Working with Structs on a AVR microcontroller

Question

I am trying to save a structure of uint8_t and uint16_t members from an ATMega32 microcontroller into an external EEPROM. For this reason I wrote a function to save this struct and another to read it again. In the read function the address is passed in as pointer. Inside the function the value is printed via RS232, but I get the wrong data as well as a wrong adress (terminal output below). But I don't change the adress (ass you can see), I have no idea why the output it '600'. The functions to save a single byte work fine, I have tested them separately.

This is the main program where I am trying to prepare the struct, save it and finally read it again. Under the main program

    uint16_t testSaveAddr = 20;
    uint16_t testLoadAddr = 20;
    dataEntry testData;
    dataEntry loadData;


    testData.airPressure = 1023;
    testData.batteryCharge = 140;
    testData.dayOfMonth = 20;
    testData.hours24 = 11;
    testData.humidityInside = 63;
    testData.humidityOutside = 80;
    testData.lightVal = 123;
    testData.minutes = 30;
    testData.month = 11;
    testData.rain = 0;
    testData.temperatureInside = 240;
    testData.temperatureOutside = 130;
    testData.windDirection = 4;
    testData.windVelocity = 300;
    testData.yearS70 = 35;

    saveDataSet(EEPROM_1_ADDR,testData,&testSaveAddr);
    _delay_ms(200);
    readDataSet(EEPROM_1_ADDR,&testLoadAddr,&loadData);
    _delay_ms(200);

uint8_t saveDataSet (char address_device, dataEntry dS, uint16_t *firstAvailableAddr)
{
    uart_puts("*** SAVING NOW ****\n");
    //hum -> timeStamp, LOW -> HIGH
    uint16_t addr = *firstAvailableAddr;
    char text[20];

    sprintf(text,"1.| addr: %d\t data: %d\n",addr,dS.humidityOutside);
    uart_puts(text);

    save_byte_to_eeprom(address_device, addr++, dS.humidityOutside);

    sprintf(text,"1.| addr: %d\t data: %d\n",addr,dS.humidityInside);
    uart_puts(text);

    save_byte_to_eeprom(address_device, addr++, dS.humidityInside);
    save_byte_to_eeprom(address_device, addr++, (dS.temperatureOutside)&0xFF);
    save_byte_to_eeprom(address_device, addr++, ((dS.temperatureOutside)>>8)&0xFF);
    save_byte_to_eeprom(address_device, addr++, (dS.temperatureInside)&0x0FF);
    save_byte_to_eeprom(address_device, addr++, ((dS.temperatureInside)>>8)&0xFF);
    save_byte_to_eeprom(address_device, addr++, (dS.airPressure)&0xFF);
    save_byte_to_eeprom(address_device, addr++, ((dS.airPressure)>>8)&0xFF);
    save_byte_to_eeprom(address_device, addr++, (dS.windVelocity)&0xFF);
    save_byte_to_eeprom(address_device, addr++, ((dS.windVelocity)>>8)&0xFF);
    save_byte_to_eeprom(address_device, addr++, dS.windDirection);
    save_byte_to_eeprom(address_device, addr++, dS.lightVal);
    save_byte_to_eeprom(address_device, addr++, dS.rain);
    save_byte_to_eeprom(address_device, addr++, dS.batteryCharge);

    //timeStamp
    save_byte_to_eeprom(address_device, addr++, dS.minutes);
    save_byte_to_eeprom(address_device, addr++, dS.hours24);
    save_byte_to_eeprom(address_device, addr++, dS.dayOfMonth);
    save_byte_to_eeprom(address_device, addr++, dS.month);
    save_byte_to_eeprom(address_device, addr++, dS.yearS70);

    //update, when dataset is fully stored, in case of an error
    *firstAvailableAddr = addr;
    return 1;
}

uint8_t readDataSet (char address_device, uint16_t *nextDSaddr, dataEntry dS)
{
    uint16_t addr = *nextDSaddr;
    char text[20];
    uart_puts("**** READING NOW ****");

    dS->humidityOutside = read_byte_from_eeprom(address_device,addr);
    sprintf(text,"1.| addr: %d\t data: %d\n",addr,dS->humidityOutside);
    uart_puts(text);
    addr++;

    dS->humidityInside = read_byte_from_eeprom(address_device,addr++);

    uint8_t tempOutLow = read_byte_from_eeprom(address_device,addr++);
    uint8_t tempOutHigh = read_byte_from_eeprom(address_device,addr++);
    dS->temperatureOutside = (tempOutHigh<<8)+tempOutLow;


    uint8_t tempInLow = read_byte_from_eeprom(address_device,addr++);
    uint8_t tempInHigh = read_byte_from_eeprom(address_device,addr++);
    dS->temperatureInside = (tempInHigh<<8)+tempInLow;

    uint8_t airPressLow = read_byte_from_eeprom(address_device,addr++);
    uint8_t airPressHigh = read_byte_from_eeprom(address_device,addr++);
    dS->airPressure = (airPressHigh<<8)+airPressLow;

    uint8_t windVelLow = read_byte_from_eeprom(address_device,addr++);
    uint8_t windVelHigh = read_byte_from_eeprom(address_device,addr++);
    dS->airPressure = (windVelHigh<<8)+windVelLow;

    dS->windDirection = read_byte_from_eeprom(address_device,addr++);
    dS->lightVal = read_byte_from_eeprom(address_device,addr++);
    dS->rain = read_byte_from_eeprom(address_device,addr++);
    dS->batteryCharge = read_byte_from_eeprom(address_device,addr++);

    //timestamp
    dS->minutes = read_byte_from_eeprom(address_device,addr++);
    dS->hours24 = read_byte_from_eeprom(address_device,addr++);
    dS->dayOfMonth = read_byte_from_eeprom(address_device,addr++);
    dS->month = read_byte_from_eeprom(address_device,addr++);
    dS->yearS70 = read_byte_from_eeprom(address_device,addr++);

    *nextDSaddr = addr;
    return 1;
}

Terminal output:

*** SAVING NOW ****
1.| addr: 20     data: 80
1.| addr: 21     data: 63
**** READING NOW ******
1.| addr: 600    data: 255

Answer 1

I think you may be overwriting the contents of the testLoadAddr variable by overflowing the text buffer when you generate the strings in saveDataSet. You have only allowed for 20 chars but you have 2 digit numbers so have a string of 24 chars including the terminating NUL. This is certainly a problem though exactly which variables get affected will depend on the stack layout created by the compiler.