3. Write C code that enables the clock of SYSCFG, GPIOA and GPIOB ports. Enable corresponding GPIOA pin 0 for input (the joystick center pushbutton) and GPIOB pin 2 for output, push-pull (red LED). 4. Find Table 34 in section 10.2.11 that shows info about the SYSCRG register group. Write O instructions to configure the SYSCFG external interrupt configuration register (SYSCFGEXTlCR) to map the GPIOA pin 0 to the external interrupt input ine 0. 5. 6. Write C instructions to select a signal change that will trigger EXTI 0. The signal can be a rising edge, a falling edge or both. This is configured by the EXTI rising edge trigger selection register EXTI RTSR1 or EXTI RTSR2) and the Falling edge trigger selection register (EXTI FTSR1 or EXTI FTSR2) 7. Write C instructions to set the Oh bit in EXTI interrupt mask register (EXTI IMR1 or EXTI IMR2) and EXTI event mask register (EXTI EMR1 or EXTI EMR2) to enable the EXTI interrupt and event for input line 0 Write C instructions to configure the enable and mask bit that controls the NVIC interrupt channel mapping to EXTI 0 8. 9. Write an interrupt handler for EXTI 0 that turns the red LED on. The EXTI pending register (EXTI PRI or EXTI PR2) records the source of the interrupt. The function name of the interrupt handler is given by the startup assembly file startup_stm 321476x.s. For example, the handler for EXTI 0 is called EXTIO IRHanderO 10. In the interrupt handler, the corresponding pending bit needs to be cleared by your software for future interrupt. Surprisingly, writing it to 1 clears a pending bit