uint8_t cmd[2];
uint8_t val[1];
cmd[0]='S';
cmd[1]='7';
val[0]=1;
HAL_UART_Transmit(&uart1, cmd, 2, 1);
HAL_UART_Transmit(&uart1, val, 1, 1);

uint8_t cmd[4];
cmd[0]='S';
cmd[1]='7';
cmd[2]=',';
cmd[3]='1';
HAL_UART_Transmit(&uart1, cmd, 4, 1);

int main(void){
uint8_t cmd[]={"$$$"};;
uint8_t reboot[]={"R,1\r"};   
uint8_t spd96[]={"SU,96\r"};
uint8_t def_settings[]={"SF,1\r"};

HAL_Init();
SystemClock_Config();
MX_USART1_UART_Init();
BT_ON;   
BT_RES_OFF;
HAL_UART_Transmit(&huart1, cmd, strlen(cmd), 0xFFFFFF);
HAL_Delay(500);      
HAL_UART_Transmit(&huart1, spd96, strlen(spd96), 0xFFFFFF);
BT_RES_ON;
HAL_Delay(500);
BT_RES_OFF;
HAL_Delay(500);
HAL_UART_Transmit(&huart1, def_settings, strlen(def_settings), 0xFFFFFF);
...
}

void MX_USART1_UART_Init(void)
{

  huart1.Instance = USART1;
  huart1.Init.BaudRate = 9600;//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__);
  }

}

HAL_UART_Transmit(&huart1, cmd, strlen(cmd), 0xFFFFFF);
   HAL_Delay(2000);      
   HAL_UART_Receive(&huart1, reply, 3, 0xFFFFFF);
   HAL_UART_Transmit(&huart1, def_settings, strlen(def_settings), 0xFFFFFF);

   HAL_UART_Transmit(&huart1, reboot, strlen(reboot), 0xFFFFFF);