Not Getting sim800 response correctly - stm32

Question

I am struggling to get correct response (OK) from sim800L module that is connected with stm32f103. But through serial terminal (using USB to serial module) everything(sms, call,gprs) is working fine.
I am getting series of AAAAAAA........ . I tried it with echo off but same response
Reduced the timeout too.
here is my piece of code
#include "main.h"
#include "stdio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "string.h"
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
unsigned char E[]={10},G[]={34},S[]={26},C[]={13};
#define SUB HAL_UART_Transmit(&huart1,(unsigned char*)S,1,1000);
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart3;
/* USER CODE BEGIN PV */
unsigned char tx_buffer[50],rx_buffer[50]={'\0'};
uint8_t x=26;
char send_str[33]={'\0'};
char Num_str[11]={"xxxxxxxxxx"};
char sending_sms_str[65] = {'\0'};
unsigned char msg_str[50]="good morning shubham";
/* 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_USART3_UART_Init(void);
/* USER CODE BEGIN PFP */
void sim800_init(void);
void sim800_call(void);
void sim800_sms(void);
void sim800_gprs(void);
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/*
void sim800_response(void)
{
char response[200];
for(int i = 0 ; i<200 ; i++)
{
response[i++] = HAL_UART_Receive(&huart1,(unsigned char *)rx_buffer,1,100);
}
HAL_Delay(200);
HAL_UART_Transmit(&huart3,(unsigned char *)response,strlen(response),100);
}
*/
void sim800_test(void)
{
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r",strlen("AT\r"),100);
HAL_Delay(300);
//HAL_UART_Transmit(&huart1,(uint8_t *) "AT+IPR=9600\\n" , strlen ("AT+IPR=9600\r\n"),100);
//HAL_Delay(200);
HAL_UART_Receive(&huart3,(uint8_t *)rx_buffer,sizeof(rx_buffer),100);
HAL_Delay(200);
//sim800_response();
HAL_UART_Transmit(&huart1,(uint8_t *)rx_buffer,sizeof(rx_buffer),100);// to Uart1 for debugging the response
HAL_Delay(200);
rx_buffer[0] = '\0';
}
void sim800_init(void)
{
HAL_Delay(10000);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r\n",strlen("AT\r\n"),1000);
HAL_Delay(500);
//-----------------------------
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+IPR=9600\r\n",strlen("AT+IPR=9600\r\n"),1000);
HAL_Delay(500);
}
void sim800_call(void) // working
{
char rxbuf[50];
HAL_UART_Transmit(&huart3,(uint8_t *)"ATD xxxxxxxxxx;\r\n",strlen("ATD xxxxxxxxxx;\r\n"),1000);
HAL_Delay(100);
HAL_UART_Receive(&huart3,(uint8_t *)rxbuf,strlen(rxbuf),300);
HAL_Delay(100);
HAL_UART_Transmit(&huart1,(uint8_t *)rxbuf,strlen(rxbuf),300);//to Uart1 for debugging the response
rxbuf[0]='\0';
HAL_Delay(10000);
HAL_UART_Transmit(&huart3,(uint8_t *)"ATH\r\n",strlen("ATH\r\n"),1000);
HAL_Delay(100);
HAL_UART_Receive(&huart3,(uint8_t *)rxbuf,strlen(rxbuf),300);
HAL_Delay(100);
HAL_UART_Transmit(&huart1,(uint8_t *)rxbuf,strlen(rxbuf),300);//to Uart1 for debugging the response
rxbuf[0]='\0';
}
void sim800_sms(void) // function 1 working
{
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CMGF=1\r\n",strlen("AT+CMGF=1\r\n"),1000);
//HAL_Delay(500);
//HAL_UART_Transmit(&huart1,(uint8_t *)"AT+CMGS=\"+91xxxxxxxxxx\"\r\n",strlen("AT+CMGS=\"+91xxxxxxxxxx\"\r\n"),1000);
//HAL_Delay(500);
//HAL_UART_Transmit(&huart1,(unsigned char *)"it is working",strlen("it is working"),1000);
//HAL_Delay(500);
//HAL_UART_Transmit(&huart1,(uint8_t *)&x,1,10);
HAL_Delay(500);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CMGS=\"+91xxxxxxxxxxx\"\r\n",strlen("AT+CMGS=\"+91xxxxxxxxxx\"\r\n"),1000);
HAL_Delay(500);
HAL_UART_Transmit(&huart3,(unsigned char *)msg_str,strlen((const char *)msg_str),1000);
HAL_Delay(500);
HAL_UART_Transmit(&huart3,(uint8_t *)&x,1,10);
HAL_Delay(5000);
}
void send_sms(void) // function 2 working
{
LED_GPIO_Port -> BRR = LED_Pin;
send_str[0] = '\0';
sprintf(send_str,"AT+CMGF=1\r\n");
HAL_UART_Transmit(&huart3,(unsigned char *)send_str,strlen(send_str),1000);
HAL_Delay(1000);
send_str[0] = '\0';
sprintf(send_str,"AT+CMGS=\"+91%s\"\r\n",Num_str);
HAL_UART_Transmit(&huart3,(unsigned char *)send_str,strlen(send_str),1000);
HAL_Delay(1000);
sprintf(sending_sms_str,"HELLO\r\n");
HAL_UART_Transmit(&huart3,(unsigned char *)sending_sms_str,strlen(sending_sms_str),1000);
//HAL_Delay(10);
//HAL_UART_Transmit(&huart1,(unsigned char*)S,1,1000); // or SUB
SUB
HAL_Delay(1000);
LED_GPIO_Port -> BSRR = LED_Pin;
}
void sim800_gprs(void)
{
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r\n",strlen("AT\r\n"),1000);
HAL_Delay(300);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CIPSHUT\r\n",strlen("AT+CIPSHUT\r\n"),1000);
HAL_Delay(300);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CIPMUX=0\r\n",strlen("AT+CIPMUX=0\r\n"),1000);
HAL_Delay(300);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CGATT=1\r\n",strlen("AT+CGATT=1\r\n"),1000);
HAL_Delay(300);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CSTT=\"www\",\"\",\"\"\r\n",strlen("AT+CSTT=\"www\",\"\",\"\"\r\n"),1000);
HAL_Delay(2000);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CIICR\r\n",strlen("AT+CIICR\r\n"),5000);
HAL_Delay(2000);
HAL_UART_Transmit(&huart3,(uint8_t *)"AT+CIFSR\r\n",strlen("AT+CIFSR\r\n"),1000);
HAL_Delay(1000);
HAL_UART_Transmit(&huart1,(uint8_t *)"All cmd sent\r\n",strlen("All cmd sent\r\n"),1000);
}
//---------------------------------------------------------------------//
/* 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_USART1_UART_Init();
MX_USART3_UART_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
sim800_init();
sim800_gprs();
//sim800_call();
//sim800_test();
//sim800_init();
//sim800_call(); // working but reliability low
//send_sms(); // working but reliability very low
// sim800_sms(); // working
//HAL_Delay(25000);
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
/**
* #brief System Clock Configuration
* #retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {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();
}
}
/**
* #brief USART1 Initialization Function
* #param None
* #retval None
*/
static void MX_USART1_UART_Init(void)
{
/* USER CODE BEGIN USART1_Init 0 */
/* USER CODE END USART1_Init 0 */
/* USER CODE BEGIN USART1_Init 1 */
/* USER CODE END USART1_Init 1 */
huart1.Instance = USART1;
huart1.Init.BaudRate = 9600;
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();
}
/* USER CODE BEGIN USART1_Init 2 */
/* USER CODE END USART1_Init 2 */
}
/**
* #brief USART3 Initialization Function
* #param None
* #retval None
*/
static void MX_USART3_UART_Init(void)
{
/* USER CODE BEGIN USART3_Init 0 */
/* USER CODE END USART3_Init 0 */
/* USER CODE BEGIN USART3_Init 1 */
/* USER CODE END USART3_Init 1 */
huart3.Instance = USART3;
huart3.Init.BaudRate = 9600;
huart3.Init.WordLength = UART_WORDLENGTH_8B;
huart3.Init.StopBits = UART_STOPBITS_1;
huart3.Init.Parity = UART_PARITY_NONE;
huart3.Init.Mode = UART_MODE_TX_RX;
huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart3.Init.OverSampling = UART_OVERSAMPLING_16;
if (HAL_UART_Init(&huart3) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART3_Init 2 */
/* USER CODE END USART3_Init 2 */
}
/**
* #brief GPIO Initialization Function
* #param None
* #retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(LED_GPIO_Port, LED_Pin, GPIO_PIN_RESET);
/*Configure GPIO pin : LED_Pin */
GPIO_InitStruct.Pin = LED_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(LED_GPIO_Port, &GPIO_InitStruct);
}
/* 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

Answer 1

I would suggest the following to debug the problems you're facing:
You need to make sure that your UART code is working correctly, to
do that you can connect your STM32 to a serial terminal on your PC
via an FTDI cable and check if the messages sent from the STM32 are
received on the serial terminal.
Once step (1) is resolved, you need to check that you are powering
your SIM800 module correctly (ie: correct power pin and enough
current).
Once step (2) is resolved try to connect the SIM800 to your PC via
an FTDI cable and send & receive AT commands and responses via a serial monitor.
Back to the code here are some simple examples on how to send an AT command and wait for its known response:
With Echo:
/* Wait at most 1000 ms for the command to be sent completely */
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r", (sizeof("AT\r")-1), 1000);
/* Wait 5000 ms for response with echo */
HAL_UART_Receive(&huart3, (uint8_t *)rx_buffer, (sizeof("AT\r\r\nOK\r\n")-1), 5000);
Without echo:
/* Wait at most 1000 ms for the command to be sent completely */
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r", (sizeof("AT\r")-1), 1000);
/* Wait 50000 ms for response without echo */
HAL_UART_Receive(&huart3, (uint8_t *)rx_buffer, (sizeof("\r\nOK\r\n")-1), 5000);
OR you can do it asynchronously via the UART receive callback:
With Echo:
/* Wait at most 1000 ms for the command to be sent completely */
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r", (sizeof("AT\r")-1), 1000);
/* This will raise a callback when the response length is reached */
HAL_UART_Receive_IT(&huart3, (uint8_t *)rx_buffer, (sizeof("AT\r\r\nOK\r\n")-1));
Without echo:
/* Wait at most 1000 ms for the command to be sent completely */
HAL_UART_Transmit(&huart3,(uint8_t *)"AT\r", (sizeof("AT\r")-1), 1000);
/* This will raise a callback when the response length is reached */
HAL_UART_Receive_IT(&huart3, (uint8_t *)rx_buffer, (sizeof("\r\nOK\r\n")-1));
Callback:
HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
if(huart->Instance == USART3)
{
/* if you are here then you received a response */
}
}