STM32 LPTICKER : read counter

jeromecoutant · jeromecoutant · commit 08b06a49a207 · 2018-04-23T17:34:08.000+02:00
diff --git a/targets/TARGET_STM/lp_ticker.c b/targets/TARGET_STM/lp_ticker.c
@@ -179,7 +179,12 @@ static void LPTIM1_IRQHandler(void)
 uint32_t lp_ticker_read(void)
 {
     uint32_t lp_time = LPTIM1->CNT;
-    return lp_time;     
+    /* Reading the LPTIM_CNT register may return unreliable values.
+    It is necessary to perform two consecutive read accesses and verify that the two returned values are identical */
+    while (lp_time != LPTIM1->CNT) {
+        lp_time = LPTIM1->CNT;
+    }
+    return lp_time;
 }
 
 void lp_ticker_set_interrupt(timestamp_t timestamp)

Original file line number	Diff line number	Diff line change
`@@ -179,7 +179,12 @@ static void LPTIM1_IRQHandler(void)`
`179`	`179`	`uint32_t lp_ticker_read(void)`
`180`	`180`	`{`
`181`	`181`	`uint32_t lp_time = LPTIM1->CNT;`
`182`		`- return lp_time;`
	`182`	`+ /* Reading the LPTIM_CNT register may return unreliable values.`
	`183`	`+ It is necessary to perform two consecutive read accesses and verify that the two returned values are identical */`
	`184`	`+ while (lp_time != LPTIM1->CNT) {`
	`185`	`+ lp_time = LPTIM1->CNT;`
	`186`	`+ }`
	`187`	`+ return lp_time;`
`183`	`188`	`}`
`184`	`189`
`185`	`190`	`void lp_ticker_set_interrupt(timestamp_t timestamp)`