GPIO interfacing

Sensoray offers a number of products that have general purpose digital I/O (GPIO) interfaces. When interfacing a GPIO to external circuitry it is important to follow some basic design rules to ensure proper operation and avoid damage to the GPIO and external circuit:

• Input range - When the GPIO is acting as an input or wired-OR, make sure the external signal source will never exceed the GPIO's input voltage range. In the case of TTL/CMOS compatible GPIOs (e.g., models 826 and 2410), the input range is typically 0 to +5 V. Some products support wider voltage ranges; for example, the model 2610 input voltage range is 0 to +24 V.

• Common ground - If the GPIO is not isolated, the external circuit and GPIO interface must share a common power supply return. For example, in the case of a model 2410, the 2410's power supply return (i.e., negative power supply input) must be connected to the external circuitry's power supply return.

• Edge rate - Strive for fast signal edge rates when a GPIO is driven by an external signal source. Slow rise and fall times can cause sampling errors and, in extreme cases, damage to GPIO line receivers.