串口放在主程序外正常，与正常程序一起就有问题。求指教

chenshoubao0 · 发表于 2020-4-27 14:35:17

   u8 tx = 0xaabb>>8;

while( 1 )
{
#if 0
IWDG_ReloadCounter();

LedBatteryIndicator();
Check_System();
System_Control();

STMFLASH_Read(0X08004000,(u16*)datatemp,1);
if(datatemp[0] != ( (Flag_2S << 3)|( FLAG_TIME << 2 ) | ( FLAG_SAFTY << 1 ) | Flag_Retract ))
{
SystemState_Write();
}

     UART_send_byte(2);

// UART_send_byte(tx);
UART_send_byte(0xaabb&0xff);
   #endif
UART_send_byte(0xaabb&0xff);
}
问题描述：这样串口可以正常发送数据，发出数据aa

   u8 tx = 0xaabb>>8;
while( 1 )
{
#if 1
IWDG_ReloadCounter();

LedBatteryIndicator();
Check_System();
System_Control();

STMFLASH_Read(0X08004000,(u16*)datatemp,1);
if(datatemp[0] != ( (Flag_2S << 3)|( FLAG_TIME << 2 ) | ( FLAG_SAFTY << 1 ) | Flag_Retract ))
{
SystemState_Write();
}
UART_send_byte(0xaabb&0xff);
   #endif
// UART_send_byte(0xaabb&0xff);
}
问题描述：串口发送放到这边发出的就是错的，只是简单的取了个八位。

   u8 tx = 0xaabb>>8;
while( 1 )
{
#if 0
IWDG_ReloadCounter();

LedBatteryIndicator();
Check_System();
System_Control();

STMFLASH_Read(0X08004000,(u16*)datatemp,1);
if(datatemp[0] != ( (Flag_2S << 3)|( FLAG_TIME << 2 ) | ( FLAG_SAFTY << 1 ) | Flag_Retract ))
{
SystemState_Write();
}

     UART_send_byte(2);

UART_send_byte(tx);
// UART_send_byte(0xaabb&0xff);
   #endif
//UART_send_byte(0xaabb&0xff);
}
问题描述：取八位赋值给一个变量再来发，又正常。

问题：为什么直接取八位放到主程序里发送是有问题的，直接在飞思卡尔的单片机上这样都是ok的，用的iar编译器，目前是keil