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124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup cpu
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* @{
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*
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* @file lpm_cpu.c
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* @brief low-power mode implementation for MSP430 MCUs
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*
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* @author Kévin Roussel <Kevin.Roussel@inria.fr>
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* @author Ludwig Ortmann <ludwig.ortmann@fu-berlin.de>
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* @author Thomas Eichinger <thomas.eichinger@fu-berlin.de>
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*
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* @}
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*/
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#include <stdio.h>
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#if (__GNUC__ >= 4) && (__GNUC_MINOR__ > 5)
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#include <intrinsics.h> // MSP430-gcc compiler instrinsics
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#endif
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#include "board.h"
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#include <msp430.h>
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#include "lpm.h"
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/* Initialise the MSP430 power-saving mechanisms. */
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void lpm_init(void)
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{
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// nothing to initialize on MSP430s: everything is done by fiddling
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// with 4 bits of the status register (SR).
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// just ensure MCU is fully up and running at start
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lpm_awake();
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}
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/* Change the current power-saving mode. */
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enum lpm_mode lpm_set(enum lpm_mode target)
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{
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enum lpm_mode last_mode = lpm_get();
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switch (target)
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{
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case LPM_ON:
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// fully running MCU
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__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
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break;
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case LPM_IDLE:
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// lightest mode => LPM0 mode of MSP430
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__bic_status_register(OSCOFF | SCG0 | SCG1);
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// only stops CPU block
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__bis_status_register(CPUOFF);
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break;
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case LPM_SLEEP:
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// mid-level mode => LPM1 mode of MSP430
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__bic_status_register(OSCOFF | SCG1);
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// stops CPU and master clock blocks
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__bis_status_register(CPUOFF | SCG0);
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break;
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case LPM_POWERDOWN:
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// deep-level mode => LPM3 mode of MSP430
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__bic_status_register(OSCOFF);
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// stops all blocks except auxiliary clock (timers)
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__bis_status_register(CPUOFF | SCG0 | SCG1);
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break;
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case LPM_OFF:
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// MCU totally down (LPM4), only RESET or NMI can resume execution
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__bis_status_register(CPUOFF | OSCOFF | SCG0 | SCG1); // all blocks off
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break;
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default:
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printf("ERROR: trying to set an invalid low-power mode!\n");
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printf(" Operation aborted.\n\n");
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}
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return last_mode;
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}
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#define LPM_MASK_SR (CPUOFF | OSCOFF | SCG0 | SCG1)
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/* Return the current LPM mode of the MSP430 MCU. */
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enum lpm_mode lpm_get(void)
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{
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enum lpm_mode current_mode = LPM_UNKNOWN;
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unsigned int current_sr = __read_status_register();
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switch (current_sr & LPM_MASK_SR) {
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case CPUOFF + OSCOFF + SCG0 + SCG1: // MSP430's LPM4
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current_mode = LPM_OFF;
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break;
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case CPUOFF + SCG0 + SCG1: // MSP430's LPM3
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case CPUOFF + SCG1: // MSP430's LPM2
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current_mode = LPM_POWERDOWN;
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break;
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case CPUOFF + SCG0: // MSP430's LPM1
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current_mode = LPM_SLEEP;
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break;
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case CPUOFF: // MSP430's LPM1
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current_mode = LPM_IDLE;
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break;
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case 0: // MSP430 active
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current_mode = LPM_ON;
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break;
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}
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return current_mode;
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}
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/* resume the MSP430 MCU */
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inline void lpm_awake(void)
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{
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// disable all power savings mechanisms
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__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
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}
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/* the following two functions have no actual role to play MSP430s */
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inline void lpm_begin_awake(void) { }
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inline void lpm_end_awake(void) { }
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