MicroSAM Overview

This specification defines a new form-factor that is targeted at helping traditional sensor vendors quickly create smart sensors without having to worry about the control domain of the sensor.  The Micro Sensor Adapter Module (MicroSAM) is a compact computing module developed specifically to meet the needs of sensor-domain control within the Industrial Internet of Things (IIoT) application space.

MicroSAM fills a need not currently addressed by other PICMG specifications; namely, a compact module targeted at microcontrollers within a sensor domain.  As such, the processing performance, and I/O connectivity are targeted toward sensor interface.  MicroSAM may exist in parallel with other PICMG technologies, where MicroSAM devices provide sensor connectivity, and MicroTCA®, COM Express®, or CompactPCI® Serial provide higher layers of control.

This specification recognizes the availability of many microcontroller-based open-sourced platforms.  MicroSAM extends and co-exists with this ecosystem by offering a standards-based solution that has been designed specifically for embedded use.  Industrial environmental operating range, power filtering and robust connectors are some of its key advantages.

MicroSAM Objectives

This specification has been developed in order to benefit the industry in three specific ways.  These are:

  1. To enable sensor vendors to create smart sensors without having to manufacture the control circuitry and/or software by purchasing these components from PICMG-compliant suppliers.
  2. To enable controller suppliers who wish to create smart sensors or smart-sensor components to do so in a way that is interoperable with other suppliers.
  3. To accelerate the uptake of smart-sensor technology through open-specifications and interoperability.

When combined with the PICMG sensor-domain network architecture and data model, sensors connected to MicroSAMs will seamlessly integrate into the network with plug-and-play interoperability.

Overview of Sensor Node

A sensor node is a single physical endpoint within the IIoT network. Its purpose is to interface directly with a sensor (e.g. temperature sensor, pressure sensor) or effector (e.g. servo motor, solenoid), and provide a means for higher levels of the installation to read and modify the status of the connected sensor/effector. The sensor node must be capable of self-reporting its capabilities in such a way as to provide plug-and-play with the rest of the network.

In addition to operating as an isolated endpoint, some use cases may require multiple endpoints to work together in a coordinated fashion. A typical example of this is multiple axis motion control where each sensor node controls a single motor but motors must begin precisely at the same time. Coordination of these motions requires signaling from a synchronization node to each of the synchronized endpoints.

For applications with safety requirements, such as robotic arm control, an additional safety interlock may be required in order to shut off the control output without the necessity of intervening software.

The MicroSAM is a specific implementation for a generalized “Smart Sensor End-Point” that allows integration of low-level sensors and effectors into a complex plant control network. The context in which a MicroSAM device operates is shown in Figure 1.

The MicroSAM module sits between one or more Sensors and/or Effectors, intended to provide measurement and/or control of some aspect of plant operation, and an “Aggregator”/”Bridge” that manages the MicroSAM/Sensor/Effector operation directly and/or connects the MicroSAM to the higher-level plant network. Communication between the MicroSAM and the Aggregator/Bridge flows through a point-to-point channel in order to minimize the complexity and size required for processing elements within the MicroSAM – they are not, for example, required to support an Ethernet PHY and/or an IP network stack.

The MicroSAM manages sensor/effector sampling and formats the sensor/effector data for presentation to the network; an Aggregator coordinates the activities of multiple MicroSAM modules; a Bridge interconnects the MicroSAM point-to-point communication channel with a higher-level shared network.

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Key Benefits and Features

The basic features offered by MicroSAM are:

  • Full industrial operating temperature range from -40C to +85C.
  • Power filtering and signal conditioning for embedded installations
  • RS422 communications link for reliable communications
  • Direct connectivity to a variety of sensor types (analog voltage, analog current, digital)
  • Latching connectors for secure connectivity
  • PWM output for motion control applications
  • Hardware interlock and trigger signals for synchronization
  • Small size (32mmx32mm)
  • Low power consumption

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