This fixes problems when values such as 512..639 or 1024..1151 or ... or
32768..32895 are passed to iwdg_set_period_ms.
Signed-off-by: Filip Moc <d...@moc6.cz>
---
lib/stm32/common/iwdg_common_all.c | 54 +++++++++++++++++++-------------------
1 file changed, 27 insertions(+), 27 deletions(-)
diff --git a/lib/stm32/common/iwdg_common_all.c
b/lib/stm32/common/iwdg_common_all.c
index f2b1c1d8..1e299893 100644
--- a/lib/stm32/common/iwdg_common_all.c
+++ b/lib/stm32/common/iwdg_common_all.c
@@ -42,6 +42,7 @@ relevant bit is not set, the IWDG timer must be enabled by
software.
#define LSI_FREQUENCY 32000
#define COUNT_LENGTH 12
#define COUNT_MASK ((1 << COUNT_LENGTH)-1)
+#define PRESCALER_MAX 6
/*---------------------------------------------------------------------------*/
/** @brief IWDG Enable Watchdog Timer
@@ -73,42 +74,41 @@ reset until a system reset is issued.
void iwdg_set_period_ms(uint32_t period)
{
- uint32_t count, prescale, reload, exponent;
-
- /* Set the count to represent ticks of the 32kHz LSI clock */
- count = (period << 5);
-
- /* Strip off the first 12 bits to get the prescale value required */
- prescale = (count >> 12);
- if (prescale > 256) {
- exponent = IWDG_PR_DIV256; reload = COUNT_MASK;
- } else if (prescale > 128) {
- exponent = IWDG_PR_DIV256; reload = (count >> 8);
- } else if (prescale > 64) {
- exponent = IWDG_PR_DIV128; reload = (count >> 7);
- } else if (prescale > 32) {
- exponent = IWDG_PR_DIV64; reload = (count >> 6);
- } else if (prescale > 16) {
- exponent = IWDG_PR_DIV32; reload = (count >> 5);
- } else if (prescale > 8) {
- exponent = IWDG_PR_DIV16; reload = (count >> 4);
- } else if (prescale > 4) {
- exponent = IWDG_PR_DIV8; reload = (count >> 3);
- } else {
- exponent = IWDG_PR_DIV4; reload = (count >> 2);
- }
+ uint8_t prescale = 0;
+
+ /* Set the count to represent ticks of 8kHz clock (the 32kHz LSI clock
+ * divided by 4 = lowest prescaler setting)
+ */
+ uint32_t count = period << 3;
- /* Avoid the undefined situation of a zero count */
+ /* Prevent underflow */
if (count == 0) {
count = 1;
}
+ /* Shift count while increasing prescaler as many times as needed to
+ * fit into IWDG_RLR
+ */
+ while ((count-1) >> COUNT_LENGTH) {
+ count >>= 1;
+ prescale++;
+ }
+
+ /* IWDG_RLR actually holds count - 1 */
+ count--;
+
+ /* Clamp to max possible period */
+ if (prescale > PRESCALER_MAX) {
+ count = COUNT_MASK;
+ prescale = PRESCALER_MAX;
+ }
+
while (iwdg_prescaler_busy());
IWDG_KR = IWDG_KR_UNLOCK;
- IWDG_PR = exponent;
+ IWDG_PR = prescale;
while (iwdg_reload_busy());
IWDG_KR = IWDG_KR_UNLOCK;
- IWDG_RLR = (reload & COUNT_MASK);
+ IWDG_RLR = count & COUNT_MASK;
}
/*---------------------------------------------------------------------------*/
--
2.11.0
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