Solution

Solution to the assignment.

Q1 It takes longer to make the copy, so the chance of interrupting this process increases.

Q2

// Critical section start
uint32_t m = __get_PRIMASK();
__disable_irq();             

// Copy the global buffer
for(uint32_t i=0; i<sizeof(global_buffer); i++)
{
    local_buffer[i] = global_buffer[i];

    // Artificial delay to increase the chance of interrupting this
    // critical section
    for(uint32_t d=0; d<200000; d++)
    {}                
}

__set_PRIMASK(m);
// Critical section end   

Q3 The first click copies the buffer and prints it. Printing means it is written into the transmit buffer of the LPUART, which is transmitted interrupt based. If there is a second SW3 click, which disables all interrupts, the transmission of UART characters will temporarily stop.