RT1020 ADC issues

[joshgentrycargt]

The design I'm using is using ADC2 channel 3. This ADC pin does not work correctly. To double check if there was a design issue, when this pin is used on the MIMXRT1020-EVK it still does not work. R249 and R251 are removed so that it is not connected to a pull up. The behavior I see is it appears to be pulled up and increases up to and stays at a value of ~2700. A square wave running at 1khz from an oscilloscope is put onto the header at J19 pin 10. This input is used on J18 pin 1 when using channel 10.

I used the evkmimxrt1020_adc_12b1msps_sar_interrupt example from the sdk as it most closely represents the settings I'm using in my design. 

This is the config I used with the sdk:

#define DEMO_ADC_BASE ADC2

#define DEMO_ADC_IRQn ADC2_IRQn

#define DEMO_ADC_USER_CHANNEL 3U

#define DEMO_ADC_CHANNEL_GROUP 0U

#define EXAMPLE_ADC_IRQHandler ADC2_IRQHandler

Pin configuration with the pins tool for [90] GPIO_AD_B1_02:

Peripheral: ADC2

Signal: IN, 3

Slew Rate: Slow

Software Input On: Disabled

Open Drain: Disabled

Speed: Medium

Drive Strength: RO/6

Pull/Keeper select: Keeper

Pull/Keeper enable: Disabled

Pull Up/Down Config: 100k Ohm Pull Down

Hysteresis: Disable

Using [90] GPIO_AD_B1_10 with the same configuration above,

but for signal IN, 10 works. The only change in software is made to:

DEMO_ADC_USER_CHANNEL 10U

Both pins are enabled for the test but only one is used at a time.

I tried many settings to get some sort of response from the pin, but

it never returns a reasonable value.

In ADC_Init, I added this above "base->CFG = tmp32;" and tested all

of the values for the averaging:

// kADC_HardwareAverageCount4 = 0U, /*!< For hardware average with 4 samples. */

// kADC_HardwareAverageCount8 = 1U, /*!< For hardware average with 8 samples. */

// kADC_HardwareAverageCount16 = 2U, /*!< For hardware average with 16 samples. */

// kADC_HardwareAverageCount32 = 3U, /*!< For hardware average with 32 samples. */

// kADC_HardwareAverageDiasable = 4U, /*!< Disable the hardware average function. */

tmp32 |= ADC_CFG_AVGS(kADC_HardwareAverageCount8);

base->CFG = tmp32;

I did this with and without enabling averaging to try and find

one working setting:

tmp32 |= ADC_GC_AVGE_MASK;

base->GC = tmp32;

I'm looking for a way to get this pin working and would appreciate any help!

MCUXPresso 11.9.0

SDK 2.15.0

Problem occurs with the MIMXRT1020-EVK board as well as the MIMXRT1021DAG5A chip in the design.

[joshgentrycargt]

I made your changes to this project and still see the same results. Attached is my workspace. I also attached a version of adc_interrupt.c that fills a buffer instead of using getchar. I'm using a mag wire connected to J19 pin 10 to drive ADC2 channel 3.

[mayliu1 · Accepted solution]

Hi @joshgentrycargt ,

Thank you for your updated information.

I down load your project, and add print information, ADC2 channel3 work normal.

ADC2 channel3 connect AREF.

ADC2 channel3 connect GND.

Please be aware that ADC2 channel3 PIN is PIN90（GPIO_AD_B1_02）, This pin is not connect to  J19 pin 10(GPIO_SD_B1_02). 

I connect one end of resistor R85(Connect PIN90) with a wire harness, and the other end to GND or AREF.

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

Best Regards

mayliu

[joshgentrycargt]

Got the SD mixed up with the AD signal bank. Thanks!

[mayliu1]

Hi  ,

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

I used the MIMXRT1020-EVK board to verify ADC1 channel 0 and ADC2 channel 3, and the ADC conversion results are normal without any issues.

1：Please open the Pins  Tool, and Set ADC2 channel3, and click Update Code button.

2:  In the Project " evkmimxrt1020_adc_12b1msps_sar_interrupt"

Please add code as what I do.

The image below shows the results of my validation.

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

Best Regards

mayliu