GPIOA ODR ^= 0x0001: Toggling the First Bit in C

The line of code 'gpioa->odr ^= 0x0001' toggles the value of the first bit (bit 0) of the output data register (ODR) of GPIO port A. The '^=' operator is the XOR assignment operator, which performs a bitwise XOR operation between the current value of the ODR and the value 0x0001, storing the result back in the ODR.

This means:

• If the first bit of the ODR was previously 0, it will be set to 1.
• If it was previously 1, it will be set to 0.

This technique is commonly used to toggle an LED connected to the first pin of GPIO port A, effectively switching it on and off.