cpu.c
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/*
* Copyright (C) 2014 Loci Controls Inc.
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu_cc2538
* @{
*
* @file
* @brief Implementation of the CPU initialization
*
* @author Ian Martin <ian@locicontrols.com>
* @}
*/
#include <assert.h>
#include "cpu.h"
#define BIT(n) ( 1UL << (n) )
/* Select CLOCK_CTRL register bit masks: */
#define OSC32K BIT(24) /**< 32-kHz clock oscillator selection */
#define OSC_PD BIT(17) /**< Oscillator power-down */
#define OSC BIT(16) /**< System clock oscillator selection */
/* CLOCK_CTRL register field offsets: */
#define IO_DIV_SHIFT 8
#define SYS_DIV_SHIFT 0
#define CLOCK_STA_MASK ( OSC32K | OSC )
static void cpu_clock_init(void);
/**
* @brief Initialize the CPU, set IRQ priorities
*/
void cpu_init(void)
{
/* initialize the Cortex-M core */
cortexm_init();
/* Enable the CC2538's more compact alternate interrupt mapping */
SYS_CTRL->I_MAP = 1;
/* initialize the clock system */
cpu_clock_init();
/* initialize the GPIO controller */
cc2538_gpio_init();
}
/**
* @brief Configure the controllers clock system
*/
static void cpu_clock_init(void)
{
const uint32_t CLOCK_CTRL_VALUE =
OSC_PD /**< Power down the oscillator not selected by OSC bit (hardware-controlled when selected). */
| (1 << IO_DIV_SHIFT) /**< 16 MHz IO_DIV */
| (1 << SYS_DIV_SHIFT) /**< 16 MHz SYS_DIV */
#if !SYS_CTRL_OSC32K_USE_XTAL
| OSC32K /**< Use internal RC oscillator. */
#endif
;
#if SYS_CTRL_OSC32K_USE_XTAL
/* Set the XOSC32K_Q pads to analog for the external crystal: */
gpio_software_control(GPIO_PD6);
gpio_dir_input(GPIO_PD6);
IOC_PXX_OVER[GPIO_PD6] = IOC_OVERRIDE_ANA;
gpio_software_control(GPIO_PD7);
gpio_dir_input(GPIO_PD7);
IOC_PXX_OVER[GPIO_PD7] = IOC_OVERRIDE_ANA;
#endif
/* Configure the clock settings: */
SYS_CTRL->cc2538_sys_ctrl_clk_ctrl.CLOCK_CTRL = CLOCK_CTRL_VALUE;
/* Wait for the new clock settings to take effect: */
while ((SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STA ^ CLOCK_CTRL_VALUE) & CLOCK_STA_MASK);
#if SYS_CTRL_OSC32K_USE_XTAL
/* Wait for the 32-kHz crystal oscillator to stabilize: */
while ( SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K);
while (!SYS_CTRL->cc2538_sys_ctrl_clk_sta.CLOCK_STAbits.SYNC_32K);
#endif
}