Question
Trying to Generate a sbus
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I am trying to generate a sbus signal for radio transmission in drones. imhave tried this code. in oscilloscope, uart output is showing, but qgc is not detecting sbus. i do pass a 16 channel array to convert into sbus. the project is as below:-
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2025 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"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
#include <string.h>
/* 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 ---------------------------------------------------------*/
TIM_HandleTypeDef htim3;
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;
/* USER CODE BEGIN PV */
uint16_t channels[16] = { 1000, 900, 1200, 900, 1500, 1500, 1500, 1500,
1500, 1500, 1500, 1500, 1500, 1500, 1500, 1500 };
/* 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);
static void MX_TIM3_Init(void);
/* USER CODE BEGIN 0 */
void SBUS_GenerateFrame(uint16_t channels[16], uint8_t sbus_data[25])
{
// memset(sbus_data, 0, 25);
uint32_t ch[16];
for (int i = 0; i < 16; i++) {
ch[i] = channels[i];
// & 0x07FF; // 11-bit channel data
}
sbus_data[0] = 0x0F;
sbus_data[1] = (uint8_t)(ch[0] & 0xFF);
sbus_data[2] = (uint8_t)((ch[0] >> ?? | (ch[1] << 3));
sbus_data[3] = (uint8_t)((ch[1] >> 5) | (ch[2] << 6));
sbus_data[4] = (uint8_t)(ch[2] >> 2);
sbus_data[5] = (uint8_t)((ch[2] >> 10) | (ch[3] << 1));
sbus_data[6] = (uint8_t)((ch[3] >> 7) | (ch[4] << 4));
sbus_data[7] = (uint8_t)((ch[4] >> 4) | (ch[5] << 7));
sbus_data[8] = (uint8_t)(ch[5] >> 1);
sbus_data[9] = (uint8_t)((ch[5] >> 9) | (ch[6] << 2));
sbus_data[10] = (uint8_t)((ch[6] >> 6) | (ch[7] << 5));
sbus_data[11] = (uint8_t)(ch[7] >> 3);
sbus_data[12] = (uint8_t)(ch[8] & 0xFF);
sbus_data[13] = (uint8_t)((ch[8] >> ?? | (ch[9] << 3));
sbus_data[14] = (uint8_t)((ch[9] >> 5) | (ch[10] << 6));
sbus_data[15] = (uint8_t)(ch[10] >> 2);
sbus_data[16] = (uint8_t)((ch[10] >> 10) | (ch[11] << 1));
sbus_data[17] = (uint8_t)((ch[11] >> 7) | (ch[12] << 4));
sbus_data[18] = (uint8_t)((ch[12] >> 4) | (ch[13] << 7));
sbus_data[19] = (uint8_t)(ch[13] >> 1);
sbus_data[20] = (uint8_t)((ch[13] >> 9) | (ch[14] << 2));
sbus_data[21] = (uint8_t)((ch[14] >> 6) | (ch[15] << 5));
sbus_data[22] = (uint8_t)(ch[15] >> 3);
sbus_data[23] = 0x00; // flags
sbus_data[24] = 0x00; // end byte
// printf("sbus_data= ");
// for(int i=0;i<16;i++)
// printf(" %d ",sbus_data[i] );
// printf("\r\n");
}
void SBUS_Transmit(UART_HandleTypeDef* huart, uint16_t channels[16])
{
uint8_t sbus_data[25];
SBUS_GenerateFrame(channels, sbus_data);
HAL_UART_Transmit(huart, sbus_data, 25, HAL_MAX_DELAY);
}
/* USER CODE END 0 */
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();
/* 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();
MX_TIM3_Init();
/* USER CODE BEGIN 2 */
HAL_TIM_Base_Start_IT(&htim3);
/* USER CODE END 2 */
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 TIM3 Initialization Function
* @PAram None
* @retval None
*/
static void MX_TIM3_Init(void)
{
/* USER CODE BEGIN TIM3_Init 0 */
/* USER CODE END TIM3_Init 0 */
TIM_ClockConfigTypeDef sClockSourceConfig = { 0 };
TIM_MasterConfigTypeDef sMasterConfig = { 0 };
/* USER CODE BEGIN TIM3_Init 1 */
/* USER CODE END TIM3_Init 1 */
htim3.Instance = TIM3;
htim3.Init.Prescaler = 0;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 139;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
if (HAL_TIM_Base_Init(&htim3) != HAL_OK) {
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK) {
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) !=
HAL_OK) {
Error_Handler();
}
/* USER CODE BEGIN TIM3_Init 2 */
/* USER CODE END TIM3_Init 2 */
}
/**
* @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 = 100000;
huart1.Init.WordLength = UART_WORDLENGTH_8B;
huart1.Init.StopBits = UART_STOPBITS_2;
huart1.Init.Parity = UART_PARITY_EVEN;
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 = 100000;
huart2.Init.WordLength = UART_WORDLENGTH_8B;
huart2.Init.StopBits = UART_STOPBITS_2;
huart2.Init.Parity = UART_PARITY_EVEN;
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_InitTypeDef GPIO_InitStruct = { 0 };
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);
/*Configure GPIO pin : PC13 */
GPIO_InitStruct.Pin = GPIO_PIN_13;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* USER CODE BEGIN 4 */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef * htim)
{
if (htim->Instance == TIM3) {
// Debug LED blink
SBUS_Transmit(&huart2, channels); // Send SBUS frame every 14ms
}
}
/* 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) {
}
#endif /* USE_FULL_ASSERT */