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How to read data correctly from NEO-6M GPS module?

M7890.1
Associate III

Hi.

I am trying to read data from the GPS module using USART1 and then send to to a serial monitor through USART2. It ended up not printing the information correctly on the serial monitor. (I have tried to connect the GPS module to a FTDI module directly and there are data showing on the serial monitor)

My code:

/* USER CODE BEGIN Header */
/**
 ******************************************************************************
 * @file           : main.c
 * @brief          : Main program body
 ******************************************************************************
 * @attention
 *
 * <h2><center>&copy; Copyright (c) 2021 STMicroelectronics.
 * All rights reserved.</center></h2>
 *
 * This software component is licensed by ST under BSD 3-Clause license,
 * the "License"; You may not use this file except in compliance with the
 * License. You may obtain a copy of the License at:
 *                        opensource.org/licenses/BSD-3-Clause
 *
 ******************************************************************************
 */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
 
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
 
/* USER CODE END Includes */
 
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
 
/* 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 ---------------------------------------------------------*/
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;
 
/* USER CODE BEGIN PV */
 
/* 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 */
 
/* 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 */
	uint8_t buffer[128] = {'\0'};
	/* 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) {
		/* USER CODE END WHILE */
		HAL_UART_Receive(&huart1, buffer, 8, 100);
		HAL_UART_Transmit(&huart2, buffer, sizeof(buffer), 100);
 
		/* 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_HSI;
	RCC_OscInitStruct.HSIState = RCC_HSI_ON;
	RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
	RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
	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_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();
	}
}
 
/**
 * @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 USART2 Initialization Function
 * @param None
 * @retval None
 */
static void MX_USART2_UART_Init(void) {
 
	/* USER CODE BEGIN USART2_Init 0 */
 
	/* USER CODE END USART2_Init 0 */
 
	/* USER CODE BEGIN USART2_Init 1 */
 
	/* USER CODE END USART2_Init 1 */
	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();
	}
	/* USER CODE BEGIN USART2_Init 2 */
 
	/* USER CODE END USART2_Init 2 */
 
}
 
/**
 * @brief GPIO Initialization Function
 * @param None
 * @retval None
 */
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.
 * @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 */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

And here's part of the output on the serial monitor:

0693W00000D1pAQQAZ.png

12 REPLIES 12

I forgot to mention that I used the Blue Pill board which is having a STM32F103CBT6 on board. This MCU doesn't have HAL_UARTEx_ReceiveToIdle right? In that case, any suggestion on how to receive data from UART if the number of bytes is not known?

If you are not sure about the number of bytes to receive use an interrupt.

Setup a receive interrupt for one byte. In the callback, check if that byte is the end of frame character, for you '\r'.

If it is not, setup another one and keep going like that. Simply increment the destination pointer every time you setup a new receive interrupt.

Receive one byte at a time, and line buffer locally. Use that to resync the buffer if you encounter a $ symbol, and copy to a processing buffer when you have a complete line to parse.

The F1 is going to interrupt for every byte received anyway, the HAL callback mechanism only calls you when your request is complete, perhaps to decimate loading from it's rather bloated implementation.

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