# STM32 - ADC
###### tags: `firmware_hardware` `electrical_system` `NTURT`

#### Author: @andre-liang


source: [link](https://open.spotify.com/playlist/37i9dQZF1DZ06evO49hLQA)

### Preface

ADC (Analog-to-Digital Converter) is a peripheral to measure analog signal.

### How it works?


source: [link](https://www.mlmvlab.bime.ntu.edu.tw/_files/ugd/0752bb_b825987585d6457998471ca802a351c0.pdf)

There many way to design a ADC, one of which is successive approximation ADC. It essencially use different sample voltage to sample the unknown outside voltage. Due to the sampling process, the our ADC has a smaple rate, which decide how fast the MCU can convert the analog signal to digital signal. Also as the resolution increase, the ADC's conversion speed becomes slower.

### Config

#### Channel


One ADC unit can have multiple channel, enable the MCU to measure multiple analog signals at once.

Each ADC can also operate in regular mode or injected mode. In regular mode, the ADC convert each channel one after another. While in injected mode, the ADC will prioritize the convertion of injected group channel, achieving lower latency.

#### DualMode

On our STM32, there are two ADCs, which we can synchronize together to get more accurate results.

#### Get your values

Just like other STM32 peripherals, the ADC can be driven in three modes: polling, interrupt and DMA (Direct Memory Access) mode.

#### Setup


Generate a new project using STM32CubeMX, Enable `ADC1->Temperature Sensor Channel`.

*Note that if you want to read multiple channel, it is recommended to use the DMA mode & injected group channel and is generally more complicated.*

### Example

In this example, we will measure the temperature of the chip by using internal temperature channel and ADC.

For simplicity, we will use pooling to get the ADC conversion value.

### Variables

float temperture;

Declare the `temperture` variable in global variable so that it could be displayed on the live expression window.

### Functions


source: [link](https://www.st.com/en/microcontrollers-microprocessors/stm32g431kb.html#st_all-features_sec-nav-tab)

So we can get the relation:

$$ V=V_{30}+ \textrm{Avg_Slope} \times \left( T-30 \right) $$

$$ T= \frac{ \left(V-V_{30}\right)}{\textrm{Avg_Slope}} $$

By using the sensor characteristics, we can get the current temperature by reading the voltage output of the sensor.

First start the ADC before the main loop,
then read the value of ADC in pooling mode, finally convert the voltage into temperture.

/* USER CODE BEGIN 2 */

	HAL_ADC_Start(&hadc1);

	/* USER CODE END 2 */

	/* Infinite loop */
	/* USER CODE BEGIN WHILE */
	while (1) {
		/* USER CODE END WHILE */
		HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
		adc_value = HAL_ADC_GetValue(&hadc1);
		voltage = (double) adc_value / 4095.0 * 3.3;
		temperture = (voltage - 0.76) / (0.0025);
		HAL_Delay(200);
		/* USER CODE BEGIN 3 */
	}
	/* USER CODE END 3 */

But since our sensor is not calibrated, we don't expect you to get accurate results. :disappointed_relieved:

### Conclusion

The ADCs (Analog-to-Digital Converters) offer a robust mechanism for your microcontroller to capture analog signals from the external environment. It's important to recognize that analog signals are susceptible to interference. Therefore, in order to secure accurate readings, it's advisable to calibrate your sensor or employ statistical techniques to effectively reduce signal noise. This meticulous approach ensures the reliability of the obtained results despite the inherent challenges posed by analog signals.