Use Watchdog Timers (EE Tip #143)

Watchdog timers are essential to many complete electronic system designs.  As Bob Japenga explains, following a few guidelines will help make your designs more effective.

No longer used in just the realm of fault-tolerant systems, independent watchdog timers are put on systems because we know something can go wrong and prevent it from being fully functional. Sometimes the dogs reset the processor and sometimes they just safe the device and notify a user. However they work, they are an essential part of any system design. Here are the main guidelines we use:

  • Make it independent of the processor. The last thing you want is for the processor to lock up and the watchdog to lock up too.
  • Do not tickle the watchdog during an interrupt. (The interrupt can keep going while a critical thread is locked up.)
  • Do not tickle the watchdog until you are sure that all of your threads are running and stable.
  • Provide a way for your debugger to have break points without tripping the watchdog.
  • If the watchdog can be disabled, provide a mechanism for this to be detected.

I provide many more guidelines for watchdog design in a white paper that’s posted on our website.—Bob Japenga, CC25, 2013

Compact Computer-on-Module

ADLINKThe cExpress-HL computer-on-module (COM) utilizes an Intel Core processor (formerly known as Haswell-ULT) to provide a compact, high-performance COM solution. The cExpress-HL is well suited for embedded systems in medical, digital signage, gaming, video conferencing, and industrial automation that require a high-performance CPU and graphics, but are constrained by size or thermal management requirements.

The cExpress-HL features a mobile 4th Generation Intel Core i7/i5/i3 processor at 1.7 to 3.3 GHz with Intel HD Graphics 5000 (GT3). The COM delivers high graphics performance while still keeping thermal design power (TDP) below 15 W. Intel’s system-on-chip (SoC) solution has a small footprint that enables it to fit onto the 95 mm × 95 mm COM.0 R2.0 Type 6. The COM provides rich I/O and wide-bandwidth data throughput, including three independent displays (two DDI channels and one LVDS), four PCIe x1 or one PCIe x4 (Gen2), four SATA 6 Gb/s, two USB 3.0 ports, and six USB 2.0 ports.

The cExpress-HL is equipped with ADLINK’s Smart Embedded Management Agent (SEMA), which includes a watchdog timer, temperature and other board information monitoring, and fail-safe BIOS support. SEMA enables users to monitor and manage stand-alone, connected, or remote systems through a cloud-based interface.
Contact ADLINK for pricing.

ADLINK Technology, Inc.
www.adlinktech.com