V

0 V to 5 V

0 V to 3.3 V

Idle voltage

–25 V to
–3 V

–0.2 V to 5 V

–0.2 V to 6 V

5 V

3.3 V

0 V

0 V