Posts by Kenneth MacCallum

Using Matched Filters  Anyone who has taken a signals and communications course has likely heard of matched filters. Intuitively these filters use knowledge of the form of a transmitted signal to pull it out of the noise. Matched filter theory or related concepts are commonly used in RF communication but I often apply it to […]

In many medical devices, especially those that are microprocessor controlled, it is common for programmable subsystems to communicate via asynchronous serial protocols. Such subsystems include things like programmable power supplies, syringe pumps, temperature controllers, motor controllers and smart linear actuators. I’m often surprised by how many of these devices have poorly thought-out protocols that make it […]

Lithium rechargeable batteries achieve some of the highest energy densities available today. Not surprisingly, medtech companies are keen to use lithium batteries in medical devices and benefit from reduced weight or increased battery life. There are a number of safety implications to choosing these batteries as well as practical business implications.

Digital Health: Floating Away Until very recently I would never have dreamed of using floating point computations in firmware. It required too heavy a penalty in code space and computation time. Suddenly the game changed considerably.  Now there are a number of relatively inexpensive microcontrollers which have single-precision floating point capabilities implemented in hardware. Here […]

Toyota’s recent $1.5 million jury awarded loss in an Oklahoma court illustrates it’s pretty much impossible to write software without some third party code creeping in.  IEC62304:2006 calls this “Software of Unknown Provenance” or SOUP, referring to software with unknown safety-related characteristics, or developed under an unknown methodology.  I know the situation very well.  Operating Systems, code libraries […]