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[API] Added option to modify RTC source #926

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Merged
merged 2 commits into from
Mar 9, 2015
Merged

[API] Added option to modify RTC source #926

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f0d04f5
[API] Added option to modify RTC source
Sissors Feb 22, 2015
4a184d9
Made attach_rtc with disabled irqs
Sissors Feb 28, 2015
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11 changes: 11 additions & 0 deletions libraries/mbed/api/rtc_time.h
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,17 @@ extern "C" {
*/
void set_time(time_t t);

/** Attach an external RTC to be used for the C time functions
*
* Do not call this function from an interrupt while an RTC read/write operation may be occurring
*
* @param read_rtc pointer to function which returns current UNIX timestamp
* @param write_rtc pointer to function which sets current UNIX timestamp, can be NULL
* @param init_rtc pointer to funtion which initializes RTC, can be NULL
* @param isenabled_rtc pointer to function wich returns if the rtc is enabled, can be NULL
*/
void attach_rtc(time_t (*read_rtc)(void), void (*write_rtc)(time_t), void (*init_rtc)(void), int (*isenabled_rtc)(void));

#ifdef __cplusplus
}
#endif
48 changes: 37 additions & 11 deletions libraries/mbed/common/rtc_time.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,18 @@
#include "rtc_time.h"
#include "us_ticker_api.h"

#if DEVICE_RTC
static void (*_rtc_init)(void) = rtc_init;
static int (*_rtc_isenabled)(void) = rtc_isenabled;
static time_t (*_rtc_read)(void) = rtc_read;
static void (*_rtc_write)(time_t t) = rtc_write;
#else
static void (*_rtc_init)(void) = NULL;
static int (*_rtc_isenabled)(void) = NULL;
static time_t (*_rtc_read)(void) = NULL;
static void (*_rtc_write)(time_t t) = NULL;
#endif

#ifdef __cplusplus
extern "C" {
#endif
Expand All @@ -29,15 +41,16 @@ time_t time(time_t *timer)
#endif

{
#if DEVICE_RTC
if (!(rtc_isenabled())) {
set_time(0);
if (_rtc_isenabled != NULL) {
if (!(_rtc_isenabled())) {
set_time(0);
}
}
time_t t = rtc_read();

#else

time_t t = 0;
#endif
if (_rtc_read != NULL) {
t = _rtc_read();
}

if (timer != NULL) {
*timer = t;
Expand All @@ -46,10 +59,12 @@ time_t time(time_t *timer)
}

void set_time(time_t t) {
#if DEVICE_RTC
rtc_init();
rtc_write(t);
#endif
if (_rtc_init != NULL) {
_rtc_init();
}
if (_rtc_write != NULL) {
_rtc_write(t);
}
}

clock_t clock() {
Expand All @@ -58,6 +73,17 @@ clock_t clock() {
return t;
}

void attach_rtc(time_t (*read_rtc)(void), void (*write_rtc)(time_t), void (*init_rtc)(void), int (*isenabled_rtc)(void)) {
__disable_irq();
_rtc_read = read_rtc;
_rtc_write = write_rtc;
_rtc_init = init_rtc;
_rtc_isenabled = isenabled_rtc;
__enable_irq();
}
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This should not be an atomic operation?
So if I call this function, yes, I "switch RTC callbacks" to new ones but where is the code to for example:

  • force new RTC re-initialization.
    My point is I only call new rtc_init() when I set new time. Maybe I should have some flag saying I changed RTC API callbacks, just in case if someone calls rtc read/write I will reinit for him.

I probably missed something but I think some piece of comment / documentation about (example usage of: attach_rtc()) how it should work in source code would be great.

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Init is called as it is even now. set_time reinits RTC, and time() invokes set_time() if RTC is not enabled.

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Outside of init on which Martin already commented: Yes ideally it is atomic, and also the other RTC functions you don't want interrupted by attach. I might even do something nice with shadow variables. However: Is it really needed? There are a ton of mbed functions which can break when interrupting them (including for example changing pins of the same port to input/output). It seems to me to be in any normal use case a highly unlikely situation where this would interrupt anything: Normally you will call it at the start of your code.

For example usage, I published my test program (ignore lines 26/27, was debugging, not my own library I started with and helloworld was broken). This is using it with a C++ class, where for the functions I needed static member functions. If you do it purely C it would be easier, but this works fine. Should at least clarify how the attach_rtc is used: http://developer.mbed.org/users/Sissors/code/Adafruit_RTCLib/rev/09c202144d63. I don't think the init function will be used often in practise, easier to do that in the constructor.




#ifdef __cplusplus
}
#endif