Digital input/output specifications

Terminals configurable for digital input and output (I/O) including status high/low, pulse width modulation, external interrupt, edge timing, switch closure pulse counting, high-frequency pulse counting, UART Universal Asynchronous Receiver/Transmitter for asynchronous serial communications., RS‑232 Recommended Standard 232. A loose standard defining how two computing devices can communicate with each other. The implementation of RS-232 in Campbell Scientific data loggers to computer communications is quite rigid, but transparent to most users. Features in the data logger that implement RS-232 communications with smart sensors are flexible., RS-422 Communications protocol similar to RS-485. Most RS-422 sensors will work with RS-485 protocol., RS‑485 Recommended Standard 485. A standard defining how two computing devices can communicate with each other., SDM Synchronous Device for Measurement. A processor-based peripheral device or sensor that communicates with the data logger via hardwire over a short distance using a protocol proprietary to Campbell Scientific., SDI‑12 Serial Data Interface at 1200 baud. Communications protocol for transferring data between the data logger and SDI-12 compatible smart sensors., I2C Inter-Integrated Circuit is a multi-controller, multi-peripheral, packet switched, single-ended, serial computer bus., and SPI Serial Peripheral Interface - a clocked synchronous interface, used for short distance communications, generally between embedded devices. function. Terminals are configurable in pairs for 5 V or 3.3 V logic for some functions.

NOTE:

Conflicts can occur when a control port pair is used for different instructions (TimerInput(), PulseCount(), SDI12Recorder(), WaitDigTrig()). For example, if C1 is used for SDI12Recorder(), C2 cannot be used for TimerInput(), PulseCount(), or WaitDigTrig().

Maximum Input Voltage: ±20 V

Logic Levels and Drive Current:

Terminal pair configuration	5 V source	3.3 V source
Logic low	≤ 1.5 V	≤ 0.8 V
Logic high	≥ 3.5 V	≥ 2.5 V
C1 - C4	10 mA @ 3.5V	10 mA @ 1.85V
U odd	20 mA @ 3.5V	20 mA @ 1.85V
U even	10 mA @ 3.5V	10 mA @ 1.85V

Switch closure input

Terminals: C1-C4, U1-U12

Resistance: Configurable in terminal pairs with 100 kΩ pull-up or pull-down

Maximum Input Frequency: 150 Hz

Minimum Switch Closed Time: 5 ms

Minimum Switch Open Time: 6 ms

Maximum Bounce Time: 1 ms open without being counted

Software Debounce Time: 3.3 ms

High-frequency input

Terminals: C1-C4, U1-U12

Resistance: Configurable in terminal pairs with 100 kΩ pull-up or pull-down

Typical Wave Form: 5 or 3.3 VDC square wave

Maximum Input Frequency: 1 MHz

Edge timing

Terminals: C1-C4, U1-U12

Maximum Input Frequency: ≤ 1 kHz

Resolution: 520 ns

Edge counting

Terminals: C1-C4, U1-U12

Maximum Input Frequency: ≤ 2.2 kHz

Quadrature input

Terminals: C1-C4 and U1-U12 can be configured as digital pairs to monitor the two sensing channels of an encoder.

Maximum Frequency: 2.5 kHz

Resolution: 31.25 µs or 32 kHz

Pulse-width modulation

Modulation Voltage: Logic high

Maximum Period: 128 seconds

Resolution:

0 to ≤ 5 ms: 1/12 MHz or 83.33 ns
> 5 to ≤ 300 ms: 187.62 kHz or 5.33 µs
> 300 ms: 1/32 kHz or 31.25 µs