Thanks mike that makes sense. As far as interfacing to ADC 0/7 I dont see anything in the READ_ME or the shimmer manual which explains how to use the SET_PMUX_COMMAND. From the BoilerPlaceC.nc code I can see that SET_PMUX_COMMAND needs one argument but it doesnt explain what this argument is.
>From my limited understanding it seems like after I set the PMUX the ADC 0/7 will have the battery voltage which will be sent over bluetooth in the same packet as the acc/gyr/mag. Also from the readme im assuming the packet will look like this: [PacketType | TimeStamp | BatteryMSB | Acc ... Mag | BatteryLSB] Or am i confusing the ADC number with channels? Much thanks, Nick Nick On Mon, Apr 23, 2012 at 12:42 AM, mike healy <[email protected]> wrote: > 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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