PSoC5 RTD filter

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shmc_934566
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Hello,

 

I am currently doing an RTD project using PSoC 5 and i am being hit with noise issues on longer PT100 lines. I have come accross the following document and i was wondering could someone enlighten me how to setup the DMA and filter etc. in this project https://www.cypress.com/file/102931/download.

Any help would be greatly appreciated

 

Regards

 

Shane

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odissey1
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shmc,

The example project shows use of DMA and hardware filter for demo purposes. The RTD measurements are likely performed at less of 1kHz rate, which does not need DMA. You can simply write ADC data into the Filter, and read it the result from the Filter using Filter API.

Another opportunity to improve S/N is to consider noise distribution properties. It is often that the noise is not normally distributed (not Gaussian), and is overloaded with occasional spikes. In such situation, a Median filter shows better performance than a linear filter, such as PSoC5 Filter. Check if this custom community component is improving your S/N (no DMA needed)

MedianFilter: sliding window median filter component 

/odissey1

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WaMa_286156
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shmc_934566
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thank you for these suggestions. I will take a look. These all seem to provide an output from the filter in terms of hardware. how would i view the filtered data in the code is what i am looking for.  this is so that i can then send the  temperature data out over LoRa

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Ekta_N
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Hello @shmc_934566 

You can refer to the following appnote: Link  which mentions in detail how a DMA controller (DMAC) in PSoC 5LP can transfer data from a source to a destination with no CPU intervention.

Best Regards
Ekta

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WaMa_286156
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If I Remember Correctly, the digital filter output is/can be DMA'd into memory to be used for other purposes.  You end up with an array of data that you can work on in your code.

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odissey1
Level 9
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First comment on KBA 1000 replies posted 750 replies posted

shmc,

The example project shows use of DMA and hardware filter for demo purposes. The RTD measurements are likely performed at less of 1kHz rate, which does not need DMA. You can simply write ADC data into the Filter, and read it the result from the Filter using Filter API.

Another opportunity to improve S/N is to consider noise distribution properties. It is often that the noise is not normally distributed (not Gaussian), and is overloaded with occasional spikes. In such situation, a Median filter shows better performance than a linear filter, such as PSoC5 Filter. Check if this custom community component is improving your S/N (no DMA needed)

MedianFilter: sliding window median filter component 

/odissey1

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Hi odissey1,

 

Thank you for your reply. I have tried your suggestion of the median filter and it looks to have helped on my benchtop setup here. I am going to send it out to do some further testing on the end hardware in the field. I will keep you posted on it.

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