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/*
* Copyright (C) 2014 Freie Universität Berlin
*
* 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
* @{
*
* @file lpm_cpu.c
* @brief low-power mode implementation for MSP430 MCUs
*
* @author Kévin Roussel <Kevin.Roussel@inria.fr>
* @author Ludwig Ortmann <ludwig.ortmann@fu-berlin.de>
* @author Thomas Eichinger <thomas.eichinger@fu-berlin.de>
*
* @}
*/
#include <stdio.h>
#if (__GNUC__ >= 4) && (__GNUC_MINOR__ > 5)
#include <intrinsics.h> // MSP430-gcc compiler instrinsics
#endif
#include "board.h"
#include <msp430.h>
#include "lpm.h"
/* Initialise the MSP430 power-saving mechanisms. */
void lpm_init(void)
{
// nothing to initialize on MSP430s: everything is done by fiddling
// with 4 bits of the status register (SR).
// just ensure MCU is fully up and running at start
lpm_awake();
}
/* Change the current power-saving mode. */
enum lpm_mode lpm_set(enum lpm_mode target)
{
enum lpm_mode last_mode = lpm_get();
switch (target)
{
case LPM_ON:
// fully running MCU
__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
break;
case LPM_IDLE:
// lightest mode => LPM0 mode of MSP430
__bic_status_register(OSCOFF | SCG0 | SCG1);
// only stops CPU block
__bis_status_register(CPUOFF);
break;
case LPM_SLEEP:
// mid-level mode => LPM1 mode of MSP430
__bic_status_register(OSCOFF | SCG1);
// stops CPU and master clock blocks
__bis_status_register(CPUOFF | SCG0);
break;
case LPM_POWERDOWN:
// deep-level mode => LPM3 mode of MSP430
__bic_status_register(OSCOFF);
// stops all blocks except auxiliary clock (timers)
__bis_status_register(CPUOFF | SCG0 | SCG1);
break;
case LPM_OFF:
// MCU totally down (LPM4), only RESET or NMI can resume execution
__bis_status_register(CPUOFF | OSCOFF | SCG0 | SCG1); // all blocks off
break;
default:
printf("ERROR: trying to set an invalid low-power mode!\n");
printf(" Operation aborted.\n\n");
}
return last_mode;
}
#define LPM_MASK_SR (CPUOFF | OSCOFF | SCG0 | SCG1)
/* Return the current LPM mode of the MSP430 MCU. */
enum lpm_mode lpm_get(void)
{
enum lpm_mode current_mode = LPM_UNKNOWN;
unsigned int current_sr = __read_status_register();
switch (current_sr & LPM_MASK_SR) {
case CPUOFF + OSCOFF + SCG0 + SCG1: // MSP430's LPM4
current_mode = LPM_OFF;
break;
case CPUOFF + SCG0 + SCG1: // MSP430's LPM3
case CPUOFF + SCG1: // MSP430's LPM2
current_mode = LPM_POWERDOWN;
break;
case CPUOFF + SCG0: // MSP430's LPM1
current_mode = LPM_SLEEP;
break;
case CPUOFF: // MSP430's LPM1
current_mode = LPM_IDLE;
break;
case 0: // MSP430 active
current_mode = LPM_ON;
break;
}
return current_mode;
}
/* resume the MSP430 MCU */
inline void lpm_awake(void)
{
// disable all power savings mechanisms
__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
}
/* the following two functions have no actual role to play MSP430s */
inline void lpm_begin_awake(void) { }
inline void lpm_end_awake(void) { }