vos/ambiq-hal-sys/ambiq-sparkfun-sdk/boards/apollo1_evb/examples/clkout/src/clkout.c

//*****************************************************************************
//
//! @file clkout.c
//!
//! @brief Enables a clock source to clkout and then tracks it on an LED array.
//!
//! This example enables the LFRC to a clkout pin then uses GPIO polling to
//! track its rising edge and toggle an LED at 1 hertz.
//
//*****************************************************************************

//*****************************************************************************
//
// Copyright (c) 2020, Ambiq Micro
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from this
// software without specific prior written permission.
//
// Third party software included in this distribution is subject to the
// additional license terms as defined in the /docs/licenses directory.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// This is part of revision 2.4.2 of the AmbiqSuite Development Package.
//
//*****************************************************************************

#include "am_mcu_apollo.h"
#include "am_bsp.h"
#include "am_util.h"

//*****************************************************************************
//
// Macro definitions
//
//*****************************************************************************
#define RISING_EDGE_COUNT   500     // Turn 500 Hz (LFRC/2) clkout into 1 Hz blinky

//*****************************************************************************
//
// Main function.
//
//*****************************************************************************
int
main(void)
{
    int32_t iRisingCount, iLEDcount;
    bool bNewClkout, bOldClkout;

    //
    // Set the clock frequency.
    //
    am_hal_clkgen_sysclk_select(AM_HAL_CLKGEN_SYSCLK_MAX);

    //
    // Set the default cache configuration
    //
    am_hal_cachectrl_enable(&am_hal_cachectrl_defaults);

    //
    // Configure the board for low power operation.
    //
    am_bsp_low_power_init();

    //
    // Initialize the printf interface for ITM/SWO output.
    //
    am_util_stdio_printf_init((am_util_stdio_print_char_t) am_bsp_itm_string_print);

    //
    // Initialize the SWO GPIO pin
    //
    am_bsp_pin_enable(ITM_SWO);

    //
    // Enable the ITM.
    //
    am_hal_itm_enable();

    //
    // Enable debug printf messages using ITM on SWO pin
    //
    am_bsp_debug_printf_enable();

    //
    // Clear the terminal and print the banner.
    //
    am_util_stdio_terminal_clear();
    am_util_stdio_printf("CLKOUT to LED Example\n");
    am_util_stdio_printf("\tWalks the board LEDs about once a second based on the CLKOUT "
                         "signal.\n");

    //
    // We are done printing. Disable debug printf messages on ITM.
    //
    am_bsp_debug_printf_disable();

    //
    // Clear the LED.
    //
    am_devices_led_array_init(am_bsp_psLEDs, AM_BSP_NUM_LEDS);

    //
    // Enable the LFRC.
    //
    am_hal_clkgen_osc_start(AM_HAL_CLKGEN_OSC_LFRC);

    //
    // Enable the clockout to the desired pin.
    // And make it readable on the pin with AM_HAL_GPIO_INPEN
    //
    am_hal_gpio_pin_config(AM_BSP_GPIO_CLKOUT_PIN,
                           (AM_BSP_GPIO_CFG_CLKOUT_PIN | AM_HAL_GPIO_INPEN));

    //
    // Initialize clkgen to output the selected clock.
    //
    am_hal_clkgen_clkout_enable(AM_HAL_CLKGEN_CLKOUT_CKSEL_LFRC_DIV2);

    //
    // Initialize LED 0 to on
    //
    am_devices_led_toggle(am_bsp_psLEDs, 0);
    iLEDcount = 1;      // LED 1 is next

    //
    // Initialize loop variables
    //
    iRisingCount = RISING_EDGE_COUNT;
    bOldClkout = false;

    //
    // Loop forever tracking the rising edge of CLKOUT.
    //
    while (1)
    {
        //
        // Grab new clock output value and look for a change.
        //
        bNewClkout = am_hal_gpio_input_bit_read(AM_BSP_GPIO_CLKOUT_PIN);

        //
        // Look for any change.
        //
        if ( bOldClkout != bNewClkout )
        {
            //
            // OK a change occurred.
            //
            bOldClkout = bNewClkout;

            //
            //  Was it rising or falling.
            //
            if ( bNewClkout )
            {
                //
                // It was rising so count them until time to act.
                //
                if (--iRisingCount < 0)
                {
                    //
                    // Act on the time out (walk the 4 LEDs)
                    //
                    am_devices_led_off(am_bsp_psLEDs, 0);
                    am_devices_led_off(am_bsp_psLEDs, 1);
                    am_devices_led_off(am_bsp_psLEDs, 2);
                    am_devices_led_off(am_bsp_psLEDs, 3);
                    am_devices_led_off(am_bsp_psLEDs, 4);
                    am_devices_led_on(am_bsp_psLEDs, iLEDcount);
                    iLEDcount++;
                    iLEDcount %= 5;

                    //
                    // Reset the rising edge count.
                    //
                    iRisingCount = RISING_EDGE_COUNT;
                }
            }
        }

    }

}