Hi Nick, That is not correct. You cannot sample the AnEx (ADC0 and ADC7) channels at the same time as the battery voltages and would need to be multiplexed. The acceleration data is read on different ADC channels so they can be read simultaneously with the battery data (or close enough).
However, one thing to note is that there is some crosstalk between one of the acceleration channels (z-axis) and one of the voltage measurements (VSenseBatt). This can influence the battery reading by 5-6% on average and up to 10% in extreme cases. There are a couple of ways of dealing with this crosstalk (but it's not something I've had a chance to play around with myself): 1. SW averaging (100 to 1000 counts) to the battery measurement as accel. signals are quasi-periodic assuming the user isn't in an elevator or vehicle. 2. VSenseBatt - n * Zaccel = VSenseBatt_correct. The scaling factor (n) would need to be determined experimentally. The other option would be to put the z-axis line into GIO output mode and drive it low when you want to measure the battery voltage. The best solution for you is going to be very much dependent on your application's specifics. Mike On Mon, Apr 23, 2012 at 7:05 AM, Nicholas Hosein <[email protected]>wrote: > Just to clarify. If the battery monitoring is enabled on the shimmer with > the SET_PMUX_COMMAND and acceleration data is being collected > simultaneously the resultant output should be garbage? In order to get the > battery state while collecting data I need to modify the boiler plate app > to multiplex the two signals. > > Best, > > Nick > > > On Mon, Apr 16, 2012 at 1:07 AM, mike healy <[email protected]> wrote: > >> Hi Nick, >> >> Enabling the voltage monitoring is available in >> ShimmerConnect/BoilerPlate. When you got to Tools->Configure Shimmer you >> will see an option that says "Enable Voltage monitoring". This will change >> the "AnEx ADC0" and AnEx ADC7" channels to "VSenseReg" and "VSenseBatt" >> respectively. Specifically the "SET_PMUX_COMMAND" in BoilerPlate manages >> the state of this mux: >> http://tinyos.cvs.sourceforge.net/viewvc/tinyos/tinyos-2.x-contrib/shimmer/apps/BoilerPlate/Shimmer.h?content-type=text%2Fplain >> >> The part that has not been implemented is to toggle this option quickly >> in order to inter-space voltage monitoring with measuring the external ADC >> channels, or any method to convert the difference between the two voltage >> measurements to instantaneous current (as described in the manual). >> >> Mike >> >> >> >> On Sat, Apr 14, 2012 at 1:48 AM, Nicholas Hosein <[email protected]>wrote: >> >>> Does the boiler plate app have this implemented by chance? or does the >>> shimmer connect software use something besides the boilerplate. >>> >>> Much Thanks, >>> >>> Nick >>> >>> >>> On Fri, Apr 13, 2012 at 1:15 AM, mike healy <[email protected]>wrote: >>> >>>> Hi Nick, >>>> >>>> The battery monitoring is multiplexed with the two ADC channels exposed >>>> on the external connector (i.e. ADC0 and ADC7). So you cannot sample the >>>> battery voltages and these channels at the same time. But you can switch >>>> between the two of them quickly if required. >>>> >>>> See section 2.4.4. of the Shimmer User Manual for further details. See >>>> the FAQ page to see how to convert the raw ADC value you receive back to >>>> battery voltage: http://www.shimmer-research.com/links/faqs#S9. >>>> Remember to double the value due to the halving of the voltage before it is >>>> measured (as mentioned in the referenced section in the manual). >>>> >>>> Mike >>>> >>>> On Wed, Apr 11, 2012 at 7:37 AM, Nicholas Hosein >>>> <[email protected]>wrote: >>>> >>>>> I noticed that the shimmer software can access the batter state on the >>>>> mote. In my experience the battery monitor and data bus share the same bus >>>>> so battery updates cannot be made while collecting data (I could be wrong >>>>> about this though). Was there an update to the boiler plate app that >>>>> allows >>>>> battery monitoring (by percentage or voltage) in realtime while collecting >>>>> data? >>>>> >>>>> Much Thanks, >>>>> >>>>> Nick >>>>> >>>>> _______________________________________________ >>>>> Shimmer-users mailing list >>>>> [email protected] >>>>> https://lists.eecs.harvard.edu/mailman/listinfo/shimmer-users >>>>> >>>>> >>>> >>> >> >
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