我有一个GSM模块通过硬件UART与我的微控制器交谈。当我接收到小数据时，一切都工作了。当我试图获得存储在SIM卡中的所有短信列表时，我得到UART缓冲区溢出错误。
我有一个动态字符串函数，它在使用malloc的缓冲区中附加每个接收到的字符。这就是我接受的方式。我把有问题的那行注释掉了。
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，如果你有关于malloc很慢的线索，或者如果你知道UART被UART接收中断中断是一个问题。如何在不降低UART比特率而不增加时钟速度的情况下解决这个问题?
更新:
调试后，我确信malloc正在工作(如果malloc失败，我得到一个断言)，所以我的下一个猜测是appendChar很慢。虽然只是为了阅读短信，我将尝试马特奥建议使用固定字符数组一次一个短信(每条短信最多160个字符+发件人信息)
更新2 -新代码
我成功了，但我很幸运。代码中有一行我不明白为什么我需要它。我有8Mhz和19200 UART比特率。我猜是时间不对。
这是如果我删除函数不起作用的行:
_delay_us(150); // TODO: WEIRD KNOWN BUG!!!
这里是整个函数:
/**
* @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] = ' ';
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;
}
读取基于堆的动态内存分配工作原理;这太宽泛了，无法解释。点，它的运行时是不确定的，它可能会导致堆碎片，所以你最终不会在一段时间后得到任何块。
更进一步，我认为你正在印刷一些东西。这也可能是一个问题。总而言之:不要使用运行时间(可能)超过实时场景可接受时间的函数(UART接收器施加了处理时间的上限)。
使用足够长的缓冲区来获得最大值。包的大小。如果你坚持使用线性处理顺序，你必须为这种情况做好准备。
更好的方法是使用中断来接收数据。这样，您就可以使用两个交替的缓冲区(每个缓冲区的max。大小)，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。
注意:除非你真的必须和考虑了所有的含义，否则不要强制转换。