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
|
Microsoft's Azure RTOS ThreadX for Cortex-M3
Using the Green Hills Software Tools
1. Open the ThreadX Project Workspace
In order to build the ThreadX library and the ThreadX demonstration first load
the Azure RTOS Workspace azure_rtos_workspace.gpj, which is located inside the
"example_build" directory.
2. Building the ThreadX run-time Library
Building the ThreadX library is easy; simply select the MULTI project file
tx.gpj and then select the build button. You should now observe the
compilation and assembly of the ThreadX library. This project build produces
the ThreadX library file tx.a.
3. Demonstration System
The ThreadX demonstration is designed to execute under the MULTI environment
on the Green Hills Cortex-M3 simulator. The instructions that follow describe
how to get the ThreadX evaluation running under the MULTI Cortex-M3 simulation
environment.
Building the demonstration is easy; simply select the MULTI project file
sample_threadx.gpj. At this point, select the "Project Build" button and observe
the compilation, assembly, and linkage of the ThreadX demonstration application.
After the demonstration is built, invoke the MULTI ARM simulator by selecting
the simulator connection from within the sample_threadx.con connection file.
Once connected to the simulator, select the "Debug" button. You should now
observe the main function of sample_threadx.c.
You are now ready to execute the ThreadX demonstration system. Select
breakpoints and data watches to observe the execution of the sample_threadx.c
application.
4. EventAnalyzer Demonstration
To build a demonstration system that also logs events for the MULTI EventAnalyzer,
perform the same steps as the regular demo, except build the ThreadX library with
txe.gpj file and use the sample_threadx_el.gpj build file to build the demonstration.
The resulting image will log all system events, which can then be displayed by the
MULTI EventAnalyzer.
5. System Initialization
The system entry point using the Green Hills tools is at the label _start.
This is defined within the crt0.arm file supplied by Green Hills. In addition,
this is where all static and global preset C variable initialization
processing is called from.
After the Green Hills startup function returns, ThreadX initialization is
called. The main initialization function is _tx_initialize_low_level and
is located in the file tx_initialize_low_level.arm. This function is responsible
for setting up various system data structures, interrupt vectors, and the
periodic timer interrupt source of ThreadX.
In addition, _tx_initialize_low_level determines where the first available
RAM memory address is located. This address is supplied to tx_application_define.
By default, the first available RAM memory address is assumed to start at the
beginning of the ThreadX section .free_mem. If changes are made to the
sample_threadx.ld file, the .free_mem section should remain the last allocated
section in the main RAM area. The starting address of this section is passed
to tx_application_define.
6. Register Usage and Stack Frames
The following defines the saved context stack frames for context switches
that occur as a result of interrupt handling or from thread-level API calls.
All suspended threads have the same stack frame in the Cortex-M3 version of
ThreadX. The top of the suspended thread's stack is pointed to by
tx_thread_stack_ptr in the associated thread control block TX_THREAD.
Stack Offset Stack Contents
0x00 r4
0x04 r5
0x08 r6
0x0C r7
0x10 r8
0x14 r9
0x18 r10
0x1C r11
0x20 r0 (Hardware stack starts here!!)
0x24 r1
0x28 r2
0x2C r3
0x30 r12
0x34 lr
0x38 pc
0x3C xPSR
7. Improving Performance
The distribution version of ThreadX is built without any compiler
optimizations. This makes it easy to debug because you can trace or set
breakpoints inside of ThreadX itself. Of course, this costs some
performance. To make ThreadX run faster, you can change the tx.gpj project
to disable debug information and enable the desired optimizations.
In addition, you can eliminate the ThreadX basic API error checking by
compiling your application code with the symbol TX_DISABLE_ERROR_CHECKING
defined before tx_api.h is included.
8. Interrupt Handling
ThreadX provides complete and high-performance interrupt handling for Cortex-M3
targets. There are a certain set of requirements that are defined in the
following sub-sections:
8.1 Vector Area
The Cortex-M3 vectors start at the label __tx_vectors. The application may modify
the vector area according to its needs.
8.2 Managed Interrupts
A ThreadX managed interrupt is defined below. By following these conventions, the
application ISR is then allowed access to various ThreadX services from the ISR.
Here is the standard template for managed ISRs in ThreadX:
.globl __tx_IntHandler
__tx_IntHandler:
PUSH {lr}
BL _tx_thread_context_save
/* Do interrupt handler work here */
B _tx_thread_context_restore
9. Revision History
For generic code revision information, please refer to the readme_threadx_generic.txt
file, which is included in your distribution. The following details the revision
information associated with this specific port of ThreadX:
04-02-2021 Release 6.1.6 changes:
tx_port.h Updated macro definition
03-02-2021 The following files were changed/added for version 6.1.5:
tx_thread_schedule.s Added low power feature
05/19/2020 Initial ThreadX version of Cortex-M3/Green Hills port.
Copyright(c) 1996-2020 Microsoft Corporation
https://azure.com/rtos
|
