To transform the Kunbus Revolution Pi into an industrial control unit, various digital I/O modules can be connected to the base module RevPi Core. The I/O modules come in three versions. All have the same 28-pin I/O connector at the front (connector with two rows of 14 pins each two suitable 14-pin socket connectors with spring clamp contacts for the connection of up to 1.5 mm² stranded hookup wires are supplied). The Kunbus RevPi DIO Module (standard version) features 14 digital inputs and 14 digital outputs. All versions have galvanic separation between PiBridge logic circuit and inputs resp. outputs (600 VRMS isolation voltage). The RevPi DIO version has additionally galvanic separation between inputs and outputs. All versions are protected against interference according to EN61131-2 requirements and may be operated between -40°C to 55°C ambient temperature with up to 80% rel. humidity. Overall cycle time is around 5 ms for a system having 1 DIO and 2 RevPi Gate modules or 10 ms for a system having 3 DIO and 2 RevPi Gate modules.
The DC inputs have a voltage threshold which for 24 V supply voltage is compliant to EN61131-2 Type 1 and Type 3 input definitions. Input current is clamped at a maximum of 2.4 mA. This norm is not defined for 12 V inputs therefore we cannot test for any compliance. But thresholds are reasonably reduced with supply voltage. If voltage supply drops under 9 V, an alarm is sent to RevPi Core. This can be used as indication of unreliable input values which are no longer compliant to norm for a 24 V digital input. There is an adjustable low-pass filtering to prevent input signal bouncing. This filter can only be applied to all inputs or none. The filter only propagates input values which are stable for at least 25 µs, 750µs or 3 ms (value is part of configuration). All inputs are protected against ESD, bursts and surges according to demands of EN61131-2.
Each output can be configured separately as high side switch with max. 500 mA current load or push-pull output with a maximum load of 100 mA. Independently from their output mode each single channel is protected against over current and is short circuit safe. A hardware watchdog circuit is monitoring the SPI data exchange between MPU and output circuit. If there is no SPI traffic, outputs are forced to 0 (safe state). Outputs are also forced to their safe state if output power supply drops low or the output circuit reached an over-temperature condition. Such error conditions as well as short circuit state of each channel is cyclically transmitted to RevPi Core. Each output can additionally be configured to detect open load conditions when in high side switch mode and send an alarm to RevPi Core. Just like the inputs all outputs are protected against ESD, bursts and surges according to demands of EN61131-2.