Attempt some inspection.

Components/I2C/I2C.cpp

@@ -25,9 +25,44 @@ bool Bus::clock() {
 }
 
 void Bus::set_clock_data(bool clock_pulled, bool data_pulled) {
-	// TODO: all intelligence.
+	const bool has_new_bit = clock_pulled && !clock_;
 	clock_ = clock_pulled;
 	data_ = data_pulled;
+
+	// TODO: "Stop condition: SDA goes high after SCL (?)".
+
+	if(has_new_bit) {
+		// Test for a start bit.
+		//
+		// "Start condition: SDA goes low before SCL".
+		if(input_count_ < 0 && data_) {
+			input_count_ = 0;
+		}
+
+		// Accumulate if started.
+		if(input_count_ >= 0) {
+			input_ = uint16_t((input_ << 1) | (data_pulled ? 0 : 1));
+			++input_count_;
+		}
+
+		// Test for meaning.
+		switch(phase_) {
+			case Phase::AwaitingAddress:
+				if(input_count_ == 9) {
+					printf("Calling %02x?", uint8_t(input_));
+
+					auto pair = peripherals_.find(uint8_t(input_));
+					if(pair != peripherals_.end()) {
+						active_peripheral_ = pair->second;
+						// TODO: device found; pull data low for the next clock.
+					}
+				}
+			break;
+
+			case Phase::CollectingData:
+			break;
+		}
+	}
 }
 
 void Bus::add_peripheral(Peripheral *peripheral, int address) {

Components/I2C/I2C.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <cstdint>
 #include <unordered_map>
 
 namespace I2C {
@@ -34,6 +35,16 @@ private:
 	bool data_ = false;
 	bool clock_ = false;
 	std::unordered_map<int, Peripheral *> peripherals_;
+
+	uint16_t input_ = 0xffff;
+	int input_count_ = -1;
+
+	Peripheral *active_peripheral_ = nullptr;
+
+	enum class Phase {
+		AwaitingAddress,
+		CollectingData,
+	} phase_ = Phase::AwaitingAddress;
 };
 
 }