Debounce Noise
- reading-time:
1min19
- LinkedIn:
Everybody likes to push buttons. And every engineer knows you must debounce them to avoid noise. But who
decides how to do that? Is there a best strategy? Today we do a deep dive and consider all details that might be
architecturally important.
And, as we will see, we might even find some noise in the organization.
Roughly, there are two options: an (RC) filter in electronics or a bit of software — both with several variants. Both
an electrical engineer and an (embedded) software professional can implement them in a couple of hours.
But which technical solution is ‘the best option’? And what is ‘best’?
Suppose we are designing a high-volume, long-lasting, luxurious, self-powered device. This implies the ‘BOM’ should be
low, and that it runs for years on a battery, possibly using energy harvesting.
Now look at those buttons again: how can we minimize cost and power use at the same time?
Any solution with fewer components will be cheaper — that votes for a software solution. But software needs an active
processor — while low power calls for ‘deep sleep’. Polling the switch every 10ms will drain the battery!
A filter doesn’t use energy — unless the button is pressed.
Long story short: You need an estimate of how often & how long the buttons are pressed to calculate the µAh used every
day and per push. Also, technical details — like how the buttons are connected to the MCU and the exact (software)
algorithm — are needed to estimate how often the processor will be awake.
Then you can determine the best option!
There is one other option, with two possible outcomes — here comes the noise. Leave it to the two departments. Either
the engineers solve it, or the bureaucrats know it’s the other side’s issue…
Therefore, a great embedded systems architect will solve it long before that.
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