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ADP120 / ADP102 Isolated DIO module

The OnLogic ADP120/ADP102 provides isolated digital inputs and outputs for safe external signal control. The adapter USB interface and wide input voltage range offer enhanced versatility. The onboard ARM processor allows for fast, reliable operation independent of host system.

Systems from 2021 or older may use the ADP102, instead of the ADP120. These are functionally identical except for the hardware ID of the device. If you’re not sure which device you have, you can check for the following hardware IDs to confirm:

  • 1FC9:0094 = ADP120
  • 15A2:0300 = ADP102

Connector Type

Due to the wide variety of potential applications, OnLogic does not supply a mating connector. Below is an example list of connectors compatible with this module.




  • Isolated Digital Input/Output
  • Four Inputs, 0-16V (2.5V HIGH), dry contact 
  • Four Outputs, 50mA, open collector 
  • Keyed 2.54mm connector 
  • IO Isolation to 3750 Volts (​*Rated, not tested​) 
  • Simple-to-program USB-serial interface 
  • Onboard ARM Cortex-M0 processor
  • Latches and 32-bit counters for inputs 

Connections & Wiring 

DIO Header (externally facing)

The header is 2×8 pins, 2.54mm pitch, with shroud and key

For mating connector, use Wurth Electronics 61201623021 or similar.

USB J1 (Left) MISC J2 (Right)

Sample Input Circuit

Digital inputs are triggered by the flow of a small amount (1-2mA) of current through DI. Current is limited, and  correct polarity is ensured by the ADP/120/ADP102’s built-in protection circuit. A request for DI state will report active  when the voltage at DI exceeds 2.5 V. 

Sample Output Circuit 

Digital outputs switch a circuit in series after the device they control (represented by LOAD). Each output is  rated for 50mA. If more than 50mA are required, DO may be used to trigger a relay driving LOAD instead. 

Application Interface 

The ADP120/ADP102 provides a standard USB-CDC (USB-serial) interface. To determine the COM port number, check device manager or equivalent for the COM device. A developer may employ any  serial-compatible software library in order to communicate with the ADP120/ADP102.  Available commands are outlined below. After the execution of any command, a response is returned by the  ADP120/ADP102 containing any requested data. For commands that do not return a value, a success/failure code is  returned instead. 

Command Structure 

Each command is comprised of a start character, length (not including the start character), 1-byte pin address,  2-byte command ID, and (optional) data.  For example, to set the state of digital output 3 to ‘ON’, the command packet is: 

StartLengthAddressCommand HighCommand  Low Data
0x24 0x05 0x030x010x020xFF
Command High and Command Low can also be read as 0x0102 (in this example)

Digital Output Commands 

Get State  0x0101AddressGet the IO pin input state. Returns the status of output pins as well.
Get Latch State0x0102AddressGet the input pin latch bit state.
Get Count0x0103AddressGet the input pin counter value. This counter is  incremented at every low-to-high or high-to-low  state change, depending on configuration.
Clear Count 0x0104AddressReturn the input counter value, then reset it to  zero. 
Set State0x0108Address, StateSet an output pin to the specified state. 0x00  species LOW, all others evaluate to HIGH. 
Toggle State 0x0109AddressToggle an output pin to the opposite state.
Get Model Number0x0001NoneReturn the device model number.
Get Configuration0x0004AddressReturn the configuration of the specified pin. 
Set Configuration0x0005Address,  Configuration Set the configuration of the specified pin.  Available configuration settings are described in  the section below. Unless this is followed by  “Save Configuration” this is not preserved across  reboots. 
Save Configuration0x00060x00Save all pin configurations as “boot” settings.  0x00 must be provided in the data field. 

Response Structure 

 After executing each command, the ADP120/ADP102 issues a response containing data the command generated (if any)  and a success code.   The first two bytes of a response packet are the incoming command code that generated the response OR’d  with 0x8000, followed by the pin number requested and any relevant data. The packet is completed by the  same carriage return delimiter as the command packet. 

 For example, a response to the ‘Get input status’ command looks like this: 

Start Byte LengthAddressCommand HighCommand  LowDataEnd 

State Change Reports 

The ADP120/ADP102 may also be configured to send a report to the host system whenever an input changes state, or a  counter overflows (reaches the maximum value of 2^32 and resets). These reports are formatted as responses  to the input “Get State” command (​0x8101 [Address] [State] 0x13​). They may be enabled or disabled via their  respective configuration bits in each pin’s configuration. 

Sample Code (Python)

''' Example usage of the ADP120 DIO expansion card '''

import sys
from time import sleep
import functools

from serial import Serial  # python -m pip install pyserial

# Detecting serial port
import serial.tools.list_ports as system_ports

def get_device_port() -> str:
    ''' Scans system to detect device CDC ACM port '''

    all_ports = system_ports.comports()

    for port, _, hwid in sorted(all_ports):
        if "1FC9:0094" in hwid:
            # Replace with "15A2:0300" if using ADP102
            # Fix for windows COM ports above 10
            if 'win' in sys.platform:
                return "\\\\.\\" + port
                return port

    return None

class PinConfig:
    ''' Pin configuration; used to set or report a pin config

        state_change:            Report to host when pin state has changed
        counter_overflow:        Report to host when pin counter has overflown
        starting_state:          Initial pin state
        enable:                  Enable/disable pin


    def __init__(self, state_change=False, counter_overflow=False, counter_polarity=0, latch_polarity=0,
                 starting_state=0, enabled=True):
        self.state_change = state_change
        self.counter_overflow = counter_overflow
        self.counter_polarity = counter_polarity
        self.latch_polarity = latch_polarity
        self.starting_state = starting_state
        self.enabled = enabled

    def bytes(self):
        nbytes = [0x00, 0x00, 0x00, 0x00]

        if self.state_change:
            nbytes[2] |= 0x02

        if self.counter_overflow:
            nbytes[2] |= 0x01

        if self.enabled:
            nbytes[3] |= 0x01

        if self.starting_state:
            nbytes[3] |= 0x04

        if self.latch_polarity:
            nbytes[3] |= 0x40

        if self.counter_polarity:
            nbytes[3] |= 0x80

        return bytes(nbytes)

    def from_bytes(nbytes):
        nbytes = list(nbytes)

        config = {
            'state_change': True if nbytes[2] & 0x02 else False,
            'counter_overflow': True if nbytes[2] & 0x01 else False,
            'enabled': True if nbytes[3] & 0x01 else False,
            'starting_state': True if nbytes[3] & 0x04 else False,
            'latch_polarity': True if nbytes[3] & 0x40 else False,
            'counter_polarity': True if nbytes[3] & 0x80 else False,

        return PinConfig(**config)

class ADP120(Serial):
    ''' Subclass serial with ADP120 specific commands '''

    START = b'\x24'
    END = b'\x00\x80\x01'
    COMMANDS = {
        'model': b'\x00\x00\x01',
        'serial': b'\x00\x00\x03',
        'read_state': b'\x01\x01',
        'read_latch': b'\x01\x02',
        'read_count': b'\x01\x03',
        'clear_latch': b'\x01\x04',
        'clear_count': b'\x01\x05',
        'toggle_output': b'\x01\x09',
        'save_config': b'\x00\x06',

    def __init__(self, *args, **kwargs):
        ''' Initialize serial device; set port timeout if missing '''
        if 'timeout' not in kwargs:
            kwargs['timeout'] = 5
        if 'write_timeout' not in kwargs:
            kwargs['write_timeout'] = 0

        super(ADP120, self).__init__(*args, **kwargs)

    def command(self, cmd: bytes, adr=None) -> bytes:
        ''' Send and ADP120.COMMAND to the hardware device '''
        if adr is None:
            return self.write_command_raw(cmd)
            return self.write_command_raw(bytes([adr]) + cmd)

    def read_response(self) -> bytes:
        ''' Read the response to a command '''
        r = self.read(1)
        if r == self.START:
            rlen = self.read(1)
            return self.read(ord(rlen) - 1)[3:]
            return self.read(self.in_waiting)

    def write_command_raw(self, cmd: bytes) -> bytes:
        ''' Write the raw bytes to the serial device '''
        # Raw command
        raw = self.START + bytes([len(cmd) + 1]) + cmd

        # Write the command
        count = self.write(raw)

        # Check whole command was written
        if count != len(raw):
            return None

        # Get the response
        reply = self.read_response()

        return reply

    def write_config(self, address, config):
        ''' Configure a pin '''
        return self.write_command_raw(bytes([address]) + b'\x00\x05' + config.bytes())

    def read_config(self, address):
        config = self.write_command_raw(bytes([address]) + b'\x00\x04')

        return PinConfig.from_bytes(config)

    def write_output(self, address, state):
        return self.write_command_raw(bytes([address]) + b'\x01\x08' + bytes([state]))

    # Support ADP120.model() syntax
    def __getattr__(self, name):
        cmd = self.COMMANDS.get(name)

        if cmd is None:
            raise AttributeError(name)
            result = functools.partial(self.command, cmd)

        return result

if __name__ == "__main__":
    port_name = get_device_port()

    # Detect the ADP120 module
    if port_name is None:
        print("Failed to detect device!")

    adp = ADP120(port_name)

    # Report model and firmware version
    print(f"Model: {adp.model()}")

    # Read input and output states
    for i in range(0, 8):
        print(f"{'Input' if i < 4 else 'Output'} {i if i < 4 else i - 4} State: {adp.read_state(i)}")

    # Read the config of output 0
    cfg = adp.read_config(4)
    print(f"Output 0:\n  Starting state: {cfg.starting_state}\n  Enabled: {cfg.enabled}")

    # Toggle the starting state, and enable the port
    cfg.starting_state = False if cfg.starting_state else True
    cfg.enabled = True
    adp.write_config(4, cfg)

    cfg = adp.read_config(4)
    print(f"Output 0:\n  Starting state: {cfg.starting_state}\n  Enabled: {cfg.enabled}")

    # Write an output and confirm it worked
    adp.write_output(4, 1)
    print(f"Current State: {adp.read_state(4)}")
Updated on May 21, 2024

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