@@ -1,6 +1,7 @@
 #include "gba.h"
 
 #include "gba-gpio.h"
+#include "gba-sensors.h"
 
 #include <time.h>
 
@@ -12,6 +13,8 @@ static unsigned _rtcOutput(struct GBACartridgeGPIO* gpio);
 static void _rtcProcessByte(struct GBACartridgeGPIO* gpio);
 static void _rtcUpdateClock(struct GBACartridgeGPIO* gpio);
 static unsigned _rtcBCD(unsigned value);
+
+static void _gyroReadPins(struct GBACartridgeGPIO* gpio);
 
 static const int RTC_BYTES[8] = {
 	0, // Force reset
@@ -45,7 +48,7 @@ case GPIO_REG_CONTROL:
 		gpio->readWrite = value;
 		break;
 	default:
-		GBALog(0, GBA_LOG_WARN, "Invalid GPIO address");
+		GBALog(gpio->p, GBA_LOG_WARN, "Invalid GPIO address");
 	}
 
 	if (gpio->readWrite) {
@@ -73,6 +76,10 @@ void _readPins(struct GBACartridgeGPIO* gpio) {
 	if (gpio->gpioDevices & GPIO_RTC) {
 		_rtcReadPins(gpio);
 	}
+
+	if (gpio->gpioDevices & GPIO_GYRO) {
+		_gyroReadPins(gpio);
+	}
 }
 
 void _outputPins(struct GBACartridgeGPIO* gpio, unsigned pins) {
@@ -81,7 +88,9 @@ uint16_t old = gpio->gpioBase[0];
 		old &= gpio->direction;
 		gpio->gpioBase[0] = old | (pins & ~gpio->direction & 0xF);
 	}
-};
+}
+
+// == RTC
 
 void _rtcReadPins(struct GBACartridgeGPIO* gpio) {
 	// Transfer sequence:
@@ -115,7 +124,7 @@ if (gpio->p2) {
 				// GPIO direction should always != reading
 				if (gpio->dir1) {
 					if (gpio->rtc.command.reading) {
-						GBALog(0, GBA_LOG_GAME_ERROR, "Attempting to write to RTC while in read mode");
+						GBALog(gpio->p, GBA_LOG_GAME_ERROR, "Attempting to write to RTC while in read mode");
 					}
 					++gpio->rtc.bitsRead;
 					if (gpio->rtc.bitsRead == 8) {
@@ -168,7 +177,7 @@ case RTC_CONTROL:
 				break;
 			}
 		} else {
-			GBALog(0, GBA_LOG_WARN, "Invalid RTC command byte: %02X", gpio->rtc.bits);
+			GBALog(gpio->p, GBA_LOG_WARN, "Invalid RTC command byte: %02X", gpio->rtc.bits);
 		}
 	} else {
 		switch (gpio->rtc.command.command) {
@@ -176,7 +185,7 @@ case RTC_CONTROL:
 			gpio->rtc.control.packed = gpio->rtc.bits;
 			break;
 		case RTC_FORCE_IRQ:
-			GBALog(0, GBA_LOG_STUB, "Unimplemented RTC command %u", gpio->rtc.command.command);
+			GBALog(gpio->p, GBA_LOG_STUB, "Unimplemented RTC command %u", gpio->rtc.command.command);
 			break;
 		case RTC_RESET:
 		case RTC_DATETIME:
@@ -234,3 +243,38 @@ value /= 10;
 	counter += (value % 10) << 4;
 	return counter;
 }
+
+// == Gyro
+
+void GBAGPIOInitGyro(struct GBACartridgeGPIO* gpio) {
+	gpio->gpioDevices |= GPIO_GYRO;
+	gpio->gyroSample = 0;
+	gpio->gyroEdge = 0;
+}
+
+
+void _gyroReadPins(struct GBACartridgeGPIO* gpio) {
+	struct GBARotationSource* gyro = gpio->p->rotationSource;
+	if (!gyro) {
+		return;
+	}
+
+	if (gpio->p0) {
+		if (gyro->sample) {
+			gyro->sample(gyro);
+		}
+		int32_t sample = gyro->readGyroZ(gyro);
+
+		// Normalize to ~12 bits, focused on 0x6C0
+		gpio->gyroSample = (sample >> 21) + 0x6C0; // Crop off an extra bit so that we can't go negative
+	}
+
+	if (gpio->gyroEdge && !gpio->p1) {
+		// Write bit on falling edge
+		unsigned bit = gpio->gyroSample >> 15;
+		gpio->gyroSample <<= 1;
+		_outputPins(gpio, bit << 2);
+	}
+
+	gpio->gyroEdge = gpio->p1;
+}

@@ -64,6 +64,7 @@ uint8_t time[7];
 };
 
 struct GBACartridgeGPIO {
+	struct GBA* p;
 	int gpioDevices;
 	enum GPIODirection readWrite;
 	uint16_t* gpioBase;
@@ -89,11 +90,16 @@ uint16_t direction;
 	};
 
 	struct GBARTC rtc;
+
+	uint16_t gyroSample;
+	int gyroEdge;
 };
 
 void GBAGPIOInit(struct GBACartridgeGPIO* gpio, uint16_t* gpioBase);
 void GBAGPIOWrite(struct GBACartridgeGPIO* gpio, uint32_t address, uint16_t value);
 
 void GBAGPIOInitRTC(struct GBACartridgeGPIO* gpio);
+
+void GBAGPIOInitGyro(struct GBACartridgeGPIO* gpio);
 
 #endif

@@ -34,6 +34,7 @@ memory->fullBios = 0;
 	memory->wram = mmap(0, SIZE_WORKING_RAM, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
 	memory->iwram = mmap(0, SIZE_WORKING_IRAM, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
 	memory->rom = 0;
+	memory->gpio.p = memory->p;
 	memset(memory->io, 0, sizeof(memory->io));
 	memset(memory->dma, 0, sizeof(memory->dma));
 

@@ -0,0 +1,15 @@
+#ifndef GBA_SENSORS_H
+#define GBA_SENSORS_H
+
+#include <stdint.h>
+
+struct GBARotationSource {
+	void (*sample)(struct GBARotationSource*);
+
+	int32_t (*readTiltX)(struct GBARotationSource*);
+	int32_t (*readTiltY)(struct GBARotationSource*);
+
+	int32_t (*readGyroZ)(struct GBARotationSource*);
+};
+
+#endif

@@ -33,6 +33,7 @@ { 'EPXA', SAVEDATA_FLASH1M, GPIO_RTC },
 	{ 'EVXA', SAVEDATA_FLASH1M, GPIO_RTC },
 	{ 'E4XA', SAVEDATA_FLASH1M, GPIO_NONE },
 	{ 'EEPB', SAVEDATA_FLASH1M, GPIO_RTC },
+	{ 'EWZR', SAVEDATA_SRAM, GPIO_RUMBLE | GPIO_GYRO },
 	{ 0, 0, 0 }
 };
 
@@ -69,6 +70,7 @@ memset(gba->timers, 0, sizeof(gba->timers));
 
 	gba->springIRQ = 0;
 	gba->keySource = 0;
+	gba->rotationSource = 0;
 
 	gba->logLevel = GBA_LOG_INFO | GBA_LOG_WARN | GBA_LOG_ERROR;
 
@@ -484,6 +486,10 @@ }
 
 			if (_overrides[i].gpio & GPIO_RTC) {
 				GBAGPIOInitRTC(&gba->memory.gpio);
+			}
+
+			if (_overrides[i].gpio & GPIO_GYRO) {
+				GBAGPIOInitGyro(&gba->memory.gpio);
 			}
 			return;
 		}

@@ -54,6 +54,8 @@ GBA_KEY_R = 8,
 	GBA_KEY_L = 9
 };
 
+struct GBARotationSource;
+
 struct GBABoard {
 	struct ARMBoard d;
 	struct GBA* p;
@@ -85,6 +87,7 @@ } timers[4];
 
 	int springIRQ;
 	int* keySource;
+	struct GBARotationSource* rotationSource;
 
 	const char* activeFile;
 	const char* savefile;