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 /* Scheduler includes. */
30 #include "FreeRTOS.h"
31 #include "task.h"
32
33 /*-----------------------------------------------------------
34 * Implementation of functions defined in portable.h for the MSP430 port.
35 *----------------------------------------------------------*/
36
37 /* Constants required for hardware setup. The tick ISR runs off the ACLK,
38 * not the MCLK. */
39 #define portACLK_FREQUENCY_HZ ( ( TickType_t ) 32768 )
40 #define portINITIAL_CRITICAL_NESTING ( ( uint16_t ) 10 )
41 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x08 )
42
43 /* We require the address of the pxCurrentTCB variable, but don't want to know
44 * any details of its type. */
45 typedef void TCB_t;
46 extern volatile TCB_t * volatile pxCurrentTCB;
47
48 /* Each task maintains a count of the critical section nesting depth. Each
49 * time a critical section is entered the count is incremented. Each time a
50 * critical section is exited the count is decremented - with interrupts only
51 * being re-enabled if the count is zero.
52 *
53 * usCriticalNesting will get set to zero when the scheduler starts, but must
54 * not be initialised to zero as this will cause problems during the startup
55 * sequence. */
56 volatile uint16_t usCriticalNesting = portINITIAL_CRITICAL_NESTING;
57 /*-----------------------------------------------------------*/
58
59
60 /*
61 * Sets up the periodic ISR used for the RTOS tick. This uses timer 0, but
62 * could have alternatively used the watchdog timer or timer 1.
63 */
64 void vPortSetupTimerInterrupt( void );
65 /*-----------------------------------------------------------*/
66
67 /*
68 * Initialise the stack of a task to look exactly as if a call to
69 * portSAVE_CONTEXT had been called.
70 *
71 * See the header file portable.h.
72 */
pxPortInitialiseStack(StackType_t * pxTopOfStack,TaskFunction_t pxCode,void * pvParameters)73 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
74 TaskFunction_t pxCode,
75 void * pvParameters )
76 {
77 /*
78 * Place a few bytes of known values on the bottom of the stack.
79 * This is just useful for debugging and can be included if required.
80 *
81 * pxTopOfStack = ( StackType_t ) 0x1111;
82 * pxTopOfStack--;
83 * pxTopOfStack = ( StackType_t ) 0x2222;
84 * pxTopOfStack--;
85 * pxTopOfStack = ( StackType_t ) 0x3333;
86 * pxTopOfStack--;
87 */
88
89 /* The msp430 automatically pushes the PC then SR onto the stack before
90 * executing an ISR. We want the stack to look just as if this has happened
91 * so place a pointer to the start of the task on the stack first - followed
92 * by the flags we want the task to use when it starts up. */
93 *pxTopOfStack = ( StackType_t ) pxCode;
94 pxTopOfStack--;
95 *pxTopOfStack = portFLAGS_INT_ENABLED;
96 pxTopOfStack--;
97
98 /* Next the general purpose registers. */
99 *pxTopOfStack = ( StackType_t ) 0x4444;
100 pxTopOfStack--;
101 *pxTopOfStack = ( StackType_t ) 0x5555;
102 pxTopOfStack--;
103 *pxTopOfStack = ( StackType_t ) 0x6666;
104 pxTopOfStack--;
105 *pxTopOfStack = ( StackType_t ) 0x7777;
106 pxTopOfStack--;
107 *pxTopOfStack = ( StackType_t ) 0x8888;
108 pxTopOfStack--;
109 *pxTopOfStack = ( StackType_t ) 0x9999;
110 pxTopOfStack--;
111 *pxTopOfStack = ( StackType_t ) 0xaaaa;
112 pxTopOfStack--;
113 *pxTopOfStack = ( StackType_t ) 0xbbbb;
114 pxTopOfStack--;
115
116 /* When the task starts is will expect to find the function parameter in
117 * R15. */
118 *pxTopOfStack = ( StackType_t ) pvParameters;
119 pxTopOfStack--;
120
121 *pxTopOfStack = ( StackType_t ) 0xdddd;
122 pxTopOfStack--;
123 *pxTopOfStack = ( StackType_t ) 0xeeee;
124 pxTopOfStack--;
125 *pxTopOfStack = ( StackType_t ) 0xffff;
126 pxTopOfStack--;
127
128 /* A variable is used to keep track of the critical section nesting.
129 * This variable has to be stored as part of the task context and is
130 * initially set to zero. */
131 *pxTopOfStack = ( StackType_t ) portNO_CRITICAL_SECTION_NESTING;
132
133 /* Return a pointer to the top of the stack we have generated so this can
134 * be stored in the task control block for the task. */
135 return pxTopOfStack;
136 }
137 /*-----------------------------------------------------------*/
138
vPortEndScheduler(void)139 void vPortEndScheduler( void )
140 {
141 /* It is unlikely that the MSP430 port will get stopped. If required simply
142 * disable the tick interrupt here. */
143 }
144 /*-----------------------------------------------------------*/
145
146 /*
147 * Hardware initialisation to generate the RTOS tick. This uses timer 0
148 * but could alternatively use the watchdog timer or timer 1.
149 */
vPortSetupTimerInterrupt(void)150 void vPortSetupTimerInterrupt( void )
151 {
152 /* Ensure the timer is stopped. */
153 TACTL = 0;
154
155 /* Run the timer of the ACLK. */
156 TACTL = TASSEL_1;
157
158 /* Clear everything to start with. */
159 TACTL |= TACLR;
160
161 /* Set the compare match value according to the tick rate we want. */
162 TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;
163
164 /* Enable the interrupts. */
165 TACCTL0 = CCIE;
166
167 /* Start up clean. */
168 TACTL |= TACLR;
169
170 /* Up mode. */
171 TACTL |= MC_1;
172 }
173 /*-----------------------------------------------------------*/
174
