How to use JTAG port as a normal I/O port in AVR microcontroller-EEWORLD

method 1:

Modify the fuse bit to disable JTAG. (Disadvantage: JTAG cannot be used after disabling, unless it is enabled again using ISP)

Method 2:

To disable JTAG in your program, call the following function:

inline void JTAG_Disable(void)
{
    unsigned char temp = 0;
    temp = MCUCSR | (1 << JTD);
    MCUCSR = temp;
    MCUCSR = temp;
}

If you need to restart, call the following function:

inline void JTAG_Enable(void)
{
    unsigned char temp = 0;
    temp = MCUCSR & (~(1 << JTD));
    MCUCSR = temp;
    MCUCSR = temp;
}

Note: If you disable JTAG in the program and do not re-enable it, JTAG will not be able to connect. There are two solutions.

(Method 1): Press and hold the reset button and then connect.

(Method 2): In the dialog box that pops up when the connection fails, select the following:

Click "Retry" again to connect.

The premise of this method is that the JTAG ICE must be standard, and many shoddy ones will not work.

Reference address：How to use JTAG port as a normal I/O port in AVR microcontroller

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