What’s the most efficient way to design the appropriate embedded logic into a laboratory device? More and more often, the answer is to use computer-on-modules, even for ARM-based designs. Heitec used an NXP i.MX6-based Qseven module from Congatec in the design of a spectro-photometric analyzer from Implen.

Spectrophotometric instruments for small-volume sampling are used in molecular biological, biochemical, and biomedical laboratories for a wide range of applications. The spectrophotometers are designed to perform different types of analysis based on very small samples. Examples include the measurement of protein and nucleic acid concentrations as well as the measurement of absorption and transmission characteristics. A company specializing in such analyzers is Implen, whose nanophotometers are mainly used for concentration measurements and quality control of nucleic acids and proteins in research and manufacturing.

Individual Functional Elements

The Implen NanoPhotometer® integrates a Qseven computer-on-module as the application-ready embedded computing core. (Credit: Implen)

The Implen NanoPhotometer® allows users to work with different sample sizes, depending on the application. The sample to be analyzed can either be placed directly onto the microvolume pedestal using a pipette or, alternatively, it can be measured in a temperature-controlled cuvette port. An integrated vortexer is used to mix the samples to obtain exact measurements. The results of the respective spectrophotometric procedure are automatically analyzed and graphically displayed on a touch screen.

Tablet PCs and smart phones can be connected via a Wi-Fi hotspot, while USB, WLAN, or Ethernet are available for Windows PCs. A large external screen can be connected via HDMI, and it is also possible to exchange data via a USB stick. The Linux-based system features an NXP i.MX6 ARM processor with 1 GHz performance for fast sample measurement, data processing, and visualization.

Computer-on-Modules — the Fast Track to Development

The NanoPhotometer® family from Implen is versatile and can be used in biological, chemical, medical, and pharmaceutical laboratories. (Credit: Implen)

Heitec implemented the appropriate embedded logic for Implen. For this purpose, Heitec used a Qseven computer-on-module as the application-ready embedded computing core and then developed the carrier board with the specific functionality required for the spectroscopic analyzer around this module. Such a combination lets developers enjoy both the design freedom of a custom-specific solution and the convenience of a fully developed and certified board while also enabling them to leverage the comprehensive ecosystem of SGET’s Qseven standard for the finished custom module.

The advantage: Custom modules and their ecosystem offer developers significantly more application readiness than any of the standard evaluation platforms for ARM designs, where support is frequently limited to allowing developers to copy existing circuit board layouts. They need to design everything else themselves. The carrier board option provides developers with flexibility, because it is less challenging to design than a full custom board. Essentially, it’s just a matter of routing the system interconnects and implementing the required additional controllers. What is more, with just one board design, developers can design scalable systems that are easily upgraded with newer processors. Thanks to standardization, there is no vendor tie-in.

The Customization in Detail

For the carrier board, compactness, cost, and energy efficiency each played an equally important role in the selection of the electronics and components such as the battery and heat management devices. In addition to all standard functions, such as touch controller interface, LVDS interface to the TFT panel, USB hub, and the integration of an external audio codec for provisioning an audio interface, the following special features were implemented:

  • Battery charge control for mobile use without power connection. A powerful 4S3P battery pack was installed, which allows the device to be operated without a mains connection for a whole working day and allows it to handle power consumption spikes when “pulling” measurements.
  • Standby control and soft on/off using a low-power FPGA because, unlike x86 processors, the i.MX6 has no deep-sleep function. The FPGA replicates the advanced configuration and power interface (ACPI), which is standard with x86, and switches off all current to the processor, thereby increasingthe availability of a nonconnected system from days to weeks. Thanks to quick boot, the processor can ramp up to full operation, including applications, within milliseconds.
  • Integrated motor control for the vortexer, including a “snubber” circuit to avoid unwanted system vibrations, which is key for the measurement of the absorption and transmission behavior of samples.
  • Controlled film heating as well as a special measuring bridge to the cuvette port to ensure highly accurate temperature measurement of samples, which is key for accurate analysis.

Overcoming the Space Shortage

Since there was scarcely enough space (200 × 200 × 120 mm, W × D × H) in the system to fit in all the offered functions, the Heitec developers had to work very closely with Implen’s mechanical design team and had to use thermal simulation to optimize cooling. The board was ultimately laid out in an L-shape and the Qseven module mounted on its head. The heat spreader, which matches the module, now contacts the metal bottom plate of the housing via a gap filler, while the remaining housing is mainly made of plastic. An additional heat sink within the battery charge control ensures efficient handling of this hotspot.

Heitec oversaw the complete supply chain management of the project and all production, as well as type testing and certification. So, the customer got compact and maintenance-free electronic assemblies (equipped boards) with comprehensive functionality from a single source. And even though Heitec was not required to ensure that standards were met for medical device development and production with batch traceability for this project, it was reassuring for the customer Implen to know that the company is trained to work in compliance with the high-quality standards for medical devices. Implen could rest assured that it would not be a challenge for Heitec to implement the Ethernet interface of the system in accordance with DIN EN 60601-1, which is required for a medical IoT application.

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