Curious about current draw experiences

My wixel app is being powered by a single LiPO cell, which will present anywhere from about 4.2 V down to 3.4V during its useful life. This particular app only transmits, but does so quite frequently, with transmission events occurring based on sensed changes. Anyway, I have used well over 2 dozen wixels and have never seen one draw more than about 8MA, confirmed both by direct measurement as well as the battery longevity. The docs say significantly hight current should be expected. So has the wixel circuit or MCU itself been improved since the original doc files were written, or am I just lucky? I certainly am using a lot of features, including A/D readings which I understand to add to current draw. I’ve also used the USB for diagnostic output, with the +5 line open. Still barely more than 8mA.


The CC2511 datasheet shows higher current draws when the radio is transmitting data. I suspect your low current draw is due to the rate you are transmitting at. How often are you sending data? What baud rate are you using?

- Jeremy

Hmmm… well I’m not using any serial port emulation. My transmissions are short (perhaps 22 bytes plus overhead) binary structures, mostly based on the low level example in your “test_radio_signal” example. So its hard to say what the equivalent low level RF modulation equivalent of a baud rate would be. Its basically as fast as the packet can be sent.

As far as transmission rate over time time, if the app has not detected changes in the data I’m sending, i just send one packet about every 1/2 second. There is no “turn around” to receive an acknowledge, its almost more like UDP data gram scheme… just keep sending with some repeats to add reliability, and the usual message ID to the receiver can tell whats new and what’s just repeats. But, if data changes are detected in my application, I’ll send out as many as 10 such packets perhaps 10mS apart, plus whatever recovery overhead the radio calls require. And even when I force continual changes, it barely adds a milliamp or so avearage. Still a long way from the near 30mA in the docs.

Don’t get me wrong… I’m not complaining! :slight_smile: The app will run over 18 hours on a little 200mAh LiPO cell, before my battery protection circuit kicks in to shut things down. But I just thought maybe some improvements were made in the MCU itself since the first Wixel inception.