diff --git a/include/arm9/timer.h b/include/arm9/timer.h
index 710538d..c19b476 100644
--- a/include/arm9/timer.h
+++ b/include/arm9/timer.h
@@ -5,17 +5,17 @@
 
 
 
-#define TIMER_BASE_FREQ     (67027963.9305)
+#define TIMER_BASE_FREQ     (67027964.0)
 
 #define TIMER_COUNT_UP      (1u<<2) // For cascading at least 2 timers
 #define TIMER_IRQ_ENABLE    (1u<<6)
 #define TIMER_ENABLE        (1u<<7)
 
 // Convenience macros for calculating the ticks. Based on libnds
-#define TIMER_FREQ(n)       (0xFFFFu - (u16)(TIMER_BASE_FREQ / n))
-#define TIMER_FREQ_64(n)    (0xFFFFu - (u16)(TIMER_BASE_FREQ / 64.0 / n))
-#define TIMER_FREQ_256(n)   (0xFFFFu - (u16)(TIMER_BASE_FREQ / 256.0 / n))
-#define TIMER_FREQ_1024(n)  (0xFFFFu - (u16)(TIMER_BASE_FREQ / 1024.0 / n))
+#define TIMER_FREQ(n)       (0xFFFFu - (u16)(TIMER_BASE_FREQ / n) + 1)
+#define TIMER_FREQ_64(n)    (0xFFFFu - (u16)(TIMER_BASE_FREQ / 64.0 / n) + 1)
+#define TIMER_FREQ_256(n)   (0xFFFFu - (u16)(TIMER_BASE_FREQ / 256.0 / n) + 1)
+#define TIMER_FREQ_1024(n)  (0xFFFFu - (u16)(TIMER_BASE_FREQ / 1024.0 / n) + 1)
 
 
 typedef enum
@@ -35,9 +35,34 @@
 } TimerPrescaler;
 
 
-void TIMER_init(void);
-void TIMER_start(Timer timer, TimerPrescaler prescaler, u16 ticks, bool enableIrq);
-void TIMER_stop(Timer timer);
-void _timerSleep(u32 ticks); // Use the macro instead
 
-#define TIMER_sleep(ms)      _timerSleep(0xFFFFFFFFu - (u32)((TIMER_BASE_FREQ / 1024.0 / 1000.0) * ms))
+/**
+ * @brief      Resets/initializes the timer hardware. Should not be called manually.
+ */
+void TIMER_init(void);
+
+/**
+ * @brief      Starts a timer.
+ *
+ * @param[in]  timer      The timer to start.
+ * @param[in]  prescaler  The prescaler to use.
+ * @param[in]  ticks      The initial number of ticks. This is also the reload value on overflow.
+ * @param[in]  enableIrq  true if this timer should fire an interrupt on overflow.
+ */
+void TIMER_start(Timer timer, TimerPrescaler prescaler, u16 ticks, bool enableIrq);
+
+/**
+ * @brief      Stops a timer.
+ *
+ * @param[in]  timer  The timer to stop.
+ */
+void TIMER_stop(Timer timer);
+
+/**
+ * @brief      Halts the processor for the specified number of ticks. Use the macro below.
+ *
+ * @param[in]  ticks  The number of ticks.
+ */
+void _timerSleep(u32 ticks);
+
+#define TIMER_sleep(ms)      _timerSleep(0xFFFFFFFFu - (u32)((TIMER_BASE_FREQ / 1024.0 / 1000.0) * ms) + 1)
diff --git a/source/arm9/dev.c b/source/arm9/dev.c
index 7dc6d62..75dcd2b 100644
--- a/source/arm9/dev.c
+++ b/source/arm9/dev.c
@@ -136,7 +136,7 @@
 
 		if(!sdmmc_sd_is_active())
 		{
-			TIMER_sleep(250.5f); // Wait until the SD bus times out
+			TIMER_sleep(250.4f); // Wait until the SD bus times out
 			if(!sdmmc_sd_is_active()) return false; // Check again if a SD card is inserted
 		}