29. ADC Serial plotter

Key Peripherals Used

• ADC1 Channel 0 (PA0): Reads the analog voltage from the potentiometer.
• USART2: For serial communication with a serial terminal to display voltage.

STM32 Hardware Connection

• Potentiometer connection:
  • Connect the potentiometer’s middle pin (wiper) to PA0 (ADC1_IN0) for analog input.
  • Connect the two outer pins of the potentiometer to 3.3V (VCC) and GND to form a voltage divider.
  • Use a 10 kΩ potentiometer for best results.
• Use USART2 on the STM32 board for serial communication via the USB interface to transmit the measured analog values to a serial plotter.

Circuit Diagram

STM32 Firmware Implementation

Project Setup in STM32CubeIDE

1. Create a Project
   • Open STM32CubeIDE, start a new project, and select the NUCLEO-F103RB board.
2. Basic Configuration (via CubeMX inside CubeIDE)
   • Clock: Use the default HSI oscillator with PLL enabled (as configured in SystemClock_Config).
   • GPIO: Enable clocks for PORTA, PORTB, PORTC, and PORTD.
   • ADC1 (Analog Input Source)
     • Resolution: 12-bit (0–4095 range).
     • Conversion mode: Single, software-triggered.
     • Channel: ADC_CHANNEL_0 (PA0).
   • USART2: Enabled at 115200 baud, 8-N-1.
3. Code Generation
   • CubeMX will automatically generate all the startup code, including:
     • HAL_Init() → Initializes HAL and system tick.
     • SystemClock_Config() → Configures system clock (HSI + PLL).
     • MX_GPIO_Init() → Initializes GPIO ports.
     • MX_USART2_UART_Init() → Configures UART2.
     • MX_ADC1_Init() → Configures ADC1 for analog input.
   • This code sets up the hardware and prepares the project for firmware development, so we only need to add our application logic in the user code sections

Code Snippets from main.c

ADC Initialization (MX_ADC1_Init):

static void MX_ADC1_Init(void)
{
  ADC_ChannelConfTypeDef sConfig = {0};

  /** Common config
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_13CYCLES_5;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }

}

This configures ADC1 for single-channel operation with right-aligned 12-bit results.

UART2 Initialization (MX_USART2_UART_Init):

static void MX_USART2_UART_Init(void)
{
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
}

This configures USART2 for communication at a 115200 baud rate with 8 data bits, no parity, and 1 stop bit, supporting both transmit and receive.

Header includes:

#include<string.h>

#include<stdio.h>

Private Variables:

// Buffer to hold ADC value string
char buff[10];

Main Loop - Reading and Transmitting ADC Values

while (1) {
  // Start ADC conversion
  HAL_ADC_Start(&hadc1);

  // Wait for ADC conversion to complete
  HAL_ADC_PollForConversion(&hadc1, 20);

  // Read the converted ADC value (12-bit resolution)
  uint16_t adcValue = HAL_ADC_GetValue(&hadc1);

  //convert integer value into string
  sprintf(buff, "%d\n", adcValue);

  //Transmit string on UART
  HAL_UART_Transmit(&huart2, (uint8_t*)buff, strlen(buff),
                    HAL_MAX_DELAY);

  HAL_Delay(500);
}

Main Loop Workflow

• HAL_ADC_Start() initiates ADC conversion.
• HAL_ADC_PollForConversion() waits until the conversion completes.
• HAL_ADC_GetValue() reads the 12-bit result.
• sprintf() formats the value as a string.
• HAL_UART_Transmit() sends the data to the serial monitor.

Download Project

The complete STM32CubeIDE project (including .ioc configuration, main.c, and HAL files) is available here:

📥 Download Project

ESP32 Circuit Connection 

• Interface Potentiometer with GPIO pin 34.

ESP32 Firmware Implementation

Let us write the code for this ADC serial plotter setup. It is very straightforward :

• Read the analog value
• Transmit it to the Serial plotter
• The serial plotter will plot these values

Code

//Hardware configuration
#define POT_PIN 15

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);  // Set ADC resolution to 12-bit (default)
}

void loop() {
  // Read the analog values from pin 15
  int analogValue = analogRead(POT_PIN);

  // For the Serial Plotter, just print the values without any text
  Serial.println(analogValue);
  delay(100);  // Add a short delay to control the update rate
}

Code Explanation

• analogRead(analogPin):  reads  ADC value.
• Serial.println:  print ADC_value on the Serial monitor.

Arduino UNO Circuit connection

Arduino UNO Firmware Implementation

Let us write the code for this ADC serial plotter setup. It is very straightforward :

• Read the analog value
• Transmit it to the Serial plotter
• The serial plotter will plot these values

Code

void setup() {
  Serial.begin(9600);
}

void loop() {
  // Read the analog values from A0
  int analogValueA0 = analogRead(A0);

  // For the Serial Plotter, just print the values without any text
  Serial.println(analogValueA0);
  delay(100);  // Add a short delay to control the update rate
}

Code explanation

• analogRead(analogPin):  reads  ADC value.
• Serial.println:  print ADC_value on Serial monitor.

Output

The circuit is easy. Shown below

The output of increasing value is as above

Output video