Mbed Client Lite: Robust management of constrained devices

The IoT landscape spans multiple verticals and a varied range of use cases. As a result, IoT device types also differ widely, from very constrained and low-cost sensors to more expensive and complex devices.

Mbed Cloud provides powerful device management capabilities to handle this diverse landscape by supporting multiple Mbed Cloud client profiles to address the various requirements and constraints of different IoT devices.

Mbed Client Lite is the client profile for constrained devices - specifically, cost-sensitive devices that lack code space and processing capabilities.

These devices typically serve single-function applications with possible multiple sensors/actuators and their data processing and operations capability is limited to:

  • Sending/receiving statuses/commands
  • Sending/receiving data
  • Simple data pre-processing (e.g. averaging, min/max and filtering)
  • Simple decision-making, context-helped

Example applications exist in multiple vertical solutions, including:

Logistics/Shipping - pallet tracking sensors

Hundreds of millions of pallets are in transit worldwide at any given time, carrying products of all sorts. In many cases, the products they carry are sensitive to environmental conditions. Smart pallets enabled with location and environmental sensors could reduce losses associated with lost or spoiled items. But pallets are very cost sensitive, so any sensor added to a pallet to track its location and environmental conditions must use minimal code space and processing capabilities, to keep power consumption low.

Fluid valve audio sensor for state and predictive maintenance

Many industrial machines use valves to control flow of fluids and gasses in the production lines. Accurately sensing the valves' state is critical for controlling the system, but the mechanical sensors currently in use suffer from multiple flaws, and any replacement for them needs to support the smallest code space and processing requirements possible to keep power consumption low. To address this, new audio sensors are being used on production lines to collect the audio samples generated by the valve and process them through filtering and compression to detect the valve state more accurately. More complex data processing in the cloud can also be used for predictive maintenance, detecting problems in advance and preventing malfunctions. These IoT devices are also cost-sensitive, with limited code space and processing capabilities.

Difficulties with constrained devices

Although constrained, these devices can still directly communicate on an IP network and support the security functions required on a large network. Nevertheless, due to constraints, these devices are only capable of using protocol stacks specifically designed for constrained nodes (such as CoAP over UDP/DTLS) and cannot employ the full internet protocol stacks such as HTTP and related security protocols and XML-based data representations.

Addressing these challenges

Mbed Client Lite profile offers many benefits:

  • Easy to use - Out of the box solution pre-integrated with Mbed OS.
  • Support for protocol stacks specifically designed for constrained nodes CoAP over UDP - CoAP is designed to use minimal network and device resources, utilizing fixed headers and compact encoding to enable short messages and cause less fragmentation.
  • Supports channel security (DTLS – PSK) - Establishing channel security over UDP is possible using DTLS and for even lower footprint it was chosen to utilize its Pre-shared-key (PSK) profile instead of using its certificate based profile.
  • Supports remote secure firmware update - New software versions for the device are expected, in order to fix bugs, security flaws and add new features of our application. These devices are cheap and it is commonly assumed that simply replacing them is the right approach. The total cost of replacement must be considered, since sending a technician can cost more than the device itself. Therefore, updating the device software remotely and securely is critical for large scale deployments.
  • Low footprint leaves more space for your application - Mbed Client Lite and Mbed OS are designed to only account for up to 50% of the constrained device available resources.
  • Required ROM and RAM numbers -
    • Memory (RAM) 64 KB: Mbed Client Lite, Mbed TLS and Mbed OS use about 36 kB.
    • Storage (ROM) 256-512 KB: Mbed Client Lite, bootloader and Mbed OS use less than 180KB.
    • Additional block storage required for firmware update to store the download image.
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