convert raw reading from GPIO39 to voltage would result in crash

[erik2727]

<r>I could not understanding why ESP-IDF voltage calculation if apply to convert the raw reading from GPIO39 would result in crash
<br/>
uint32_t voltage = esp_adc_cal_raw_to_voltage(read_raw, adc_chars);<br/>
<br/>
Below is the simple source code<br/>
<br/>

Code: [Select all] [Expand/Collapse]

1. #include <stdio.h><br/>
2. #include <stdlib.h><br/>
3. #include "freertos/FreeRTOS.h"<br/>
4. #include "freertos/task.h"<br/>
5. #include "freertos/queue.h"<br/>
6. #include "driver/gpio.h"<br/>
7. #include "driver/adc.h"<br/>
8. #include "driver/dac.h"<br/>
9. #include "esp_system.h"<br/>
10. #include "esp_adc_cal.h"<br/>
11. #define BLINK_GPIO 2
12. <br/>
13. <br/>
14. static void Read_GPIO39() {<br/>
15.     int read_raw = 0;<br/>
16.     adc1_config_width(ADC_WIDTH_BIT_12);<br/>
17.     adc1_config_channel_atten(ADC1_CHANNEL_3, ADC_ATTEN_DB_11);<br/>
18.     read_raw=adc1_get_raw(ADC1_CHANNEL_3);<br/>
19.     **//uint32_t voltage = esp_adc_cal_raw_to_voltage(read_raw, adc_chars);**<br/>
20.     printf("Intensity : %d\n", read_raw);<br/>
21. <br/>
22.     //printf("Voltage: %d\n", voltage);<br/>
23.     gpio_pad_select_gpio(BLINK_GPIO);<br/>
24.     gpio_set_direction(BLINK_GPIO, GPIO_MODE_OUTPUT);<br/>
25.     gpio_set_level(BLINK_GPIO, 1);<br/>
26. }<br/>
27. <br/>
28. <br/>
29. void app_main() {<br/>
30.     ESP_ERROR_CHECK(nvs_flash_init());<br/>
31.     // initialise_wifi();<br/>
32.     while (1) {<br/>
33.         Read_GPIO39();<br/>
34. <br/>
35.         vTaskDelay(3000 / portTICK_PERIOD_MS);<br/>
36.         gpio_set_level(BLINK_GPIO, 0);<br/>
37. }<br/>
38. }

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What is adc_chars? How did you define it?

[erik2727]

with below statement , 7% variance is observed. I have doubt on the atten not sure should this be ADC_ATTEN_DB_11 or some others value for GPIO39 , voltage reading is very unstable on genuine espressif dev Wrover B development board


static const adc_atten_t atten = ADC_ATTEN_DB_11;
static const adc_unit_t unit = ADC_UNIT_1;
#define DEFAULT_VREF 1100
adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));

esp_adc_cal_characterize(unit, atten, ADC_WIDTH_BIT_12, DEFAULT_VREF,adc_chars);