MSP430FR2512: inquiry about parameter setting issue with Captivate Studio

Hello,

Besides, I have another question about the captivate studio. After I connected the studio without pressing calibration, I'd like to know if the data from the plot is based on the parameters(like conversion gain) I set in programmed code or new parameters which created by the design centre itself according to the environment? Will the calibration happens automatically after 'connected'?  Can I trust the count value is got from my settings? And what if my parameters are not proper? During test, I found the count data is 1/4 lower than the conversion count  I set in parameters

B.R

FANS  

Hi Yuke,

Your conversion count is set to high

Try to reset all the settings and then set converison count to 1000

Regards,

Ling

Hi Ling,

Thanks but I'm still confused why conversion count should set to 1000, the value is from 100 to 8191(that is 2^13), and the count is the number of charge-transfers,right?

Q1: I haven't ticked recalibration and press calibration on GUI, then I wonder if the count value I read from GUI plot is just raw data of real transfered charge relate to switch freq and voltage only? Or does it has relation with parameters of signal conditioning (conversion count,gain and offset)?

Q2: Regarding the parameter, count value is judged by Voltage, switch freq, C external,C parastic and Csample, and I heard Csample is a fixed value.In that case, the parameter 'conversion count' seems just used to caculate the gain and offset and has nothing to do with actually transfered number of charge on Csample. Then question comes, I don't know real input Q(Ctouch+Cparastic), I don't know real Q(Csample) how do I know what's the proper conversion gain for setting? Unless the design center normalized the real Q(sample) to  my conversion count parameter and tell me the proper Gain  I need to set....Then I can set coarse gain and fine gain accordingly. If my understanding is true, why can't I set conversion count much higher to have better resolution?

Q3: I want to know the concept of conversion, that's not relate to charge transfer, just relate to data processing(some cacluation work like normalizing if I'm correct), so only have time cost for the whole system, right?

Q4: regarding conversion gain and offset parameter value setting ,does it operate to increase sensitivity like follows:

example: if Q(touch Cap) is 10,Q(parastic Cap) is 100, Q(sample Cap) is 1000(conversion count parameter), then in ideal situation, converion gain set to 15, with offset:(10+100)x15-1000 =650. Probility of Q(touch)before = 9.09%, Q(touch)after = 150/1000 = 15%(improved) ,if that's true, the offset may not only be the Q of parastic cap？

Could you please help for my questions?Thanks!

B.R

FAN

Hi Yuke,

For detail operation theory, please refer to CapTIvate technology guide:

http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/CapTIvate_Design_Center/latest/exports/docs/users_guide/html/CapTIvate_Technology_Guide_html/markdown/index.html

Or from your CapTIvate Design Center: Help -> Topic

Thanks,

Ling

Hi Ling,

I don't think that I haven't checked the Help doc.I have inquiry because I want to know more in detail.Could you please give me the link for the doc  for setting conversion count to 1000?Thanks!

B.R

FAN

Hi Yuke,

Would you please share your system requirement for the proximity sensor?

Thanks,

Ling

Hi Ling,

I use the silicon F430FR2512IRH to do Approximity sensor design for 5cm distance via CapTIvate center(studio), I need to test the raw count data from 20 C to 50C , we have prob that temperature will increase dramatically in a short time.During test  I find that the delta of  count value decrease dramatically with hot temperature compared with relatively cooling temperature point which makes it's hard to distinguish the real trigger for approximity with highest temperature such as 50C. I tried to improve this by increasing sensitivity and resolution by adjusting parameters.The proximity behaviour for my application is for long term proximity, which means detecting people proximity and stay (maybe distance will change during the stay but just can be considered in short time as noise). I want to set parameters for distinguish the poor count delta in hot temp point out by largely improving the resolution based on a high sensitivity. I don't think regularly adjusting LTA is a good idea because temperature can change rapidly or slowly judged by the weather, I hope to fix this by other way. Thanks!

B.R

FAN

Hi Ling,

Thanks for your share about LTA algorithm for temperature variation.BTW, do I have the possibility to disable integrated sampling capacitor or not?Thanks!

B.R

FAN 

Hi Yuke,

CapTIvate use charge transfer method to measure capacitance which means without internal sampleing capacitor it will not work.

Regards,

Ling