A problem about MIMXRT1050 -EVK

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A problem about MIMXRT1050 -EVK

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1163164719
Contributor I

Now, I found a problem with the ADC acquisition of the RT1O5O. When I used the official ADC_ETC routine, I simulated it with Keli5 and found that the value obtained by ADC sampling has a large deviation, which is obviously inconsistent with the description in the data sheet. I set the weekly wave to collect 100 points, and then observe the collected points when the DC signal is sent to the GPIO_AD_B1_03 channel of the development board. When the value is binary, the first point is 1830, and the subsequent points will be larger. The float, the maximum value is 1848 and the minimum value is 1814. Such a deviation does not meet the accuracy requirements in the data sheet, so I would like to consult the sampling aspect of the ADC to achievepastedImage_1.jpg the accuracy requirements in the data sheet.

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kerryzhou
NXP TechSupport
NXP TechSupport

Hi ZhiJiang Wang,

   Thank you for your interest in NXP MIMXRT product, I would like to provide service for you.

  Please help to check these points at first:

1. Tell me the SDK sample code folder

  SDK_2.5.1_EVKB-IMXRT1050\boards\evkbimxrt1050\driver_examples\adc_etc

 Have two project, which project you are using?

2. Do you modify the SDK code?

  If yes, please tell me the detail points, or you can send me your test source code.

  Then I can test it on my side.

3. GPIO_AD_B1_03 pin, which detail test point you are testing on your MIMXRT1050-EVK board?

  Please double check your board, is it RT1050-EVK or RT1050-EVKB, EVK is the old board which my have bugs.

  EVKB is the new board.

4. what the DC voltage you are using?

   Where you get the DC voltage? Is it stable or not?

Waiting for your updated information, then I will help you to check the details.

Wish it helps you!

If you still have question about it, please kindly let me know.

Have a great day,
Kerry

 

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Contributor I

First of all, thank you for your reply, then I will answer your four points.
1, the source code of the program used is: SDK_2.5.1_EVKB-IMXRT1050 \ boards \ evkbimxrt1050 \ driver_examples \ adc_etc \ adc_etc_hardware_trigger_conv.

2, there is no general change to the source code, just use ADC1 and ADC2 at the same time, add an array and a pointer to observe the sampled value.

3. The test point is GPIO_AD_B1_03 at the upper left of the board, and the board used is the old board of EVK.

4. The number of DCs is divided by the 3.3V pin on the RT1050 and then applied to the GPIO_AD_B1_03 pin.

Finally, I heard that you said that EVK is the wrong old board, then we want to know what is wrong? Does the wrong place affect the function of the ADC?

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kerryzhou
NXP TechSupport
NXP TechSupport

Hi ZhiJiang Wang,

   Sorry for my later reply, there are a lot of cases in the queue need to do the testing.

   Today I test the SDK adc project on my side, when I connect the ADC pin to the ground, I can get the max data is 17.

   The ADC is used the 12 bit, so, when the VDDA is 3.3V, the LSB is just 3.3V/4096=0.805mv.

   Even you have about 1848-1814 fluctuate, it is just (1848-1814)*3.3V/4096=27.3mV, actually this voltage is not large, can't you receive this fluctuation?


Have a great day,
Kerry

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1163164719
Contributor I

HI,Kerry Zhou

I haven't received your reply for a long time, I want to ask about what else we need to provide. We are more interested in knowing how to achieve the accuracy in the data sheet. At least for now, the accuracy is only seven digits of precision, so we are wondering if our test methods are wrong and if we miss something.

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kerryzhou
NXP TechSupport
NXP TechSupport

Hi ZhiJiang Wang,

   Sorry for my later reply.

   Please check this application note about the SAR ADC measurements:

https://www.nxp.com/docs/en/application-note/AN4373.pdf 

  There are number of parameters can affect the ADC accuracy, please check more details from the application note.

  About the 3.4 LSB data in the datasheet, it also have the note:

1 All accuracy numbers assume the ADC is calibrated with VREFH=VDDAD
2 Typical values assume VDDAD = 3.0 V, Temp = 25°C, Fadck=20 MHz unless otherwise stated. Typical values are for reference only and are not tested in production.

 Please check the application note AN4373, it will more useful to get the correct ADC data.


Have a great day,
Kerry

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kerryzhou
NXP TechSupport
NXP TechSupport

Hi ZhiJiang,

   I will test the related ADC code on my new MIMXRT1050-EVKB board, and share the result with your later.

  Please give me more time, thank you!

Best Regards,

Kerry

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1163164719
Contributor I

Thank you very much, I am looking forward to your results.
During the test, I found that the power supply to the ADC is DCDC3.3V. I tried to change the power supply from DCDC3.3V to LDO3.3V. I found that the result is a little better than before, but the accuracy is still only 8 bits, far from satisfying ten. Two-digit precision.

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kerryzhou
NXP TechSupport
NXP TechSupport

Hi ZhiJiang Wang,

  Could you also share your LDO3.3v adc test result?


Have a great day,
Kerry

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Contributor I
Below is the result and code of the power supply I used to power the ADC with LDO3.3V. I can display the maximum and minimum values. It can be seen from the figure that the maximum and minimum difference is 30 points. I think this accuracy cannot be reached in the data sheet. The 3.4 points described. So I want to know what kind of environment can make the ADC reach the ten-digit precision in the data sheetIMG_20190603_103243.jpg.IMG_20190603_103301.jpg
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Contributor I

I hope that people who understand this issue can give me some advice.

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