diff --git a/adc.hpp b/adc.hpp
index a2f0d57..5d76a28 100644
--- a/adc.hpp
+++ b/adc.hpp
@@ -12,7 +12,7 @@ namespace adc {
 
 namespace detail {
 
-extern void (*fnAdcIntHandler)(uint16_t);
+extern void (*fnAdcIntHandler)(const uint16_t &);
 
 using reg_ptr_t = volatile uint8_t *;
 
@@ -46,6 +46,10 @@ class AdcImpl {
 
 		constexpr auto ctrlStatB = calcCtrlStatB();
 		*getRegPtr<Registers::CTRL_STAT_B_ADDR>() = ctrlStatB;
+
+		if constexpr (Cfg::MODE == Mode::FREE_RUNNING) {
+			*getRegPtr<Registers::CTRL_STAT_A_ADDR>() |= 1 << ControlFlagsA::START_CONV;
+		}
 	}
 
 	static constexpr auto calcRef()
@@ -85,9 +89,10 @@ class AdcImpl {
 	{
 		uint8_t ctrlStatA = 1 << ControlFlagsA::ENABLE;
 
-		if constexpr (Cfg::MODE == Mode::AUTO) {
+		if constexpr (Cfg::MODE == Mode::AUTO || Cfg::MODE == Mode::FREE_RUNNING) {
 			ctrlStatA |= 1 << ControlFlagsA::AUTO_TRIGGER;
-		} else if (interruptEnable) {
+		}
+		if (interruptEnable) {
 			ctrlStatA |= 1 << ControlFlagsA::CONV_COMPLETE_INT_ENABLE;
 		}
 
@@ -125,7 +130,7 @@ class Adc {
 
 template <typename Cfg, io::P pin>
 class Adc<Cfg, io::P, pin> : public detail::AdcImpl<Cfg> {
-	using callback_t = void (*)(uint16_t);
+	using callback_t = void (*)(const uint16_t &);
 
   public:
 	static_assert(detail::supports_adc_v<pin>, "Pin does not support ADC");
@@ -197,7 +202,7 @@ namespace detail {
 
 #if defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega328P__)
 
-void (*fnAdcIntHandler)(uint16_t) = nullptr;
+void (*fnAdcIntHandler)(const uint16_t &) = nullptr;
 
 ISR(ADC_vect)
 {