blob: 93964242582ad8015f4a0780e49dea92f0e7ac27 (
plain)
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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
# Understanding QMK's Code
This document attempts to explain how the QMK firmware works from a very high level. It assumes you understand basic programming concepts but does not (except where needed to demonstrate) assume familiarity with C. It assumes that you have a basic understanding of the following documents:
* [Introduction](getting_started_introduction.md)
* [How Keyboards Work](how_keyboards_work.md)
* [FAQ](faq.md)
## Startup
You can think of QMK as no different from any other computer program. It is started, performs its tasks, and then ends. The entry point for the program is the `main()` function, just like it is on any other C program. However, for a newcomer to QMK it can be confusing because the `main()` function appears in multiple places, and it can be hard to tell which one to look at.
The reason for this is the different platforms that QMK supports. The most common platform is `lufa`, which runs on AVR processors such at the atmega32u4. We also support `chibios` and `vusb`.
We'll focus on AVR processors for the moment, which use the `lufa` platform. You can find the `main()` function in [tmk_core/protocol/lufa/lufa.c](https://github.com/qmk/qmk_firmware/blob/e1203a222bb12ab9733916164a000ef3ac48da93/tmk_core/protocol/lufa/lufa.c#L1028). If you browse through that function you'll find that it initializes any hardware that has been configured (including USB to the host) and then it starts the core part of the program with a [`while(1)`](https://github.com/qmk/qmk_firmware/blob/e1203a222bb12ab9733916164a000ef3ac48da93/tmk_core/protocol/lufa/lufa.c#L1069). This is [The Main Loop](#the-main-loop).
## The Main Loop
This section of code is called "The Main Loop" because it's responsible for looping over the same set of instructions forever. This is where QMK dispatches out to the functions responsible for making the keyboard do everything it is supposed to do. At first glance it can look like a lot of functionality but most of the time the code will be disabled by `#define`'s.
```
keyboard_task();
```
This is where all the keyboard specific functionality is dispatched. The source code for `keyboard_task()` can be found in [tmk_core/common/keyboard.c](https://github.com/qmk/qmk_firmware/blob/e1203a222bb12ab9733916164a000ef3ac48da93/tmk_core/common/keyboard.c#L216), and it is responsible for detecting changes in the matrix and turning status LEDs on and off.
|
