error: lvalue required as left operand of assignment, error: void value not ignored as it ought to be

Question

Im getting these errors:

error: lvalue required as left operand of assignment
error: void value not ignored as it ought to be

Basically I have a i2c capacitive touch controller that I am constantly scanning then checking the scanned data and then doing an d actions if required then repeating.

Here is my code:

#include <avr/io.h>
#include <util/delay.h> 
#include "i2cmaster.h"

#define mpr03x 0x4A

int main(void)
{
    unsigned char tou;

    DDRA = 0xff;
    DDRB = 0xff;
    PORTA = 0x03;
    _delay_ms(500);
    PORTA = 0x00;

    i2c_init();     //Initialize I2C

    i2c_start_wait(mpr03x+I2C_WRITE);   //Set device address and write mode
    i2c_write(0x44);                    //Write address = 68
    i2c_write(0x03);                    //Calibration = ON, Runmode = 1, Enabled = ELE0, ELE1, ELE2

    while(1)
    {
        PORTA = 0x01;
        i2c_start_wait(mpr03x=I2C_WRITE);   //Set device address and write mode
        i2c_write(0x00);                    //Write address = 68
        i2c_rep_start(mpr03x+I2C_READ);     // set device address and read mode
        tou = i2c_readNak;
        i2c_stop;

        if(tou == 0x00);                    //If no pads are pressed
        {
            PORTA = 0x00;
            _delay_ms(1);
        }
        else
        {
            if(tou == 0x01);                //If pad 1 is pressed
            {
                PORTA = 0x05;
                if(tou == 0x02);            //If pad 2 is pressed
                {
                    PORTA = 0x09;
                    if(tou == 0x03);        //If pad 3 is pressed
                    {
                        PORTA = 0x11;
                        _delay_ms(1000);
                    }
                }
                else
                {
                    if(tou == 0x02);        //If pad 2 is pressed
                    {
                        PORTA = 0x09;
                        if(tou == 0x03);    //If pad 3 is pressed
                        {
                            PORTA = 0x11;
                            _delay_ms(1000);
                        }
                        else
                        {
                            if(tou == 0x03);//If pad 3 is pressed
                            {
                                PORTA = 0x11;
                                _delay_ms(1000);
                            }
                        }
                    }
                }

        }

    }
}`

Any help would be greatly appreciated.

Always give line information for compiler errors. In this case, it's easy to find, though (there aren't that many assignments): `i2c_start_wait(mpr03x=I2C_WRITE);`—what is this supposed to do? You're trying to assign a value to the literal `0x4A`. — mafso, Jun 27 '14 at 18:14

score 0 · Accepted Answer · answered Jun 27 '14 at 18:21

This will certainly cause problems:

    i2c_start_wait(mpr03x=I2C_WRITE);   //Set device address and write mode
                         ^

... because mpr03x is not a variable.

My assumption is that a back-tick isn't actually in your code on the last line, but I'll mention it anyway.

As someone else pointed out, i2c_stop; looks like a mistake.

error: lvalue required as left operand of assignment, error: void value not ignored as it ought to be

1 Answers1