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//*****************************************************************************
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//
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//! @file pwm_gen.c
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//!
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//! @brief Breathing LED example.
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//!
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//! This example shows one way to vary the brightness of an LED using timers in
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//! PWM mode.
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//
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//*****************************************************************************
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//*****************************************************************************
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//
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// Copyright (c) 2020, Ambiq Micro
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its
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// contributors may be used to endorse or promote products derived from this
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// software without specific prior written permission.
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//
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// Third party software included in this distribution is subject to the
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// additional license terms as defined in the /docs/licenses directory.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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// This is part of revision 2.4.2 of the AmbiqSuite Development Package.
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//
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//*****************************************************************************
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#include "am_mcu_apollo.h"
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#include "am_bsp.h"
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#include "am_util.h"
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//*****************************************************************************
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//
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// LED brightness profile
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//
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//*****************************************************************************
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volatile uint32_t g_ui32Index = 0;
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const uint32_t g_pui32Brightness[64] =
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{
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1, 1, 1, 2, 3, 4, 6, 8,
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10, 12, 14, 17, 20, 23, 25, 28,
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31, 35, 38, 40, 43, 46, 49, 51,
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53, 55, 57, 59, 60, 61, 62, 62,
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63, 62, 62, 61, 60, 59, 57, 55,
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53, 51, 49, 46, 43, 40, 38, 35,
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32, 28, 25, 23, 20, 17, 14, 12,
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10, 8, 6, 4, 3, 2, 1, 1
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};
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//*****************************************************************************
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//
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// Timer Interrupt Serive Routine (ISR)
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//
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//*****************************************************************************
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void
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am_ctimer_isr(void)
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{
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//
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// Clear the interrupt that got us here.
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//
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am_hal_ctimer_int_clear(AM_BSP_PWM_LED_TIMER_INT);
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//
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// Now set new PWM half-period for the LED.
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//
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am_hal_ctimer_period_set(AM_BSP_PWM_LED_TIMER, AM_BSP_PWM_LED_TIMER_SEG,
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64, g_pui32Brightness[g_ui32Index]);
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//
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// Set up the LED duty cycle for the next pulse.
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//
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g_ui32Index = (g_ui32Index + 1) % 64;
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}
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//*****************************************************************************
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//
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// Main function.
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//
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//*****************************************************************************
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int
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main(void)
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{
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//
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// Set the clock frequency.
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//
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am_hal_clkgen_sysclk_select(AM_HAL_CLKGEN_SYSCLK_MAX);
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//
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// Set the default cache configuration
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//
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am_hal_cachectrl_enable(&am_hal_cachectrl_defaults);
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//
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// Configure the board for low power operation.
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//
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am_bsp_low_power_init();
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//
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// Among other things, am_bsp_low_power_init() stops the XT oscillator,
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// which is needed for this example.
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//
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am_hal_clkgen_osc_start(AM_HAL_CLKGEN_OSC_XT);
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//
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// Configure the pins for this example.
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//
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am_bsp_pin_enable(PWM_LED);
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//
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// Initialize the printf interface for ITM/SWO output.
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//
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am_util_stdio_printf_init((am_util_stdio_print_char_t) am_bsp_itm_string_print);
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//
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// Initialize the SWO GPIO pin
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//
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am_bsp_pin_enable(ITM_SWO);
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//
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// Enable the ITM.
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//
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am_hal_itm_enable();
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//
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// Enable debug printf messages using ITM on SWO pin
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//
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am_bsp_debug_printf_enable();
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//
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// Clear the terminal and print the banner.
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//
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am_util_stdio_terminal_clear();
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am_util_stdio_printf("PWM Example\n\n");
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am_util_delay_ms(10);
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//
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// We are done printing. Disable debug printf messages on ITM.
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//
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am_bsp_debug_printf_disable();
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//
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// Configure a timer to drive the LED.
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//
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am_hal_ctimer_config_single(AM_BSP_PWM_LED_TIMER, AM_BSP_PWM_LED_TIMER_SEG,
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(AM_HAL_CTIMER_FN_PWM_REPEAT |
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AM_HAL_CTIMER_XT_2_048KHZ |
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AM_HAL_CTIMER_INT_ENABLE |
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AM_HAL_CTIMER_PIN_ENABLE));
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//
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// Set up initial timer period.
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//
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am_hal_ctimer_period_set(AM_BSP_PWM_LED_TIMER, AM_BSP_PWM_LED_TIMER_SEG,
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64, 32);
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//
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// Enable interrupts for the Timer we are using on this board.
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//
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am_hal_ctimer_int_enable(AM_BSP_PWM_LED_TIMER_INT);
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am_hal_interrupt_enable(AM_HAL_INTERRUPT_CTIMER);
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am_hal_interrupt_master_enable();
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//
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// Start the timer.
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//
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am_hal_ctimer_start(AM_BSP_PWM_LED_TIMER, AM_BSP_PWM_LED_TIMER_SEG);
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//
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// Sleep forever while waiting for an interrupt.
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//
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while (1)
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{
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//
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// Go to Deep Sleep.
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//
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am_hal_sysctrl_sleep(AM_HAL_SYSCTRL_SLEEP_DEEP);
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}
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}
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