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
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011,2012,2013 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
ChibiOS/RT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file chvt.c
* @brief Real Time Counter and Measurement module code.
*
* @addtogroup realtime_counter
* @details Realtime Counter APIs and services.
*
* <h2>Operation mode</h2>
* The realtime counter is a fast HW counter that counts upward at
* regular intervals. This counted can be used for small and accurate
* delays, time stamp and time measurement.
*
* <h2>Notes</h2>
* On those architectures where such a counter is not implemented
* the system time counter is used instead. Of course the system
* time counter usually has a much lower resolution than a real
* HW counter.
* @{
*/
#include "ch.h"
#if CH_CFG_USE_RT || defined(__DOXYGEN__)
/*===========================================================================*/
/* Module local definitions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported variables. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local types. */
/*===========================================================================*/
/*===========================================================================*/
/* Module local variables. */
/*===========================================================================*/
/**
* @brief Subsystem calibration value.
*/
static rtcnt_t measurement_offset;
/*===========================================================================*/
/* Module local functions. */
/*===========================================================================*/
/*===========================================================================*/
/* Module exported functions. */
/*===========================================================================*/
/**
* @brief Initializes the realtime counter unit.
*
* @init
*/
void _rt_init(void) {
time_measurement_t tm;
/* Time Measurement subsystem calibration, it does a null measurement
and calculates the call overhead which is subtracted to real
measurements.*/
measurement_offset = 0;
chRTTimeMeasurementObjectInit(&tm);
chRTTimeMeasurementStartX(&tm);
chRTTimeMeasurementStopX(&tm);
measurement_offset = tm.last;
}
/**
* @brief Realtime window test.
* @details This function verifies if the current realtime counter value
* lies within the specified range or not. The test takes care
* of the realtime counter wrapping to zero on overflow.
* @note When start==end then the function returns always true because the
* whole time range is specified.
* @note This function can be called from any context.
*
* @par Example 1
* Example of a guarded loop using the realtime counter. The loop implements
* a timeout after one second.
* @code
* rtcnt_t start = chRTGetCounterValue();
* rtcnt_t timeout = start + S2RTC(RTCCLK, 1);
* while (my_condition) {
* if (!chRTIsCounterWithin(start, timeout)
* return TIMEOUT;
* // Do something.
* }
* // Continue.
* @endcode
*
* @par Example 2
* Example of a loop that lasts exactly 50 microseconds.
* @code
* rtcnt_t start = chRTGetCounterValue();
* rtcnt_t timeout = start + US2RTC(RTCCLK, 50);
* while (chRTIsCounterWithin(start, timeout)) {
* // Do something.
* }
* // Continue.
* @endcode
*
* @param[in] start the start of the time window (inclusive)
* @param[in] end the end of the time window (non inclusive)
* @retval true current time within the specified time window.
* @retval false current time not within the specified time window.
*
* @special
*/
bool chRTIsCounterWithin(rtcnt_t start, rtcnt_t end) {
rtcnt_t now = chSysGetRealtimeCounterX();
return end > start ? (now >= start) && (now < end) :
(now >= start) || (now < end);
}
/**
* @brief Polled delay.
* @note The real delay is always few cycles in excess of the specified
* value.
* @note This function can be called from any context.
*
* @param[in] cycles number of cycles
*
* @special
*/
void chRTPolledDelay(rtcnt_t cycles) {
rtcnt_t start = chSysGetRealtimeCounterX();
rtcnt_t end = start + cycles;
while (chRTIsCounterWithin(start, end))
;
}
/**
* @brief Initializes a @p TimeMeasurement object.
*
* @param[out] tmp pointer to a @p TimeMeasurement structure
*
* @init
*/
void chRTTimeMeasurementObjectInit(time_measurement_t *tmp) {
tmp->best = (rtcnt_t)-1;
tmp->worst = (rtcnt_t)0;
tmp->cumulative = (rtcnt_t)0;
tmp->last = (rtcnt_t)0;
}
/**
* @brief Starts a measurement.
* @pre The @p time_measurement_t structure must be initialized.
* @note This function can be invoked from any context.
*
* @param[in,out] tmp pointer to a @p TimeMeasurement structure
*
* @special
*/
NOINLINE void chRTTimeMeasurementStartX(time_measurement_t *tmp) {
tmp->last = chSysGetRealtimeCounterX();
}
/**
* @brief Stops a measurement.
* @pre The @p time_measurement_t structure must be initialized.
* @note This function can be invoked from any context.
*
* @param[in,out] tmp pointer to a @p time_measurement_t structure
*
* @special
*/
NOINLINE void chRTTimeMeasurementStopX(time_measurement_t *tmp) {
rtcnt_t now = chSysGetRealtimeCounterX();
tmp->last = now - tmp->last - measurement_offset;
tmp->cumulative += tmp->last;
if (tmp->last > tmp->worst)
tmp->worst = tmp->last;
else if (tmp->last < tmp->best)
tmp->best = tmp->last;
}
#endif /* CH_CFG_USE_RT */
/** @} */
|