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 prvSetupTimerInterrupt( 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, TaskFunction_t pxCode, void *pvParameters )
74 {
75 /*
76 Place a few bytes of known values on the bottom of the stack.
77 This is just useful for debugging and can be included if required.
78
79 *pxTopOfStack = ( StackType_t ) 0x1111;
80 pxTopOfStack--;
81 *pxTopOfStack = ( StackType_t ) 0x2222;
82 pxTopOfStack--;
83 *pxTopOfStack = ( StackType_t ) 0x3333;
84 pxTopOfStack--;
85 */
86
87 /* The msp430 automatically pushes the PC then SR onto the stack before
88 executing an ISR. We want the stack to look just as if this has happened
89 so place a pointer to the start of the task on the stack first - followed
90 by the flags we want the task to use when it starts up. */
91 *pxTopOfStack = ( StackType_t ) pxCode;
92 pxTopOfStack--;
93 *pxTopOfStack = portFLAGS_INT_ENABLED;
94 pxTopOfStack--;
95
96 /* Next the general purpose registers. */
97 *pxTopOfStack = ( StackType_t ) 0x4444;
98 pxTopOfStack--;
99 *pxTopOfStack = ( StackType_t ) 0x5555;
100 pxTopOfStack--;
101 *pxTopOfStack = ( StackType_t ) 0x6666;
102 pxTopOfStack--;
103 *pxTopOfStack = ( StackType_t ) 0x7777;
104 pxTopOfStack--;
105 *pxTopOfStack = ( StackType_t ) 0x8888;
106 pxTopOfStack--;
107 *pxTopOfStack = ( StackType_t ) 0x9999;
108 pxTopOfStack--;
109 *pxTopOfStack = ( StackType_t ) 0xaaaa;
110 pxTopOfStack--;
111 *pxTopOfStack = ( StackType_t ) 0xbbbb;
112 pxTopOfStack--;
113 *pxTopOfStack = ( StackType_t ) 0xcccc;
114 pxTopOfStack--;
115 *pxTopOfStack = ( StackType_t ) 0xdddd;
116 pxTopOfStack--;
117 *pxTopOfStack = ( StackType_t ) 0xeeee;
118 pxTopOfStack--;
119
120 /* When the task starts is will expect to find the function parameter in
121 R15. */
122 *pxTopOfStack = ( StackType_t ) pvParameters;
123 pxTopOfStack--;
124
125 /* A variable is used to keep track of the critical section nesting.
126 This variable has to be stored as part of the task context and is
127 initially set to zero. */
128 *pxTopOfStack = ( StackType_t ) portNO_CRITICAL_SECTION_NESTING;
129
130 /* Return a pointer to the top of the stack we have generated so this can
131 be stored in the task control block for the task. */
132 return pxTopOfStack;
133 }
134 /*-----------------------------------------------------------*/
135
vPortEndScheduler(void)136 void vPortEndScheduler( void )
137 {
138 /* It is unlikely that the MSP430 port will get stopped. If required simply
139 disable the tick interrupt here. */
140 }
141 /*-----------------------------------------------------------*/
142
143 /*
144 * Hardware initialisation to generate the RTOS tick. This uses timer 0
145 * but could alternatively use the watchdog timer or timer 1.
146 */
prvSetupTimerInterrupt(void)147 void prvSetupTimerInterrupt( void )
148 {
149 /* Ensure the timer is stopped. */
150 TACTL = 0;
151
152 /* Run the timer of the ACLK. */
153 TACTL = TASSEL_1;
154
155 /* Clear everything to start with. */
156 TACTL |= TACLR;
157
158 /* Set the compare match value according to the tick rate we want. */
159 TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;
160
161 /* Enable the interrupts. */
162 TACCTL0 = CCIE;
163
164 /* Start up clean. */
165 TACTL |= TACLR;
166
167 /* Up mode. */
168 TACTL |= MC_1;
169 }
170 /*-----------------------------------------------------------*/
171
172
173
174
