Question

我正在尝试使用atmega324p从外部eeprom读取数据。问题出现在for循环中。我无法读取4页（4 x 64B）的EEPROM数据。如果我将循环计数器从4增加到5，我会陷入无限循环的UART0传输。这是我目前的代码：

// create an array to store the logged off eeprom data to and for use 
//in sending bytes to teraterm. Location 0-15 hold first assertLog
UChar aucTeraTermMsgBuf[EXT_EEPROM_PAGE_LENGTH]; //length is 64B 

void TeraTermOutputMsg(void)
{        
//configure UART0 to what I want for my purposes
TeraTermConfigUART0();

//define the starting address to read from.  Each time the button pushed 
//we will begin reading from the very beginning of memory array (aka it is a full dump of EEPROM stored data)
UInt16 eepromReadAddress = 0x0000;

//Loop thru whole EEPROM 1 page of data at a time and send it.  
//Cant get past 4 pages though.... TODO FIX THIS 
for(UInt16 uspagesSent = 0; uspagesSent < 4; uspagesSent++)
 {
    //get one page of the log from the specified address in the eeprom and store it to an 
    //array of type UChar and length of 1 page (64B).
    TeraTermGetAssertLog(eepromReadAddress);

    //send the 1 page of eeprom data to teraterm
    TeraTermUART0Transmit();

    //update the next read address to pass the get log function
    eepromReadAddress += EXT_EEPROM_PAGE_LENGTH; //length is 64Bytes

 }

}

//Gets data from the EEPROM and puts it into an array in prep to send out UART0 to PC
void TeraTermGetAssertLog(UInt16 nextReadAddress)
{
//initialize the array we are storing the EEPROM data to
for(UInt16 i = 0; i < EXT_EEPROM_PAGE_LENGTH; i++)
    aucTeraTermMsgBuf[i] = 0;

//this will read the bytes from EEPROM and load them into an array
ExtEEPROM_Read(aucTeraTermMsgBuf, nextReadAddress);             
}

//function that will output string of data out to PC
void TeraTermUART0Transmit(void)
{
//array to encode the tera term message to using sprintf.  
//Takes each hex value (0x_ _ ) and converts it to ASCII code for those numbers/letters
UChar encodeMsgArray[2];
//next character to be transmitted
UChar nextChar;

//counter for bytes sent.  After 16 (1 log) want to send new line break point
UInt8 byteCount = 0x01;

//loop through the message buffer and send output to teraterm
for(UInt16 i = 0; i < EXT_EEPROM_PAGE_LENGTH; i++)
{
    //get next char from the TeraTerm output buffer array
    nextChar = aucTeraTermMsgBuf[i];

    //convert the char hex value into the ascii code for the 2 letters/numbers present in 1 hex value
    sprintf(encodeMsgArray, "%2.2x", nextChar);

    //transmit those two ascii codes on the uart0 to teraterm with a space after
    UART0_Transmit(encodeMsgArray[0]);
    UART0_Transmit(encodeMsgArray[1]);
    UART0_Transmit(" ");    //send a space so text file parser can distinguish between bytes of data


    //if we have sent a whole assert log, print next to new line
    if(byteCount == 16)
    {
        byteCount = 0x00;
        sprintf(encodeMsgArray, "\r\n");
        UART0_Transmit(encodeMsgArray[0]);
        UART0_Transmit(encodeMsgArray[1]);

    }

    ++byteCount;
}

}

我知道阅读可能有点太多了，但我很难过。当我将循环计数器变量（pagesSent）放入监视窗口时，它会被优化，当我声明为volatile时它仍然会被优化，但是当最大值设置为4时，循环正常退出，但如果最大值高于4卡住...... 谢谢你的帮助。

Answer 1

我通过查看optmization帖子来解决这个问题。如果未使用循环变量，则编译器将变量设置为最大值。我不完全理解编译器或优化。但话虽如此，如果我只是将uspagesSent变量传递给TeraTermUART0Transmit，然后在该函数中将其乘以64以获得下一个（页面）地址，一切都很好。希望这有助于有人下线。以下是有用帖子的链接：for loop being ignored (optimized?) out

EEPROM数据到TeraTerminal

1 个答案: