LPADC Interrupt - Reading Constant 4095

Hello All,

I am currently trying to implement an LPADC interrupt-driven application on the MAAXBOARD RT. To get started. Specifically, I am attempting to read analog values from the following GPIO pins:

GPIO_AD_13
GPIO_AD_19
GPIO_AD_15

However, when I read the ADC values from these pins, I consistently receive a value of 4095. This occurs across all three pins.

Could you please provide some insight into what might be causing this issue? I suspect there might be a configuration problem or a misunderstanding on my part regarding the hardware or software setup for these specific GPIO pins on the MIMXRT1176DVMAA within the MAAXBOARD RT context.

Any guidance or suggestions on how to troubleshoot this constant reading of 4095 would be greatly appreciated. I am available to provide further details about my setup or the modifications I have made to the example code if needed.

Thank you for your time and assistance.

Regards,

Sanjana S

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0 dougw 4 months ago

Is there a pull-up resistor enabled on the input?
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0 dougw 4 months ago

Is there a pull-up resistor enabled on the input?
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0 TheSanjanaSuresh 4 months ago in reply to dougw
No, this is my configuration for GPIO_AD_16 (note: GPIO_AD_15 does not exist on this device):

IOMUXC_SetPinConfig(

IOMUXC_GPIO_AD_16_GPIO_MUX3_IO15,

0x02U);

This configuration, based on the default provided by the SDK examples, has a changed register value and is working correctly.

However, I am encountering an issue with the reference voltage for the ADC. I am consistently getting 1.89V, but I need to set it to 3.3V.

According to the datasheet of MIMXRT1176DVMAA:

$V DD A_A D C_1 P 8 : 1.65 V t o 1.95 V$

$V DD A_A D C_3 P 3 : 3.0 V t o 3.6 V$

$A D C_V REF H : 1.0 V t o 1.89 V$

It seems that when I use kLPADC_ReferenceVoltageAlt1, it correctly selects $A D C_V REF H$ , resulting in the 1.89V reading. How can I configure the ADC to use a 3.3V reference voltage (likely $V DD A_A D C_3 P 3$ )? I am getting 1.89V maxx even when I try other reference voltage configurations.

Note: Remaing

GPIO_AD_13

GPIO_AD_19 still I'm getting 4095 reanding
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0 michaelkellett 4 months ago in reply to TheSanjanaSuresh

I had a quick look at the reference manual and the data sheet for the processor and found them to be very unclear. I think it is possible that the use of a Vref = 3.3V is not supported.

Unfortunately the reference manual refers to Vssa which is not to be found in the data sheet.

I think you will need to ask NXP tech support

MK
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0 TheSanjanaSuresh 4 months ago in reply to michaelkellett

Ok. Thank You!
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0 TheSanjanaSuresh 4 months ago in reply to dougw

Sorry, I forgot to modify channel B in the configuration.
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