Embedded System Development for Imaging System

Client – Medical imaging device manufacturer

Capabilities Demonstrated

  • Embedded hardware development

  • Embedded software/firmware development
  • FPGA development
  • Mixed-signal circuit board design and PCB layout

  • Real-time video image pipeline processing
  • Motion control
  • Windows kernel device driver and application software

Challenge

The client had identified several “show-stopper” issues (including various image artifacts and other reliability concerns) with their “production intent” design.

At that time-critical juncture, they asked AppliedLogix to jump in and critically assess the system design end-to-end, generate a findings and recommendations summary, and then proceed to modify and enhance the design as needed to make it truly production-ready.

When developing a product, it’s super important that everyone works closely together, as a unified team, regardless of whether that team is spread across multiple companies or all in-house. In this case, it was even more important because we were dealing with the regulated world of medical devices, where the development processes are often more rigorous. From the start, the AppliedLogix team integrated its efforts within and under the client’s ISO quality process. Thereby avoiding any new speedbumps within their FDA 510(K) approval process.

The AppliedLogix team needed to:

  1. quickly and comprehensively evaluate the failure modes,
  2. brainstorm and nail-down the root causes,
  3. and then develop a targeted set of design updates to make it production-ready.

AppliedLogix assembled a multi-functional team, deployed onto the customer’s site, and then built-out a “war-room” of sorts to maximize the daily flow of information and accelerate the entire process. The team operated across multiple engineering domains in-parallel: hardware, software, FPGA, and firmware. A lot of pieces needed to come together quickly and all play nicely together.

Solution

The AppliedLogix team completed, what is best described as a complete revamping of the embedded hardware and software, in 3 phases:

  1. Detailed assessment/analysis coupled with system design modifications recommendations
  2. Design execution of the full set of “production intent” HW and SW updates
  3. Rigorous performance testing followed by “final production” design updates

Benefits

A combined team effort between the client and AppliedLogix led to a final production design that met all of its operational and performance targets, enabling a successful product launch  (this was the client’s first revenue-bearing product, so successful product launch was all the more critical).

System Overview

The initial launch device, targeted at clinicians, offered a “desk-side” confocal laser microscope platform, loosely tethered to a host PC/Windows platform. This revolutionary system delivered non-invasive, real-time imaging of human skin tissue at the cellular level. These unique capabilities enabled scientists and physicians to characterize cellular structures that are otherwise invisible to the naked eye.

The key functional design elements for the embedded controller subsystem included:

  • Motion control loops and related processing for:
    • Galvanometer-based slow scan direction beam deflection
    • Polygon-based fast scan direction beam deflection
    • Z-axis servo motor control to establish and maintain the desired focal plane
  • Photomultiplier tube (PMT) based imager
  • Target illumination selectable via 1 of 3 DAC channels driving unique wavelength S-type laser diodes
  • Raster image synchronization and capture
  • Image serialization and transmission to the host system

In addition to the embedded controller subsystem, a custom PCIe-based host interface card and associated device driver software were also designed. This card (10-layer, controlled impedance) was FPGA-based with local DDR3 memory for the image path buffering and control.

Software Developed

  • Image/data acquisition
  • Image acquisition state machine
  • PID loop for auto image control
  • Supervisory state machine
  • System calibration routines
  • End-of-line custom functional test
  • Windows kernel device driver
  • Application Programming Interface library

Hardware Developed

  • FPGA + ARM microcontroller working in tandem
  • Mixed-signal, 10-layer, controlled impedance PCB
  • Precision analog – multiple ADCs / DACs
  • Integrated motor controllers
  • Proprietary high-speed serial image transfer link
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