ESP32 DevKit C V4 - ADC - Pull Up?

[Ronnie Eriksson]

Hi everyone,

I'm haveing this issue - My ADC inputs seems to have a pullup at ADC inputs at my ESP32 DevKit C V4 and I'd like the them float.

I've tested ADC1_0 and ADC2_6 both inputs gives me a currentreading of 0.5 mA with a DMM set to a range of 2mA. Measuring the voltage I get 3.7 VDC. I've searched internet and it seems like this is what many users would like. Me I'm thinking of connecting a relatively high impedance sorce to the ADC input, and there fore a floating input would be aprciated.

I've used the folowing code:

Pin setup:

Code: [Select all] [Expand/Collapse]

1. #define PHOTO_ADC_INPUT 14

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Code: [Select all] [Expand/Collapse]

1.     gpio_reset_pin(PHOTO_ADC_INPUT);
2.     gpio_set_direction(PHOTO_ADC_INPUT, GPIO_MODE_INPUT);  
3.     gpio_set_direction(PHOTO_ADC_INPUT, GPIO_FLOATING);

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ADC setup:

Code: [Select all] [Expand/Collapse]

1.     //-------------ADC1 Init---------------//
2.     adc_oneshot_unit_handle_t adc2_handle;
3.     adc_oneshot_unit_init_cfg_t init_config2 = {
4.         .unit_id = ADC_UNIT_2,
5.         .ulp_mode = ADC_ULP_MODE_DISABLE,
6.     };  
7.     ESP_ERROR_CHECK(adc_oneshot_new_unit(&init_config2, &adc2_handle));
8.  
9.     //-------------ADC1 Config---------------//
10.     adc_oneshot_chan_cfg_t config = {
11.         .bitwidth = ADC_BITWIDTH_DEFAULT,
12.         .atten = ADC_ATTEN_DB_11,
13.     };
14.     ESP_ERROR_CHECK(adc_oneshot_config_channel(adc2_handle, ADC_CHANNEL_6, &config));

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Reading ADC:

Code: [Select all] [Expand/Collapse]

1.     static int ADC_Reading;
2.     ESP_ERROR_CHECK(adc_oneshot_read(adc2_handle, ADC_CHANNEL_6, &ADC_Reading));

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Can some one please help me get the inputs float?