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Interfacing stm32f1 with GSM

Bud
Associate III

I am trying to interface GSM with my ARM controller [stm32f103c8t6].

I knew a little about the working of GSM, 

- By sending the "AT" command to GSM, it will respond with a "OK" message.

Before interfacing GSM with arm, i learned how to use HAL_uart function (generated from cube MX). I tried to transmit and receive data to "arm and terminal(pc)" , and it works good in HAL_uart function.

Problem:

- But when i connect to GSM with ARM, No response is getting from GSM. 

- I tried another method, i use uart max232 with GSM to transmit and receive data it works fine. [sending data to pc terminal via max232].

I attached the uart communication diagram arm,gsm and max232.(I use max232 to communicate with pc since i have only st-link v2 which has no tx and rx).

Also the code generated from cube mx. 

0690X000006CSvSQAW.jpg

/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  ** This notice applies to any and all portions of this file
  * that are not between comment pairs USER CODE BEGIN and
  * USER CODE END. Other portions of this file, whether 
  * inserted by the user or by software development tools
  * are owned by their respective copyright owners.
  *
  * COPYRIGHT(c) 2018 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "stm32f1xx_hal.h"
 
/* USER CODE BEGIN Includes */
 
/* USER CODE END Includes */
 
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;
 
/* USER CODE BEGIN PV */
/* Private variables ---------------------------------------------------------*/
 
 
 
uint8_t atcmd[] = "AT\r\n";
uint8_t rx[10];
 
 
/* USER CODE END PV */
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_USART2_UART_Init(void);
 
/* USER CODE BEGIN PFP */
/* Private function prototypes -----------------------------------------------*/
 
/* USER CODE END PFP */
 
/* USER CODE BEGIN 0 */
 
/* USER CODE END 0 */
 
/**
  * @brief  The application entry point.
  *
  * @retval None
  */
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_USART1_UART_Init();
  MX_USART2_UART_Init();
  /* USER CODE BEGIN 2 */
 
  /* USER CODE END 2 */
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
 
 // uart1 = GSM 				 and   stm32f1**
 // uart2 = terminal(pc) and   stm32f1**
 
HAL_UART_Transmit(&huart1,atcmd,10,10);        // transmitting "AT" commands to uart1(GSM)
		HAL_Delay(200);
HAL_UART_Receive(&huart1,rx,10,10);            // Receiveing the response for the AT cmd as "OK"
		HAL_Delay(200);
		
HAL_UART_Transmit(&huart2,rx,10,10);		       // Transmitting the revceived data of gsm to the terminal
  }
 
 
}
 
/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
 
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
 
    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = 16;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
    /**Initializes the CPU, AHB and APB busses clocks 
    */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
    /**Configure the Systick interrupt time 
    */
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
 
    /**Configure the Systick 
    */
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
 
  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
 
/* USART1 init function */
static void MX_USART1_UART_Init(void)
{
 
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
}
 
/* USART2 init function */
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(__FILE__, __LINE__);
  }
 
}
 
/** Configure pins as 
        * Analog 
        * Input 
        * Output
        * EVENT_OUT
        * EXTI
*/
static void MX_GPIO_Init(void)
{
 
  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
 
}
 
/* USER CODE BEGIN 4 */
 
/* USER CODE END 4 */
 
/**
  * @brief  This function is executed in case of error occurrence.
  * @param  file: The file name as string.
  * @param  line: The line in file as a number.
  * @retval None
  */
void _Error_Handler(char *file, int line)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  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,
     tex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
 
/**
  * @}
  */
 
/**
  * @}
  */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

1 REPLY 1

I don't think synchronous polling approach is OK for this type of application (especially when you don't know how much data you gonna get on rx), but obviously you are a novice in microcontroller programming, so let's try to solve your current problems first.

> HAL_UART_Transmit(&huart1,atcmd,10,10);

Why 10, 10? Your AT\r\n command is 4 bytes long. 10ms is OK for sending 4 bytes, so the second 10 is OK, but the first one should be 4 (you are currently sending 6 more "garbage" bytes to the modem).

> HAL_Delay(200);

> HAL_UART_Receive(&huart1,rx,10,10);

Again, why 10, 10? Also, while you are delaying 200ms the answer is already sent by the modem, so when you try to receive the data it's already late. Delete the delay, use longer timeout for receiving if 10ms is too little.