Watchdogs redux
Parting thoughts
If you're building an electronic toothbrush, watchdogs are probably not terribly important. But an automated reset helps boost consumer confidence in our products' quality. Everyone hates the "remove batteries and wait 30 seconds" dance.
Many vendors are putting more thought into their WDT designs; some are doing a pretty good job. But we have a long way to go, and the wise developer will apply sound engineering practices to this often-neglected part of the system.
The article I cited shows that some ingenious approaches are being used. Consider adding a bit of hardware support if robustness is an important requirement.
Jack Ganssle (jack@ganssle.com) is a lecturer and consultant specializing in embedded systems' development issues. He has been a columnist with Embedded Systems Design and Embedded.com for over 20 years. For more information on Jack, click here.
Endnotes:
1. Ganssle, Jack. "Born to Fail" Embedded.com, December 12, 2002. Available at www.eetimes.com/4024495.
2. Texas Instruments. "MSP430x5xx/ MSP430x6xx Family User's Guide" Literature Number: SLAU208H, June 2008–revised December 2010. Available at http://focus.ti.com/lit/ug/slau208h/slau208h.pdf
3. Freescale Semiconductor. "MCF51QM128 Reference Manual: Supports the MCF51QM32, MCF51QM64, and MCF51QM128," Document Number: MCF51QM128RM, Rev. 0, November 11, 2010. http://cache.freescale.com/files/32bit/doc/ref_manual/MCF51QM128RM.pdf
4. Shankar, Karthik and Roman Lysecky. "Control Focused Soft Error Detection for Embedded Applications," IEEE Embedded Systems Letters, December 2010, Volume 2 Number 4.
5. The Nexus 5001 Forum—A Program of the IEEE–ISTO. See http://www.nexus5001.org.
6. "CoreSight Program Flow Trace Architecture Specification, v1.0." ARM, 2008. Available at http://infocenter.arm.com/help/topic/com.arm.doc.ihi0035a/IHI0035A_coresight_pft_architecture_spec.pdf.
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