修正UART溢出
我有一个GSM模块与我的微控制器通过硬件UART交谈。当我收到小数据时，一切都正常。当我试图获取存储在SIM卡中的所有SMS消息的列表时，我会得到UART缓冲区溢出错误。
我有一个动态字符串函数，它在使用malloc的缓冲区中追加每个接收到的字符。我就是这样接受的。我把引起问题的那一行评论掉了。
while( uart_available() > 0 )
{
/*
* There are characters in the buffer so
* keep receiving until buffer in empty.
*/
unsigned int c = uart_getc();
if ( c & UART_NO_DATA )
{
/*
* No data available from UART. This is not an error.
*/
error( AT, "No error but - No uart data" );// TODO: Delete it. It is not an error actually.
}
else if ( c & UART_FRAME_ERROR )
{
/* Framing Error detected, i.e no stop bit detected */
errorOccured( ER_UART_FRAME_ERROR );
error( AT, "Frame error" );
}
else if ( c & UART_OVERRUN_ERROR )
{
/*
* Overrun, a character already present in the UART UDR register was
* not read by the interrupt handler before the next character arrived,
* one or more received characters have been dropped.
*/
errorOccured( ER_UART_OVERRUN_ERROR );
error( AT, "Overrun error" );
}
else if ( c & UART_BUFFER_OVERFLOW )
{
/*
* We are not reading the receive buffer fast enough,
* one or more received characters have been dropped.
*/
errorOccured( ER_UART_BUFFER_OVERFLOW );
error( AT, "Buffer overflow error" );
}
else
{
/*
* There are data available add them to cString.
*/
appendChar( data, (const char)c );// This line is slow and causes UART overflow.
if ( *data == 0 )
{
/*
* Report bad pointer.
*/
errorOccured( ER_SIM900_BAD_POINTER );
error( AT, "Bad pointer" );
}
/*
* We received something so change the flag
* even if an error occurs in the next loop.
*/
isReceivedData = true;
}
}我想问你们，你们是否知道malloc是慢的，或者你是否知道UART被UART中断了，接收中断是个问题。如何在不提高时钟速度的情况下不降低UART比特率来解决这一问题？
更新：
调试之后，我确定malloc正在工作(如果malloc失败了，我会得到一个断言)，所以我的下一个猜测是appendChar是慢的。虽然只用于阅读SMS，但我会尝试使用Mateo建议的固定字符数组，每次使用一个SMS (每个SMS最多160个字符+发件人信息)。
更新2-新代码
我成功了，但我幸运地做到了。代码中有一行代码，我不明白为什么需要它。我有8 8Mhz和19200 UART比特率。我想时机有点问题。
如果我移除函数，这一行就不能工作：
_delay_us(150); // TODO: WEIRD KNOWN BUG!!!在这里，整个功能：
/**
* @brief Receives raw data from SIM900.
*
* @param data Get SIM900's raw data on exit.
*
* @return True if at least one character received.
*/
bool SIM900_receive( cString* data )
{
/*
* Because we append chars we need to init it.
*/
#define SIM900_MAX_RECEIVE_CHARACTERS 300
char temp[SIM900_MAX_RECEIVE_CHARACTERS+1];
strcpy_P( temp, PSTR("") );
int32_t i = 0;
/*
* There are no received data so far.
*/
bool isReceivedData = false;
/*
* Check UART buffer
*/
while( uart_available() > 0 )
{
/*
* There are characters in the buffer so
* keep receiving until buffer in empty.
*/
unsigned int c = uart_getc();
_delay_us(150); // TODO: WEIRD KNOWN BUG!!!
if ( c & UART_NO_DATA )
{
/*
* No data available from UART. This is not an error.
*/
error( AT, "No error but - No uart data" );// TODO: Delete it. It is not an error actually.
}
else if ( c & UART_FRAME_ERROR )
{
/* Framing Error detected, i.e no stop bit detected */
errorOccured( ER_UART_FRAME_ERROR );
error( AT, "Frame error" );
}
else if ( c & UART_OVERRUN_ERROR )
{
/*
* Overrun, a character already present in the UART UDR register was
* not read by the interrupt handler before the next character arrived,
* one or more received characters have been dropped.
*/
errorOccured( ER_UART_OVERRUN_ERROR );
error( AT, "Overrun error" );
}
else if ( c & UART_BUFFER_OVERFLOW )
{
/*
* We are not reading the receive buffer fast enough,
* one or more received characters have been dropped.
*/
errorOccured( ER_UART_BUFFER_OVERFLOW );
error( AT, "Buffer overflow error" );
}
else
{
/*
* There are data available add them to cString.
*/
if( i<SIM900_MAX_RECEIVE_CHARACTERS )
{
temp[i] = (char) c;
temp[i+1] = '\0';
i++;
}
/*
* We received something so change the flag
* even if an error occurs in the next loop.
*/
isReceivedData = true;
}
}
copyString( data, temp );
/*
* Exit.
*/
return isReceivedData;
}回答 1
Stack Overflow用户
发布于 2015-09-18 11:31:23
阅读基于堆的动态内存分配是如何工作的；这太宽泛了，无法解释。它的运行时是不确定的，它可能会导致堆的碎片，因此在一段时间后，您最终将不会得到任何块。
你还在印些我猜的东西。这也可能是个问题。总之:不要使用(可能)运行时间超过实时场景中可接受的运行时间的函数( UART接收器规定处理时间的上限)。
使用足够长的缓冲区来获得最大值。包的大小。无论如何，如果您坚持使用线性处理序列，那么您必须为这种情况做好准备。
一种更好的方法是使用中断来增强数据。这样，您可以使用两个交替缓冲区(每个最大)。并在正常代码中处理一个缓冲区，同时通过中断处理程序接收下一个缓冲区。
注意:除非你真的必须和考虑了所有的含义，否则不要进行强制转换。通常情况下，转换是接口设计不良的信号。
https://stackoverflow.com/questions/32649762
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