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The EXP-IO expansion board is a mixed input/output module that features:

  • Relay: The board features 4 Solid state relays Normally open connection rated at 36Vdc, This enables developers to control actuators easily using Software libraries with Zerynth SDK.
  • Opto-isolated digital inputs: 2 channels of opto-isolated digital inputs are available on the board.
  • 2 Analog Channels channels: Connect your sensor easily and read the data from the sensors over the 2 industrial-compatible channels on the board. The channels support voltage-based ( ±10V), current-based (±20mA) or resistive sensors (calibrated for 11 Kohm for best precision).

Device Summary

  • 4x Solid State Relays NO. Uses the TLP172A, Rated at 36Vdc.
  • 2 opto-isolated digital inputs Uses ISO1212DBQR IC rated for 36Vdc.
  • 2 Analog Channels channels Each channel can be configured as
    • 4-20 mA Current channel (full input range ±20mA)
    • 0-10V Voltage channel (full input range ±10V)
    • Resistive Sensor Channel.Internal bias is designed for NTC thermistor probes rated 10kΩ @ 25°C (with B=3435), but other probes may also be used depending on the temperature range to be measured.
    • Current Clamp channel based on voltage or current signal( within channel Voltage and current ratings).

Resources and Documents

Software Library

For more information on the EXP-IO Library as software Library, features, functions and examples Please check this Link

Pin Mapping

Rotart and Standard switches

For information on the switches and other hardware details, Please refer to the User manual of the board


Power to the EXP-IO is supplied directly by the ZM1-DB.


The modular expansion system uses the Z-Bus. The Z-Bus is an efficient, powerful standard for connecting and prototyping different sensors and devices. The Z-Bus is using the CN1 pin header (20x2) exposing the following:

  • 16 GPIO pins.
  • 4 interrupt pins.
  • 2 USART/UART instances with full support (TX,RX,RTS,CTS)
  • I2C, SPI support.
  • 5V, 3.3 V output pins.
  • Enable pin for controlling the power to attached expansion boards.


The development boards support up to 3 attached expansion boards.

Expansion boards vary in features and functionality. Currently, Zerynth offers expansion boards for :

  • EXP-AIN: Expansion board with 8 Industrial analog input channels
  • EXP-CONNECT: GSM-NB-IoT and GPS enabled expansion module.
  • EXP-IO: Industrial input/output board with 4 solid-state relays, 2 analog channels (4-20mA/0-10V/NTC/current clamp) channels, 2 opto-isolated digital inputs
  • EXP-RELAY: Relay board with 6 Electromechanical power relays rated 6A 250VAC.
  • EXP-SER: Serial Communication board with : CAN, RS232 and RS485 interfaces.
  • EXP-PROTO: Prototyping board for connecting and testing different types of sensors and devices.