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The little big difference

posted Nov 15, 2012, 1:53 AM by Daniel Berenguer   [ updated Dec 10, 2012, 7:22 AM ]
panStamps are now even lower power. Our wireless modules now include a 32.768 KHz crystal connected to the XTAL/TOSC pins, making panSTamps consume as low as 1 uA in those battery-powered applications requiring the module to wake up periodically. Moreover, the new crystal is used at start-up to calibrate the internal RC oscillator. A big difference in power consumption (5uA vs 1uA) and precision (uncalibrated vs calibrated oscillator) made by a small part.

But how does this affect our programs? What if we own the version of panStamp without the crystal?

config.h (from the Arduino panStamp library) includes the following definition:

 * External RTC crystal (32.768 KHz)

EXTERNAL_RTC_CRYSTAL is disabled by default so in case you own the old modules you won't have to modify anything. However, for the new version you may enable this option in order to take advantage of the whole low-power potential of your panStamps.

From no on, EXTERNAL_RTC_CRYSTAL is enabled by default from config.h. This option needs to be disabled for old versions of panStamp.