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tidud25a problem regarding LC sensor

Other Parts Discussed in Thread: CC1310, TIDA-01228

Dear Sir,

I have asked some question about the tidud25a before,

recently, i need to go implement more test on it ,

my test board was CC1310 Launchpad and custom LC board (mainly refer to the given schematic)

for the pdf , i refer to

for the schematics ,

i refer to the one used in

i have encounter some new problem and would like to ask .

here is my question:

1) I have test the two inductors case, i find the waveform is a bit strange as follow:

this is one of the waveform i captured from the point of the receiver leg of CC1310,

which i think is ok or good.

However, some other waveform appears is not good?(but it still return the tick value)

and for the second question:

2) For the sampling rate , in P.6 Section 2.3.3 it mentions about it, and i have changed the value(RTC ?) from default 16 to above,

so is the RTC value in CCS equal to the sampling rate ?

And when i increase the value, the overall EFF count give more error, how can i solve it?

3) in the scs, it have a variable call LUT , and it is 16(default),

the desciption of it is Length of Tables for counters (Up,down, error), can you explain more what is it?

thanks

Jeff

  • Jeff,

    on1)

    yes, the 1st oscillation form looks perfect. The other plots you provided are not good - you need to fix the second inductor form. I gave you some advice before what you could try - did that help?

    The 2nd plot which is not good but still returns the tick value: yes, that happens because we count the times the threshold of the internal COMPA reference was reached. In your plot it seems that the 1.27 Volt REF value is crossed in every cycle, even if the LC-oscillation is not to the maximum as it should be.

    Same applies for the 3rd plot (though i don't know why you have shorter oscillation period than in the 2nd).

    The 4th plot is not clear to me, that is definitely not good for LC-oscillation (may be you get some external influence from the LCD?).

    on 2)   scifStartRtcTicksNow(0x00010000 / 16); 16 Hertz default sampling rate

    This line defines in the CCS project the sampling rate which the SCE will run with.

    If you do   scifStartRtcTicksNow(0x00010000 / 64);

    then you will have 64 Hertz sampling rate.

    Yes, if the 2nd Inductor doesn't oscillate properly, then increasing the sampling rate will give you more effCount errors.

    Solving this means we have to solve the 2nd inductor oscillation (make it be like the first inductor), then the errors will be minimized.

    on 3) LUT =LookUpTable. I need some time to look into this and will come back to you in a few days.

    Regards,

    Milen

  • Dear Milen,

    Thanks for your quick reply.

    I have done some work today and have some updated question,

    1) i think the previous question was

    and the updated strange no good waveform was a little bit different.

    Whatever, i follow your suggestion and the task description to separate the distance between the inductors and now the waveform become

    i observe that the waveform have great difference in the duration ,  what do you think the reason making it?( i think i have 3 LC setup equally

    2)

    on 2)   scifStartRtcTicksNow(0x00010000 / 16); 16 Hertz default sampling rate

    This line defines in the CCS project the sampling rate which the SCE will run with.

    If you do   scifStartRtcTicksNow(0x00010000 / 64);

    then you will have 64 Hertz sampling rate.

    because i need to plot it to ccs and i have done it.

    in which way i can tell my "M3" to increase the sampling rate ? is that i set a task or a interrupt flag in sce(e.g. in case i detect a change in the effcount ) to alert my M3 to do so ? and then switch back to low sampling rate if i want to conserve batteyr life?

    3)

    and for the LUT , i find that it is the lookup table relating to the init. section in the scp.

    thanks

    Jeff

  • HI milen,

    any insight about my new problem?

    thanks

    Jeff

  • Jeff,

    on 1) it seems you control all 3 LC sensors - this is NOT needed. I tested with 2 LC sensors, the 3rd one is optional only! So select the 2 sensors with good waveform and forget (do NOT use the 3rd)!
    Based on your report you have two identical waveforms and the 3rd which is longer (ignore this one).

    on 2) absolutely correct, if the SCE detect may be half-disc rotation (to be sure you are not having some jittering back and forth) or you see an errorLUT then you increase the sampling rate.
    After you detect some period of no changes (could be 1sec or more or less, based on your judgement and application needs), you go back to power save mode with lower sampling rate.

    on 3) correct, errorLUT contains 16 lines of PrevState-newState for the L1L2 inductors. If you go from 00 to 11 you have two changes at the same time - this is an error!
    Because in the proper case, only one inductor should change state as the disc is turning.
    Hence, 8 lines in the errorLUT have value = 0 (good cases) and the other 8 are equal 1 (error occured).

    Let me know if your code with 2 LC-sensors works!
    Regards,
    Milen

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