/**
* \brief Multiplex group of pins to the given alternate function
*
* Mux the pin or group of pins to the given alternate function. Note that a
* number of pins may be set but only with a single AF number. This is useful
* when one or more of a peripheral's pins are assigned to the same alternate
* function.
*
* Because AF0 is not used on the LM4F, passing 0 as the alt_func_num parameter
* will disable the alternate function of the given pins.
*
* @param[in] gpioport GPIO block register address base @ref gpio_reg_base
* @param[in] alt_func_num Pin alternate function number or 0 to disable the
* alternate function multiplexing.
* @param[in] gpios @ref gpio_pin_id. Any combination of pins may be specified
* by OR'ing then together
*/
void gpio_set_af(uint32_t gpioport, uint8_t alt_func_num, uint8_t gpios)
{
uint32_t pctl32;
uint8_t pin_mask;
int i;
/* Did we mean to disable the alternate function? */
if (alt_func_num == 0) {
GPIO_AFSEL(gpioport) &= ~gpios;
return;
}
/* Enable the alternate function */
GPIO_AFSEL(gpioport) |= gpios;
/* Alternate functions are digital */
GPIO_DEN(gpioport) |= gpios;
/* Now take care of the actual multiplexing */
pctl32 = GPIO_PCTL(gpioport);
for (i = 0; i < 8; i++) {
pin_mask = (1 << i);
if (!(gpios & pin_mask)) {
continue;
}
pctl32 &= ~PCTL_MASK(i);
pctl32 |= PCTL_AF(i, (alt_func_num & 0xf));
}
GPIO_PCTL(gpioport) = pctl32;
}
static void uart_setup(void)
{
u32 pins;
/* Enable GPIOA in run mode. */
periph_clock_enable(RCC_GPIOA);
/* Configure PA0 and PA1 as alternate function pins */
pins = GPIO0 | GPIO1;
GPIO_AFSEL(GPIOA) |= pins;
GPIO_DEN(GPIOA) |= pins;
/* PA0 and PA1 are muxed to UART0 during power on, by default */
/* Enable the UART clock */
periph_clock_enable(RCC_UART0);
/* We need a brief delay before we can access UART config registers */
__asm__("nop");
/* Disable the UART while we mess with its setings */
uart_disable(UART0);
/* Configure the UART clock source as precision internal oscillator */
uart_clock_from_piosc(UART0);
/* Set communication parameters */
uart_set_baudrate(UART0, 921600);
uart_set_databits(UART0, 8);
uart_set_parity(UART0, UART_PARITY_NONE);
uart_set_stopbits(UART0, 1);
/* Now that we're done messing with the settings, enable the UART */
uart_enable(UART0);
}
