1 /*
2 * FreeRTOS Kernel V11.1.0
3 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
4 *
5 * SPDX-License-Identifier: MIT
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy of
8 * this software and associated documentation files (the "Software"), to deal in
9 * the Software without restriction, including without limitation the rights to
10 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
11 * the Software, and to permit persons to whom the Software is furnished to do so,
12 * subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in all
15 * copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
19 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
20 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
21 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
22 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23 *
24 * https://www.FreeRTOS.org
25 * https://github.com/FreeRTOS
26 *
27 */
28
29 /*
30 Changes from V3.0.0
31 + ISRcode is pulled inline and portTICKisr() is therefore
32 deleted from this file.
33
34 + Prescaler logic for Timer1 added to allow for a wider
35 range of TickRates.
36
37 Changes from V3.0.1
38 */
39
40 #include <FreeRTOS.h>
41 #include <task.h>
42
43 /* IO port constants. */
44 #define portBIT_SET (1)
45 #define portBIT_CLEAR (0)
46
47 /*
48 * Hardware setup for the tick.
49 * We use a compare match on timer1. Depending on MPU-frequency
50 * and requested tickrate, a prescaled value with a matching
51 * prescaler are determined.
52 */
53 #define portTIMER_COMPARE_BASE ((APROCFREQ/4)/configTICK_RATE_HZ)
54
55 #if portTIMER_COMPARE_BASE < 0x10000
56 #define portTIMER_COMPARE_VALUE (portTIMER_COMPARE_BASE)
57 #define portTIMER_COMPARE_PS1 (portBIT_CLEAR)
58 #define portTIMER_COMPARE_PS0 (portBIT_CLEAR)
59 #elif portTIMER_COMPARE_BASE < 0x20000
60 #define portTIMER_COMPARE_VALUE (portTIMER_COMPARE_BASE / 2)
61 #define portTIMER_COMPARE_PS1 (portBIT_CLEAR)
62 #define portTIMER_COMPARE_PS0 (portBIT_SET)
63 #elif portTIMER_COMPARE_BASE < 0x40000
64 #define portTIMER_COMPARE_VALUE (portTIMER_COMPARE_BASE / 4)
65 #define portTIMER_COMPARE_PS1 (portBIT_SET)
66 #define portTIMER_COMPARE_PS0 (portBIT_CLEAR)
67 #elif portTIMER_COMPARE_BASE < 0x80000
68 #define portTIMER_COMPARE_VALUE (portTIMER_COMPARE_BASE / 8)
69 #define portTIMER_COMPARE_PS1 (portBIT_SET)
70 #define portTIMER_COMPARE_PS0 (portBIT_SET)
71 #else
72 #error "TickRate out of range"
73 #endif
74
75 /*-----------------------------------------------------------*/
76
77 /*
78 * Setup a timer for a regular tick.
79 */
portSetupTick(void)80 void portSetupTick( void )
81 {
82 /*
83 * Interrupts are disabled when this function is called.
84 */
85
86 /*
87 * Setup CCP1
88 * Provide the tick interrupt using a compare match on timer1.
89 */
90
91 /*
92 * Set the compare match value.
93 */
94 CCPR1H = ( uint8_t ) ( ( portTIMER_COMPARE_VALUE >> 8 ) & 0xff );
95 CCPR1L = ( uint8_t ) ( portTIMER_COMPARE_VALUE & 0xff );
96
97 /*
98 * Set Compare Special Event Trigger Mode
99 */
100 bCCP1M3 = portBIT_SET;
101 bCCP1M2 = portBIT_CLEAR;
102 bCCP1M1 = portBIT_SET;
103 bCCP1M0 = portBIT_SET;
104
105 /*
106 * Enable CCP1 interrupt
107 */
108 bCCP1IE = portBIT_SET;
109
110 /*
111 * We are only going to use the global interrupt bit, so disable
112 * interruptpriorities and enable peripheral interrupts.
113 */
114 bIPEN = portBIT_CLEAR;
115 bPEIE = portBIT_SET;
116
117 /*
118 * Set up timer1
119 * It will produce the system tick.
120 */
121
122 /*
123 * Clear the time count
124 */
125 TMR1H = ( uint8_t ) 0x00;
126 TMR1L = ( uint8_t ) 0x00;
127
128 /*
129 * Setup the timer
130 */
131 bRD16 = portBIT_SET; // 16-bit
132 bT1CKPS1 = portTIMER_COMPARE_PS1; // prescaler
133 bT1CKPS0 = portTIMER_COMPARE_PS0; // prescaler
134 bT1OSCEN = portBIT_SET; // Oscillator enable
135 bT1SYNC = portBIT_SET; // No external clock sync
136 bTMR1CS = portBIT_CLEAR; // Internal clock
137
138 bTMR1ON = portBIT_SET; // Start timer1
139 }
140
