From cf636ec095f94f451436599eddc836c2783053e2 Mon Sep 17 00:00:00 2001
From: Alex Voinea <voinea.dragos.alexandru@gmail.com>
Date: Tue, 20 Jul 2021 18:23:42 +0300
Subject: [PATCH] Fix configuration compute() math

---
 src/hal/watchdog.h | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/hal/watchdog.h b/src/hal/watchdog.h
index 84a839e..9a3edde 100644
--- a/src/hal/watchdog.h
+++ b/src/hal/watchdog.h
@@ -14,7 +14,7 @@ constexpr uint8_t reloadBits = 0; //number of bits in the reload register
 #elif defined(__STM32__) //@todo to be changed to the final form
 constexpr uint32_t F_WDT = 32000; //frequency of the watchdog unit in Hz
 constexpr uint32_t basePrescaler = 4; //what prescalerBits==0 actually does.
-constexpr uint8_t maxPrescaler = 7; //the maximum value prescalerBits can take
+constexpr uint8_t maxPrescaler = 6; //the maximum value prescalerBits can take
 constexpr uint8_t reloadBits = 12; //number of bits in the reload register
 #endif
 
@@ -24,16 +24,15 @@ struct configuration {
 
 public:
     static constexpr configuration compute(float timeout) {
-        constexpr float tickPeriod = 1 / (float)F_WDT;
         uint8_t prescalerBits = 0;
-        uint16_t reload = 0;
-        while (tickPeriod * (basePrescaler << prescalerBits) < timeout) {
+        uint32_t ticks = timeout * F_WDT / (basePrescaler * (1 << prescalerBits));
+        while ((ticks >= (1 << reloadBits)) && (prescalerBits < maxPrescaler)) {
             prescalerBits++;
+            ticks = timeout * F_WDT / (basePrescaler * (1 << prescalerBits));
         }
-        if (timeout)
-            reload = static_cast<uint16_t>(((timeout * (1 << reloadBits)) / (tickPeriod * (basePrescaler << prescalerBits)))) - 1;
-
-        configuration config = { prescalerBits, reload };
+        if ((prescalerBits == 0) && (ticks == 0))
+            ticks = 1; //1 tick is minimum
+        configuration config = { prescalerBits, static_cast<uint16_t>(ticks - 1) };
         return config;
     }
 };