Mean time between failure made easy

In addition to size, weight, and power constraints, reliability is a key requirement of many embedded systems. A common way of measuring a design's product reliability is the mean time between failure (MTBF) calculation. Being able to accurately measure and report a product's MTBF has advantages: customers are generally willing to pay more for a product they can depend on and will purchase again from companies that produce reliable products.

But measuring MTBF usually involves adding parts, power, and another point of failure to an already densely populated design. Described here is a software-based method to track time-in-service and MTBF, using resources that already exist in most embedded devices. The additional software doesn't affect the MTBF of your design.

Top-level design
For the purposes of this article, an MTBF task (or more generically the task ) is defined as any message-based task in any modern embedded operating system. As described herein, the task uses a periodic timer and two 64-kbyte, byte-addressed flash sectors to track 31 years of time-in-service (TiS ) in one-minute increments, without affecting the flash memory's life. Figure 1 shows the top-level MTBF task design.

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