類比輸入(ADC)

Analog Inputs (ADC)

Reading an analog value with the ESP32 means you can measure varying voltage levels between 0 V and 3.3 V.
12-bit resolution. This means that when you read an analog input, its range may vary from 0 to 4095.
Non-linear
- ESP32 is not able to distinguish 3.3 V from 3.2 V. You'll get the same value for both voltages: 4095.
- ESP32 is not able to distinguish 0 V from 0.13 V. You'll get the same value: 0.

支援 GPIO

ESP32 supports measurements in 18 different channels

ADC1_CH0 (GPIO 36)
ADC1_CH1 (GPIO 37)
ADC1_CH2 (GPIO 38)
ADC1_CH3 (GPIO 39)
ADC1_CH4 (GPIO 32)
ADC1_CH5 (GPIO 33)
ADC1_CH6 (GPIO 34)
ADC1_CH7 (GPIO 35)
ADC2_CH0 (GPIO 4)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH1 (GPIO 0)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH2 (GPIO 2)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH3 (GPIO 15)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH4 (GPIO 13)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH5 (GPIO 12)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH6 (GPIO 14)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH7 (GPIO 27)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH8 (GPIO 25)：ADC2 pins cannot be used when Wi-Fi is used
ADC2_CH9 (GPIO 26)：ADC2 pins cannot be used when Wi-Fi is used

https://www.espboards.dev/esp32/nodemcu-32s/

一、光敏電阻

光敏電阻

光敏電阻模組

EXP1 光敏電阻控制

1.1 電路

1.2 實作

1.2.1 積木程式

開瀏覽器，連線

http://easycoding.tn/esp32/demos/code/

完成之積木程式

1.3 DEMO

Arduino IDE 開啟載入程式碼(.ino)，選擇正確控制板，選擇正確連接埠，上傳燒錄。開啟序列埠視窗，baudrate 9600

1.4 語法

setup()

analogReadResolution(resolution); // 設定解析度, 數值：9(0 – 511)~12(0 – 4095), 預設：12 bits(0 – 4095)

...

analogSetWidth(width); // 設定解析度, 數值：9(0 – 511)~12(0 – 4095), 預設：12 bits(0 – 4095)

...

analogSetCycles(cycles); // set the number of cycles per sample. Default is 8. Range: 1 to 255.

...

analogSetSamples(samples); // set the number of samples in the range. Default is 1 sample. It has an effect of increasing sensitivity.

...

analogSetClockDiv(attenuation); // set the divider for the ADC clock. Default is 1. Range: 1 to 255.

...

analogSetAttenuation(attenuation); // sets the input attenuation for all ADC pins. Default is ADC_11db. Accepted values:

ADC_0db: sets no attenuation. ADC can measure up to approximately 800 mV (1V input = ADC reading of 1088).
ADC_2_5db: The input voltage of ADC will be attenuated, extending the range of measurement to up to approx. 1100 mV. (1V input = ADC reading of 3722).
ADC_6db: The input voltage of ADC will be attenuated, extending the range of measurement to up to approx. 1350 mV. (1V input = ADC reading of 3033).
ADC_11db: The input voltage of ADC will be attenuated, extending the range of measurement to up to approx. 2600 mV. (1V input = ADC reading of 1575).

...

analogSetPinAttenuation(pin, attenuation); // sets the input attenuation for the specified pin. The default is ADC_11db. Attenuation values are the same from previous function.

...

adcAttachPin(pin); // Attach a pin to ADC (also clears any other analog mode that could be on). Returns TRUE or FALSE result.

...

adcStart(pin);, adcBusy(pin); and resultadcEnd(pin); // starts an ADC convertion on attached pin’s bus. Check if conversion on the pin’s ADC bus is currently running (returns TRUE or FALSE). Get the result of the conversion: returns 16-bit integer.