Congratulations Anders. This is a great article. Low power Touch sensing is becoming the best choice for user interface. Check out Freescale new Kinetis L series (Cortex M0+) family with Touch sensing module.
Hi Dr DSP,
Actually the decoder in LESENSE can operate on any signals from the PRS (peripheral reflex system), this means even signals directly from GPIO or even serial packets from a low energy uart. Since the decoder is able to do simple logic functions and operate like a kind of state machine you can do packet decoding or logic functions consuming only a couple of uA. The LESENSE decoder can also trigger events through the PRS, this means that you can trigger timers, initiate DMA transfers, start ADC conversions etc. as you describe.
Also, because of the 2 us wake up time, if you need to do more advanced calculations it can often be more energy efficient to wake up the cpu for a short period (some microseconds).
Doing work without waking the CPU is a good feature. What I'd like to see is a small amount of programmable logic that can be used to do very low power simple logic functions that can then be used to wake the CPU (or initiate a DMA transfer, start an AtoD conversion, check the destination address of a serial peripheral data packet, etc.) Now that could offer REAL power advantaged!
Anders demonstrates a capacitive example here: only when a given gesture is done on the starter kit, much like slide opening a smartphone, the Cortex-M3 CPU will be woken up to process data. Smart monitoring does help battery operated apps to longer life between e.g. each charging.
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