Capacitive Soil Moisture Module Project With STM32F303 Microcontroller Series

September 24, 2024

Capacitive Soil Moisture Module Project With STM32F303 Microcontroller Series

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September 24, 2024

Capacitive Soil Moisture Module Project With STM32F303 Microcontroller Series

What's the purpose of this project?

In this section, we are going to launch the Capacitive Soil Moisture Module using an ARM microcontroller, STM32F series. To use more conveniently and optimally in this project, we use two ready modules GB632EN and GebraBit STM32F303. These two modules contain the minimum necessary elements of the Capacitive Soil Moisture Sensor and the STM32F microcontroller, which are provided by the GebraBit team to facilitate the work.

What are we going to learn in this tutorial?

In this tutorial, in addition to setting up and using the Soil Moisture module, you will get to know how to set the various parts of the STM32 microcontroller to set up this sensor using the ADC, how to use the GB632EN module specific library and driver file. You will also learn how to declare functions and finally receive sensor data in the Keil compiler.

What do we need to start this project?

As you probably know, we need some hardware and software to do this project. The titles of these hardware and software are provided to you in the table below and you can prepare/download them by clicking on each of them and get ready to start.

Required hardware	Required software
GebraBit Capacitive Soil Moisture	Keil compiler
GebraBit STM32F303 module	STM32CubeMX program
ST-LINK/V2 programmer

irst as shown in the image below, we connect the GebraBit Capacitive Soil Moisture module to the GebraBit STM32F303 module as follows:

Note: Set the VCC SEL jumper to 3v3 otherwise you may damage the microcontroller pins.
Finally, we will see the value of the Soil Moisture in Real Time in the “Watch1” window of the Keil compiler in the “Debug Session” mode.
Note: To have more accurate data calibrate the module as mentioned below.

STM32CubeMX settings

In the following, we review the settings related to each of the “ADC”, “RCC”, “Debug”, ”GPIO” and “Clock” sections in the STM32F303 microcontroller to develop the GebraBit Soil Moisture module.

RCC settings

Due to the presence of “8Mhz” crystal in the GebraBit STM32F303 module, we select the “external clock” in the “RCC” section:

Debug & Programming settings

Regarding the access to “SWCLK” and “SWDIO” pins in the GebraBit STM32F303 module, to reduce the number of pins during “Debug & Programming”, in the “SYS” block, we select the “Serial Wire” option in the “Debug” section:

ADC settings

To get the Soil Moisture module output voltage with the GebraBit STM32F303 module enable the ADC in single-ended mode and select PA0 as ADC1_IN1:

GPIO settings

The Gebrabit STM32F303 module has built-in LED and pushbutton in PB6 and PA3 pins so we make the PB6 pin as GPIO_OUTPUT and PA3 pin as GPIO_INPUT to make the cube setting more functional and let you make your ideas into reality with these two modules.

Clock settings

The “clock” settings for each part of the STM32F303 microcontroller in this code, are as follows:

Project Manager settings

“Project Manager” settings are as follows, here we have used “MDK-ARM” version “5.32” compiler:

here we have used the “MDK-ARM” version “5.32” compiler:

After completing all the above settings, we can develop our code easily just by one click on “GENERATE CODE” and adding the SoilMoisture library and driver (provided by GebraBit).
You can download the “STM32Cube MX”, “library”, “driver” and KEIL project at the end of this tutorial.

Capacitive Soil Moisture library and driver

In addition to the modular design of various sensors and ICs, GebraBit tries to provide a variety of structured and hardware-independent libraries in C language for the ease of users in setting up and developing software.
For this purpose, after preparing each GebraBit module, the users can refer to the “tutorial” section of the desired module and download the dedicated library, which contains the “ .h” and “ .c” files (Header and Source) and a sample training program under “GebraBit STM32F303”, “GebraBit ATMEGA32A” or “Arduino” development boards.
All the defined functions and structures in the library are commented in full detail and all the received parameters in the arguments of the functions and their return values, are briefly explained. Since the libraries are hardware-independent, the user can easily add the library in any of their favorite compilers and develop it by the desired microcontroller and development board.

GebraBit_Capacitive_Soil_Moisture.h header file

In this file the casing of the module and the configurations related to each of the module’s internal blocks are defined in the form of a “STRUCT” with the name GebraBit_SoilMoisture Finally, in the Debug Session environment, all the configurations related to each block can be seen in real time.

SoilMoisture struct

All sensor properties and sensor data are defined in this “struct” and all the information and configuration implemented on the sensor are stored in this “structure” and you can see the changes in each part of the sensor in the “Debug Session” environment.

				
					typedef struct SoilMoisture
{
            uint8_t                            SOIL_MOISTURE_PERCENTAGE;
            char *                             SOIL_MOISTURE_STATUS;
            uint32_t                           ADC_VALUE_IN_AIR;
            uint32_t                           ADC_VALUE_IN_WATER;
            uint32_t                           ADC_RAW_VALUE;
            float                              ADC_INPUT_VOLTAGE_VALUE;
            ADC_HandleTypeDef                  ADC_HANDELER;
}GebraBit_SoilMoisture;

Declaration of functions

At the end of this file, all the functions for receiving data from the module and calibration are declared:

				
					void GB_SoilMoisture_Configuration(GebraBit_SoilMoisture * SoilMoisture);
void GB_SoilMoisture_Calibration(GebraBit_SoilMoisture * SoilMoisture, uint32_t AirADCValue, uint32_t WaterADCValue);
void GB_SoilMoisture_Read_ADC_Value(GebraBit_SoilMoisture * SoilMoisture);
void GB_SoilMoisture_Calculate_SoilMoisture_Percentage(GebraBit_SoilMoisture * SoilMoisture);
void GB_SoilMoisture_Get_Data(GebraBit_SoilMoisture * SoilMoisture);

GebraBit_Capacitive_Soil_Moisture.c source file

In this file, which is written in C language, all the functions are commented on in full detail, and all the parameters received in the arguments of the functions and their return values are clearly explained so we confine to these explanations and invite users to check this file directly for more information.

Sample program in Keil

After making the Keil project by STM32CubeMX and adding the “GebraBit_SoilMoisture.c” library provided by GebraBit, we will examine the “main .c” file of the sample tutorial and view the output of the GebraBit_SoilMoisture module in the “watch” part in the Keil compiler “Debugging” environment.

Description of “main.c” file

functions required by the GebraBit SoilMoisture module have been added to the structures. In the next part, a variable named SoilMoisture_Module of the GebraBit_SoilMoisture structure type (this structure is in the GebraBit_SoilMoisture header and is explained in the GebraBit_SoilMoisture library description section) is defined for the configuration of the GebraBit SoilMoisture module:

				
					/* USER CODE BEGIN PTD */
GebraBit_SoilMoisture SoilMoisture_Module;
/* USER CODE END PTD */

In the next part of the written code, using the GB_SoilMoisture_Configuration (&SoilMoisture_Module) function and GB_SoilMoisture_Calibration (&SoilMoisture_Module,Module ADC Value in air, Module ADC Value in water) , we set the GebraBit SoilMoisture module and finally, in the while part of the program, the data is read from the sensor and Digital Status and ADC values are continuously received:

				
					  /* USER CODE BEGIN 2 */
  GB_SoilMoisture_Configuration(&SoilMoisture_Module);
  GB_SoilMoisture_Calibration(&SoilMoisture_Module,2080,1040);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */   
    GB_SoilMoisture_Get_Data(&SoilMoisture_Module); 
    HAL_Delay(500);
  }
  /* USER CODE END 3 */

Note: to calibrate the module and have more accurate data you set values for two parameters of the calibration function, the first one is AirADCValue(this value in sample code is 2080) and the second one is WaterADCValue(this value in sample code is 1040).
to find these values you need a glass of water, first, compile the program and then open the Debug session and run it, add the SoilMoisture_Module to the watch and you can see the live ADC value in ADC_RAW_VALUE, measure and write down this value when module surface is completely dry and when the module is placed in a cup of water, then place the first one in AirADCValue parameter of the calibration function and the second one in WaterADCValue parameter.
Caution: the module is not waterproof and avoid getting the electrical components wet.

The “main.c” file code text:

				
					/* USER CODE BEGIN Header */ 
/* 
 * 
_________________________________________________________________________________
 _______________________ 
 * Copyright (c) 2020 GebraBit Inc. All rights reserved. 
 * 
 * This software, related documentation and any modifications thereto 
(collectively �Software�) is subject 
 * to GebraBit and its licensors' intellectual property rights under U.S. and 
international copyright 
 * and other intellectual property rights laws.  
 * 
 * GebraBit and its licensors retain all intellectual property and proprietary 
rights in and to the Software 
 * and any use, reproduction, disclosure or distribution of the Software without 
an express license agreement 
 * from GebraBit is strictly prohibited. 
  
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT  
 * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
PURPOSE AND NON-INFRINGEMENT IN   
 * NO EVENT SHALL GebraBit BE LIABLE FOR ANY DIRECT, SPECIAL, INDIRECT, 
INCIDENTAL, OR CONSEQUENTIAL DAMAGES,  
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER 
IN AN ACTION OF CONTRACT, 
 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE 
USE OR PERFORMANCE 
 * OF THE SOFTWARE. 
 * 
_________________________________________________________________________________
 _______________________ 
 */ 
/** 
  ****************************************************************************** 
  * @file           : main.c 
  * @brief          : Main program body 
  * @Author         : Sepehr Azimi 
  ****************************************************************************** 
  * @attention 
  * 
  * Copyright (c) 2022 STMicroelectronics. 
  * All rights reserved. 
  * 
  * This software is licensed under terms that can be found in the LICENSE file 
  * in the root directory of this software component. 
  * If no LICENSE file comes with this software, it is provided AS-IS. 
  * 
  ****************************************************************************** 
  */ 
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "adc.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "GebraBit_Capacitive_Soil_Moisture.h"
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
GebraBit_SoilMoisture SoilMoisture_Module;
/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ADC1_Init();
  /* USER CODE BEGIN 2 */
  GB_SoilMoisture_Configuration(&SoilMoisture_Module);
  GB_SoilMoisture_Calibration(&SoilMoisture_Module,2080,1040);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */   
    GB_SoilMoisture_Get_Data(&SoilMoisture_Module); 
    HAL_Delay(500);
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_ADC12;
  PeriphClkInit.Adc12ClockSelection = RCC_ADC12PLLCLK_DIV1;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

Program output

After generating the Keil project using STM32CubeMX and adding the library, we connect the STLINK V2 programmer to the GebraBit STM32F303 using the STLINKV2 adapter:

STLINKV2 adapter:

By connecting the STLINK V2 programmer to the GebraBit STM32F303, there is no need to apply power to the GebraBit STM32F303 and GebraBit SoilMoisture modules, because they receive their supply voltage directly from the STLINK V2 programmer.
Finally, enter the “Debug” mode and by adding the “SoilMoisture_Module” to the “watch” window and running the program, we can see the changes in the RH and Status values of the GebraBit SoilMoisture module:

In the following, you can download the “GebraBit SHT35 module setup project” using the GebraBit STM32F303 module in the Keil environment, the “STM32CubeMX file”, the schematic of the modules and the “SHT35 datasheet”.