1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
/****************************************************************************
* arch/avr/src/atmega/atmega_timerisr.c
*
* Copyright (C) 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* 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 OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <time.h>
#include <debug.h>
#include <nuttx/arch.h>
#include <arch/board/board.h>
#include <avr/io.h>
#include "up_arch.h"
#include "atmega_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/* The CPU frequency is given by BOARD_CPU_CLOCK (defined in board.h). The
* desired interrupt frequency is given by CONFIG_MSEC_PER_TICK. An unscaled
* ideal match is given by:
*
* CLOCK = CPU_CLOCK / DIVISOR # CPU clocks/sec
* MATCH = CLOCK / CLOCKS_PER_SEC # CPU clocks/timer tick
* MATCH = CPU_CLOCK / DIVISOR / CLOCKS_PER_SEC # CPU clocks/timer tick
*
* But we only have 16-bits of accuracy so we need to pick the smallest
* divisor using the following brute force calculation:
*/
#define MATCH1 (( BOARD_CPU_CLOCK + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC)
#define MATCH8 ((((BOARD_CPU_CLOCK + 4) / 8) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC)
#define MATCH64 ((((BOARD_CPU_CLOCK + 8) / 64) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC)
#define MATCH256 ((((BOARD_CPU_CLOCK + 128) / 256) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC)
#define MATCH1024 ((((BOARD_CPU_CLOCK + 512) / 1024) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC)
#if MATCH1 <= 65536
# define MATCH (MATCH1-1)
# define PRESCALE 1
#elif MATCH8 <= 65536
# define MATCH (MATCH8-1)
# define PRESCALE 2
#elif MATCH64 <= 65536
# define MATCH (MATCH64-1)
# define PRESCALE 3
#elif MATCH256 <= 65536
# define MATCH (MATCH256-1)
# define PRESCALE 4
#elif MATCH1024 <= 65536
# define MATCH (MATCH1024-1)
# define PRESCALE 5
#else
# error "Cannot represent this timer frequency"
#endif
/*
* Eg. CPU_CLOCK = 8MHz, CLOCKS_PER_SEC = 100
*
* MATCH1 ((8000000 + 50) / 100) = 80,000 FREQ=100.0Hz
* MATCH8 ((1000000 + 50) / 100) = 10,000 FREQ=100.0Hz <-- this one
* MATCH64 (( 125000 + 50) / 100) = 1,250 FREQ=100.0Hz
* MATCH256 (( 31250 + 50) / 100) = 313 FREQ=99.8Hz
* MATCH1024 (( 7804 + 50) / 100) = 78 FREQ=100.1Hz
*/
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Function: up_timerisr
*
* Description:
* The timer ISR will perform a variety of services for various portions
* of the systems.
*
****************************************************************************/
int up_timerisr(int irq, uint32_t *regs)
{
/* Process timer interrupt */
sched_process_timer();
return 0;
}
/****************************************************************************
* Function: up_timerinit
*
* Description:
* This function is called during start-up to initialize the timer
* interrupt. NOTE: This function depends on setup of OSC32 by
* up_clkinitialize().
*
****************************************************************************/
void up_timerinit(void)
{
/* Setup timer 1 compare match A to generate a tick interrupt.
*
* First, setup the match value for compare match A.
*/
OCR1AH = (uint8_t)((uint16_t)MATCH >> 8);
OCR1AL = (uint8_t)((uint16_t)MATCH & 0xff);
/* Setup clock source and compare match behaviour. */
TCCR1A = 0x08 | PRESCALE;
/* Attach the timer interrupt vector */
(void)irq_attach(AT90USB_IRQ_T2COMPA, (xcpt_t)up_timerisr);
/* Enable the interrupt on compare match A */
TIMSK1 |= 0x10;
}
|
