core: More RTC work

Former-commit-id: be2955b08d65c547d206d637ae499dbad892a87a
Former-commit-id: 19f0e4e6f9c598c35fb8172d93a1519f921eb27f

platform/rustboyadvance-sdl2/src/cli.yml

@@ -24,6 +24,10 @@ args:
             - flash64k
             - eeprom
             - autodetect
+    - rtc:
+        long: rtc
+        help: Force cartridge to have RTC
+        required: false
     - skip_bios:
         long: skip-bios
         help: Skip running bios and start from the ROM instead

platform/rustboyadvance-sdl2/src/main.rs

@@ -245,12 +245,17 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let mut rom_name = Path::new(&rom_path).file_name().unwrap().to_str().unwrap();
 
-    let gamepak = GamepakBuilder::new()
+    let mut builder = GamepakBuilder::new()
         .save_type(BackupType::try_from(
             matches.value_of("save_type").unwrap(),
         )?)
-        .file(Path::new(&rom_path))
+        .file(Path::new(&rom_path));
-        .build()?;
+
+    if matches.occurrences_of("rtc") != 0 {
+        builder = builder.with_rtc();
+    }
+
+    let gamepak = builder.build()?;
 
     let mut gba = GameBoyAdvance::new(
         bios_bin.into_boxed_slice(),

rustboyadvance-core/Cargo.toml

@@ -5,13 +5,14 @@ authors = ["Michel Heily <michelheily@gmail.com>"]
 edition = "2018"
 
 [dependencies]
-serde = { version = "1.0.104", features = ["derive"] }
+serde = { version = "1.0.104", features = ["derive", "rc"] }
 bincode = "1.2.1"
 byteorder = "1"
 num = "0.2.1"
 num-traits = "0.2"
 enum-primitive-derive = "^0.1"
 bit = "^0.1"
+chrono = "0.4"
 colored = "1.9"
 ansi_term = "0.12.1"
 hexdump = "0.1.0"
@@ -36,6 +37,7 @@ gdbstub = { version = "0.1.2", optional = true, features = ["std"] }
 ringbuf = "0.2.1"
 goblin = { version = "0.2", optional = true }
 fuzzy-matcher = { version = "0.3.4", optional = true }
+bit_reverse = "0.1.8"
 
 [target.'cfg(target_arch="wasm32")'.dependencies]
 instant = { version = "0.1.2", features = ["wasm-bindgen"] }

rustboyadvance-core/src/cartridge/builder.rs

@@ -14,12 +14,21 @@ use super::Cartridge;
 
 use super::loader::{load_from_bytes, load_from_file, LoadRom};
 
+#[derive(Debug)]
+pub enum GpioDeviceType {
+    Rtc,
+    SolarSensor,
+    Gyro,
+    None,
+}
+
 #[derive(Debug)]
 pub struct GamepakBuilder {
     path: Option<PathBuf>,
     bytes: Option<Box<[u8]>>,
     save_path: Option<PathBuf>,
     save_type: BackupType,
+    gpio_device: GpioDeviceType,
     create_backup_file: bool,
 }
 
@@ -30,6 +39,7 @@ impl GamepakBuilder {
             path: None,
             save_path: None,
             bytes: None,
+            gpio_device: GpioDeviceType::None,
             create_backup_file: true,
         }
     }
@@ -84,6 +94,11 @@ impl GamepakBuilder {
         self
     }
 
+    pub fn with_rtc(mut self) -> Self {
+        self.gpio_device = GpioDeviceType::Rtc;
+        self
+    }
+
     pub fn build(mut self) -> GBAResult<Cartridge> {
         let (bytes, symbols) = if let Some(bytes) = self.bytes {
             match load_from_bytes(bytes.to_vec())? {
@@ -127,7 +142,14 @@ impl GamepakBuilder {
 
         let backup = create_backup(self.save_type, self.save_path);
 
-        let gpio = Gpio::new();
+        let gpio = match self.gpio_device {
+            GpioDeviceType::None => Gpio::new_none(),
+            GpioDeviceType::Rtc => {
+                info!("Emulating RTC!");
+                Gpio::new_rtc()
+            }
+            _ => unimplemented!("Gpio device {:?} not implemented", self.gpio_device),
+        };
 
         let size = bytes.len();
         Ok(Cartridge {

rustboyadvance-core/src/cartridge/gpio.rs

@@ -4,44 +4,73 @@ use super::{GPIO_PORT_CONTROL, GPIO_PORT_DATA, GPIO_PORT_DIRECTION};
 use bit::BitIndex;
 use serde::{Deserialize, Serialize};
 
-use std::cell::RefCell;
+/// Struct holding the logical state of a serial port
+#[repr(transparent)]
+#[derive(Serialize, Deserialize, Copy, Clone, Debug)]
+pub struct GpioPort(u16);
+
+impl GpioPort {
+    pub fn get(&self) -> u16 {
+        self.0
+    }
+
+    pub fn set(&mut self, value: u16) {
+        self.0 = value & 1;
+    }
+
+    pub fn high(&self) -> bool {
+        self.0 != 0
+    }
+
+    pub fn low(&self) -> bool {
+        self.0 == 0
+    }
+}
+
+pub const GPIO_LOW: GpioPort = GpioPort(0);
+pub const GPIO_HIGH: GpioPort = GpioPort(1);
 
 #[derive(Serialize, Deserialize, Copy, Clone, Debug, PartialEq)]
-enum GpioDirection {
+pub enum GpioDirection {
+    /// GPIO to GBA
     In = 0,
+    /// GBA to GPIO
     Out = 1,
 }
 
+pub type GpioState = [GpioDirection; 4];
+
 #[derive(Serialize, Deserialize, Copy, Clone, Debug, PartialEq)]
 enum GpioPortControl {
     WriteOnly = 0,
     ReadWrite = 1,
 }
 
-trait GpioDevice: Sized {
+pub trait GpioDevice: Sized {
-    fn write(&mut self);
+    fn write(&mut self, gpio_state: &GpioState, data: u16);
-    fn read(&mut self);
+    fn read(&self, gpio_state: &GpioState) -> u16;
-}
-
-enum GpioDeviceType {
-    Rtc,
-    SolarSensor,
-    Gyro,
-    None,
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct Gpio {
-    rtc: Option<RefCell<Rtc>>,
+    rtc: Option<Rtc>,
-    direction: [GpioDirection; 4],
+    direction: GpioState,
     control: GpioPortControl,
 }
 
 impl Gpio {
-    pub fn new() -> Self {
+    pub fn new_none() -> Self {
         Gpio {
             rtc: None,
-            direction: [GpioDirection::In; 4],
+            direction: [GpioDirection::Out; 4],
+            control: GpioPortControl::WriteOnly,
+        }
+    }
+
+    pub fn new_rtc() -> Self {
+        Gpio {
+            rtc: Some(Rtc::new()),
+            direction: [GpioDirection::Out; 4],
             control: GpioPortControl::WriteOnly,
         }
     }
@@ -52,7 +81,13 @@ impl Gpio {
 
     pub fn read(&self, addr: u32) -> u16 {
         match addr {
-            GPIO_PORT_DATA => unimplemented!(),
+            GPIO_PORT_DATA => {
+                if let Some(rtc) = &self.rtc {
+                    rtc.read(&self.direction)
+                } else {
+                    0
+                }
+            }
             GPIO_PORT_DIRECTION => {
                 let mut direction = 0u16;
                 for i in 0..4 {
@@ -65,17 +100,30 @@ impl Gpio {
         }
     }
 
-    pub fn write(&mut self, addr: u32) -> u16 {
+    pub fn write(&mut self, addr: u32, value: u16) {
         match addr {
-            GPIO_PORT_DATA => unimplemented!(),
+            GPIO_PORT_DATA => {
+                if let Some(rtc) = &mut self.rtc {
+                    rtc.write(&self.direction, value);
+                }
+            }
             GPIO_PORT_DIRECTION => {
-                let mut direction = 0u16;
                 for i in 0..4 {
-                    direction.set_bit(i, self.direction[i] == GpioDirection::Out);
+                    if value.bit(i) {
+                        self.direction[i] = GpioDirection::Out;
+                    } else {
+                        self.direction[i] = GpioDirection::In;
                     }
-                direction
                 }
-            GPIO_PORT_CONTROL => self.control as u16,
+            }
+            GPIO_PORT_CONTROL => {
+                info!("GPIO port control: {:?}", self.control);
+                self.control = if value != 0 {
+                    GpioPortControl::ReadWrite
+                } else {
+                    GpioPortControl::WriteOnly
+                };
+            }
             _ => unreachable!(),
         }
     }

rustboyadvance-core/src/cartridge/mod.rs

@@ -21,9 +21,9 @@ mod builder;
 mod loader;
 pub use builder::GamepakBuilder;
 
-pub const GPIO_PORT_DATA: u32 = 0x0800_00C4;
+pub const GPIO_PORT_DATA: u32 = 0xC4;
-pub const GPIO_PORT_DIRECTION: u32 = 0x0800_00C6;
+pub const GPIO_PORT_DIRECTION: u32 = 0xC6;
-pub const GPIO_PORT_CONTROL: u32 = 0x0800_00C8;
+pub const GPIO_PORT_CONTROL: u32 = 0xC8;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub enum BackupMedia {
@@ -56,7 +56,7 @@ use super::sysbus::consts::*;
 pub const EEPROM_BASE_ADDR: u32 = 0x0DFF_FF00;
 
 fn is_gpio_access(addr: u32) -> bool {
-    match addr {
+    match addr & 0x1ff_ffff {
         GPIO_PORT_DATA | GPIO_PORT_DIRECTION | GPIO_PORT_CONTROL => true,
         _ => false,
     }
@@ -82,8 +82,11 @@ impl Bus for Cartridge {
     }
 
     fn read_16(&self, addr: u32) -> u16 {
-        if is_gpio_access(addr) && self.gpio.is_readable() {
+        if is_gpio_access(addr) {
-            return self.gpio.read(addr);
+            if !(self.gpio.is_readable()) {
+                info!("trying to read GPIO when reads are not allowed");
+            }
+            return self.gpio.read(addr & 0x1ff_ffff);
         }
 
         if addr & 0xff000000 == GAMEPAK_WS2_HI
@@ -109,7 +112,7 @@ impl Bus for Cartridge {
 
     fn write_16(&mut self, addr: u32, value: u16) {
         if is_gpio_access(addr) {
-            self.gpio.write(addr);
+            self.gpio.write(addr & 0x1ff_ffff, value);
             return;
         }
 

rustboyadvance-core/src/cartridge/rtc.rs

@@ -1,6 +1,30 @@
+use bit::BitIndex;
+use bit_reverse::LookupReverse;
+use chrono::prelude::*;
 use serde::{Deserialize, Serialize};
 
-#[derive(Serialize, Deserialize, Clone, Debug)]
+use num::FromPrimitive;
+
+use std::cmp;
+
+use super::gpio::{GpioDevice, GpioDirection, GpioPort, GpioState, GPIO_LOW};
+
+fn num2bcd(mut num: u8) -> u8 {
+    num = cmp::min(num, 99);
+
+    let mut bcd = 0;
+    let mut digit = 1;
+
+    while num > 0 {
+        let x = num % 10;
+        bcd += x * digit;
+        digit = digit << 4;
+        num /= 10;
+    }
+    bcd
+}
+
+#[derive(Serialize, Deserialize, Clone, Copy, Debug)]
 enum Port {
     #[doc("Serial Clock")]
     Sck = 0,
@@ -10,18 +34,580 @@ enum Port {
     Cs = 2,
 }
 
+impl Port {
+    #[inline]
+    pub fn index(self) -> usize {
+        self as usize
+    }
+}
+
+/// RTC Registers codes in the GBA
+#[derive(Primitive, Serialize, Deserialize, Clone, Copy, Debug, PartialEq)]
+enum RegisterKind {
+    ForceReset = 0,
+    DateTime = 2,
+    ForceIrq = 3,
+    Status = 4,
+    Time = 6,
+    Free = 7,
+}
+
+impl RegisterKind {
+    fn param_count(&self) -> u8 {
+        use RegisterKind::*;
+        match self {
+            ForceReset => 0,
+            DateTime => 7,
+            ForceIrq => 0,
+            Status => 1,
+            Time => 3,
+            Free => 0,
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq)]
+enum State {
+    Idle,
+    WaitForChipSelect,
+    GetCommandByte,
+    RxFromMaster {
+        reg: RegisterKind,
+        byte_count: u8,
+        byte_index: u8,
+    },
+    TxToMaster {
+        byte_count: u8,
+        byte_index: u8,
+    },
+}
+
+/// A Simple LSB-first 8-bit queue
+#[derive(Serialize, Deserialize, Clone, DebugStub)]
+struct SerialBuffer {
+    byte: u8,
+    counter: usize,
+}
+
+impl SerialBuffer {
+    fn new() -> Self {
+        SerialBuffer {
+            byte: 0,
+            counter: 0,
+        }
+    }
+
+    #[inline]
+    fn push_bit(&mut self, bit: bool) {
+        if self.counter == 8 {
+            return;
+        }
+        self.byte.set_bit(self.counter, bit);
+        self.counter += 1;
+    }
+
+    #[inline]
+    fn pop_bit(&mut self) -> bool {
+        if self.counter > 0 {
+            let result = self.byte.bit(0);
+            self.byte = self.byte.wrapping_shr(1);
+            self.counter -= 1;
+            result
+        } else {
+            false
+        }
+    }
+
+    fn reset(&mut self) {
+        self.byte = 0;
+        self.counter = 0;
+    }
+
+    fn count(&self) -> usize {
+        self.counter
+    }
+
+    fn is_empty(&self) -> bool {
+        self.count() == 0
+    }
+
+    fn is_full(&self) -> bool {
+        self.count() == 8
+    }
+
+    fn value(&self) -> Option<u8> {
+        if self.is_empty() {
+            None
+        } else {
+            let mask = if self.is_full() {
+                0b11111111
+            } else {
+                (1 << self.counter) - 1
+            };
+            Some(self.byte & u8::from(mask))
+        }
+    }
+
+    fn load_byte(&mut self, value: u8) {
+        self.byte = value;
+        self.counter = 8;
+    }
+
+    fn take_byte(&mut self) -> Option<u8> {
+        let result = self.value();
+        self.reset();
+        result
+    }
+}
+
 /// Model of the S3511 8pin RTC
 #[derive(Serialize, Deserialize, Clone, Debug)]
-pub struct Rtc {}
+pub struct Rtc {
+    state: State,
+    sck: GpioPort,
+    sio: GpioPort,
+    cs: GpioPort,
+    status: registers::StatusRegister,
+    serial_buffer: SerialBuffer,
+    internal_buffer: [u8; 8],
+}
 
 impl Rtc {
     pub fn new() -> Self {
-        Rtc {}
+        Rtc {
+            state: State::Idle,
+            sck: GPIO_LOW,
+            sio: GPIO_LOW,
+            cs: GPIO_LOW,
+            status: registers::StatusRegister {
+                mode_24h: true,
+                ..Default::default()
+            },
+            serial_buffer: SerialBuffer::new(),
+            internal_buffer: [0; 8],
+        }
     }
 
-    pub fn read_port(port: usize) -> u8 {
+    fn serial_read(&mut self) {
-        0
+        self.serial_buffer.push_bit(self.sio.high());
     }
 
-    pub fn write_port(port: usize) {}
+    fn force_reset(&mut self) {
+        self.serial_buffer.reset();
+        self.state = State::Idle;
+        self.status.write(0);
+        // TODO according to the datasheet, the date time registers should reset to 0-0-0-0..
+    }
+
+    /// Loads a register contents into an internal buffer
+    fn load_register(&mut self, r: RegisterKind) {
+        match r {
+            RegisterKind::Status => self.internal_buffer[0] = self.status.read(),
+            RegisterKind::DateTime => {
+                let local: DateTime<Local> = Local::now();
+                let year = local.year();
+                assert!(year >= 2000 && year <= 2099); // Wonder if I will leave to see this assert fail
+
+                let hour = if self.status.mode_24h {
+                    local.hour()
+                } else {
+                    let (_, hour12) = local.hour12();
+                    hour12 - 1
+                };
+
+                self.internal_buffer[0] = num2bcd((year % 100) as u8);
+                self.internal_buffer[1] = num2bcd(local.month() as u8);
+                self.internal_buffer[2] = num2bcd(local.day() as u8);
+                self.internal_buffer[3] = num2bcd(local.weekday().number_from_monday() as u8);
+                self.internal_buffer[4] = num2bcd(hour as u8);
+                self.internal_buffer[5] = num2bcd(local.minute() as u8);
+                self.internal_buffer[6] = num2bcd(local.second() as u8);
+
+                println!(
+                    "DateTime result: {:x?} dt={:?}",
+                    self.internal_buffer, local
+                );
+            }
+            RegisterKind::Time => {
+                let local: DateTime<Local> = Local::now();
+                let hour = if self.status.mode_24h {
+                    local.hour()
+                } else {
+                    let (_, hour12) = local.hour12();
+                    hour12 - 1
+                };
+                self.internal_buffer[0] = num2bcd(hour as u8);
+                self.internal_buffer[1] = num2bcd(local.minute() as u8);
+                self.internal_buffer[2] = num2bcd(local.second() as u8);
+            }
+            _ => warn!("RTC: read {:?} not implemented", r),
+        }
+    }
+
+    fn store_register(&mut self, r: RegisterKind) {
+        use RegisterKind::*;
+        info!("write register {:?} {:?}", r, self.internal_buffer);
+        match r {
+            Status => self.status.write(self.internal_buffer[0]),
+            ForceReset => self.force_reset(),
+            _ => warn!("RTC: write {:?} not implemented", r),
+        }
+    }
+}
+
+impl GpioDevice for Rtc {
+    fn write(&mut self, gpio_state: &GpioState, data: u16) {
+        assert_eq!(gpio_state[Port::Sck.index()], GpioDirection::Out);
+        assert_eq!(gpio_state[Port::Cs.index()], GpioDirection::Out);
+
+        let old_sck = self.sck;
+        let old_cs = self.cs;
+
+        self.sck.set(data.bit(Port::Sck.index()) as u16);
+        self.cs.set(data.bit(Port::Cs.index()) as u16);
+
+        let sck_rising_edge = old_sck.low() && self.sck.high();
+        let sck_falling_edge = old_sck.high() && self.sck.low();
+
+        if sck_falling_edge && gpio_state[Port::Sio.index()] == GpioDirection::Out {
+            self.sio.set(data.bit(Port::Sio.index()) as u16);
+        }
+
+        if self.cs.high() && old_cs.low() {
+            trace!("RTC CS went from low to high!");
+        }
+
+        use State::*;
+        match self.state {
+            Idle => {
+                if self.sck.high() && self.cs.low() {
+                    self.state = WaitForChipSelect;
+                }
+            }
+            WaitForChipSelect => {
+                if self.sck.high() && self.cs.high() {
+                    self.state = GetCommandByte;
+                    self.serial_buffer.reset();
+                }
+            }
+            GetCommandByte => {
+                if !sck_falling_edge {
+                    return;
+                }
+
+                // receive bit
+                self.serial_read();
+                if !self.serial_buffer.is_full() {
+                    return;
+                }
+
+                // finished collecting all the bits
+                let mut command = self.serial_buffer.value().unwrap();
+                self.serial_buffer.reset();
+
+                let lsb_first = command.bit_range(0..4) == 0b0110;
+                if !lsb_first && command.bit_range(4..8) != 0b0110 {
+                    panic!("RTC bad command format");
+                }
+
+                if !lsb_first {
+                    command = command.swap_bits();
+                }
+
+                let reg = RegisterKind::from_u8(command.bit_range(4..7)).expect("RTC bad register");
+                let byte_count = reg.param_count();
+
+                let is_read_operation = command.bit(7);
+
+                info!(
+                    "got command: {} {:?}",
+                    if is_read_operation { "READ" } else { "WRITE" },
+                    reg
+                );
+
+                if byte_count != 0 {
+                    if is_read_operation {
+                        self.load_register(reg);
+                        self.state = TxToMaster {
+                            byte_count,
+                            byte_index: 0,
+                        };
+                    } else {
+                        self.state = RxFromMaster {
+                            reg,
+                            byte_count,
+                            byte_index: 0,
+                        };
+                    }
+                } else {
+                    assert!(!is_read_operation);
+                    self.store_register(reg);
+                    self.state = Idle;
+                }
+
+                self.serial_buffer.reset();
+            }
+            TxToMaster {
+                byte_count,
+                byte_index,
+            } => {
+                if !sck_falling_edge {
+                    return;
+                }
+
+                let new_byte_index = if self.serial_buffer.is_empty() {
+                    byte_index + 1
+                } else {
+                    byte_index
+                };
+
+                if byte_count == new_byte_index {
+                    self.state = Idle;
+                    return;
+                }
+
+                if byte_index != new_byte_index {
+                    self.serial_buffer
+                        .load_byte(self.internal_buffer[byte_index as usize]);
+                }
+
+                assert_eq!(gpio_state[Port::Sio.index()], GpioDirection::In);
+                self.sio.set(self.serial_buffer.pop_bit() as u16);
+
+                self.state = TxToMaster {
+                    byte_count,
+                    byte_index: new_byte_index,
+                };
+            }
+            RxFromMaster {
+                reg,
+                byte_count,
+                byte_index,
+            } => {
+                if !sck_falling_edge {
+                    return;
+                }
+
+                assert_eq!(gpio_state[Port::Sio.index()], GpioDirection::Out);
+
+                self.serial_read();
+                if !self.serial_buffer.is_full() {
+                    return;
+                }
+
+                self.internal_buffer[byte_index as usize] = self.serial_buffer.take_byte().unwrap();
+
+                let byte_index = byte_index + 1;
+
+                if byte_index == byte_count {
+                    self.store_register(reg);
+                    self.state = Idle;
+                } else {
+                    self.state = RxFromMaster {
+                        reg,
+                        byte_count,
+                        byte_index,
+                    }
+                }
+            }
+        }
+    }
+
+    fn read(&self, _gpio_state: &GpioState) -> u16 {
+        let mut result = 0;
+        result.set_bit(Port::Sck.index(), self.sck.high());
+        result.set_bit(Port::Sio.index(), self.sio.high());
+        result.set_bit(Port::Cs.index(), self.cs.high());
+        result
+    }
+}
+
+mod registers {
+    use super::*;
+
+    #[derive(Serialize, Deserialize, Copy, Clone, Debug, Default)]
+    pub(super) struct StatusRegister {
+        pub(super) per_minute_irq: bool,
+        pub(super) mode_24h: bool,
+        pub(super) power_off: bool,
+    }
+
+    impl StatusRegister {
+        pub(super) fn read(&self) -> u8 {
+            let mut result = 0;
+            result.set_bit(3, self.per_minute_irq);
+            result.set_bit(6, self.mode_24h);
+            result.set_bit(7, self.power_off);
+            result
+        }
+
+        pub(super) fn write(&mut self, value: u8) {
+            self.per_minute_irq = value.bit(3);
+            self.mode_24h = value.bit(6);
+            self.power_off = value.bit(7);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::cell::Cell;
+    use std::rc::Rc;
+
+    fn transmit(rtc: &mut Rtc, gpio_state: &GpioState, bit: u8) {
+        rtc.write(&gpio_state, 0b0100_u16 | (u16::from(bit) << 1));
+        rtc.write(&gpio_state, 0b0101_u16);
+    }
+
+    fn receive_bytes(rtc: &mut Rtc, gpio_state: &GpioState, bytes: &mut [u8]) {
+        for byte in bytes.iter_mut() {
+            for i in 0..8 {
+                rtc.write(&gpio_state, 0b0100_u16);
+                let data = rtc.read(&gpio_state);
+                rtc.write(&gpio_state, 0b0101_u16);
+                byte.set_bit(i, data.bit(Port::Sio.index()));
+            }
+        }
+    }
+
+    fn transmit_bits(rtc: &mut Rtc, gpio_state: &GpioState, bits: &[u8]) {
+        for bit in bits.iter() {
+            transmit(rtc, gpio_state, *bit);
+        }
+    }
+
+    fn start_serial_transfer(rtc: &mut Rtc, gpio_state: &GpioState) {
+        assert_eq!(rtc.state, State::Idle);
+
+        // set CS low,
+        rtc.write(&gpio_state, 0b0001);
+        assert_eq!(rtc.state, State::WaitForChipSelect);
+
+        // set CS high, SCK rising edge
+        rtc.write(&gpio_state, 0b0101);
+        assert_eq!(rtc.state, State::GetCommandByte);
+    }
+
+    #[test]
+    fn test_serial_buffer() {
+        let mut serial_buffer = SerialBuffer::new();
+        assert_eq!(serial_buffer.value(), None);
+        serial_buffer.push_bit(true);
+        assert_eq!(serial_buffer.value(), Some(1));
+        let _ = serial_buffer.pop_bit();
+        assert_eq!(serial_buffer.value(), None);
+
+        serial_buffer.push_bit(false);
+        serial_buffer.push_bit(true);
+        serial_buffer.push_bit(true);
+        serial_buffer.push_bit(false);
+        assert_eq!(serial_buffer.count(), 4);
+
+        assert_eq!(serial_buffer.value(), Some(6));
+        let _ = serial_buffer.pop_bit();
+        assert_eq!(serial_buffer.value(), Some(3)); // pops are LSB first
+        let _ = serial_buffer.pop_bit();
+        assert_eq!(serial_buffer.count(), 2);
+        assert_eq!(serial_buffer.value(), Some(1));
+    }
+
+    macro_rules! setup_rtc {
+        ($rtc:ident, $gpio_state:ident) => {
+            let mut $rtc = Rtc::new(Rc::new(Cell::new(false)));
+            #[allow(unused_mut)]
+            let mut $gpio_state = [
+                GpioDirection::Out, /* SCK */
+                GpioDirection::Out, /* SIO */
+                GpioDirection::Out, /* CS */
+                GpioDirection::In,  /* dont-care */
+            ];
+        };
+    }
+
+    #[test]
+    fn test_rtc_status() {
+        setup_rtc!(rtc, gpio_state);
+
+        rtc.status.mode_24h = false;
+        start_serial_transfer(&mut rtc, &mut gpio_state);
+
+        // write Status register command
+        transmit_bits(&mut rtc, &gpio_state, &[0, 1, 1, 0, 0, 0, 1, 0]);
+        assert_eq!(
+            rtc.state,
+            State::RxFromMaster {
+                reg: RegisterKind::Status,
+                byte_count: 1,
+                byte_index: 0,
+            }
+        );
+
+        assert_eq!(rtc.status.mode_24h, false);
+
+        let mut serial_buffer = SerialBuffer::new();
+        serial_buffer.load_byte(
+            registers::StatusRegister {
+                mode_24h: true,
+                ..Default::default()
+            }
+            .read(),
+        );
+
+        while !serial_buffer.is_empty() {
+            transmit(&mut rtc, &gpio_state, serial_buffer.pop_bit() as u8);
+        }
+
+        assert!(rtc.serial_buffer.is_empty());
+        assert_eq!(rtc.status.mode_24h, true);
+
+        start_serial_transfer(&mut rtc, &mut gpio_state);
+
+        // read Status register command
+        transmit_bits(&mut rtc, &gpio_state, &[0, 1, 1, 0, 0, 0, 1, 1]);
+        assert_eq!(
+            rtc.state,
+            State::TxToMaster {
+                byte_count: 1,
+                byte_index: 0,
+            }
+        );
+
+        // adjust SIO pin
+        gpio_state[Port::Sio.index()] = GpioDirection::In;
+
+        let mut bytes = [0];
+        receive_bytes(&mut rtc, &gpio_state, &mut bytes);
+
+        let mut status = registers::StatusRegister::default();
+        status.write(bytes[0]);
+
+        assert_eq!(status.mode_24h, true);
+    }
+
+    #[test]
+    fn test_date_time() {
+        setup_rtc!(rtc, gpio_state);
+
+        start_serial_transfer(&mut rtc, &mut gpio_state);
+        transmit_bits(&mut rtc, &gpio_state, &[0, 1, 1, 0, 0, 1, 0, 1]);
+        assert_eq!(
+            rtc.state,
+            State::TxToMaster {
+                byte_count: 7,
+                byte_index: 0
+            }
+        );
+
+        gpio_state[Port::Sio.index()] = GpioDirection::In;
+        let mut bytes = [0; 7];
+        receive_bytes(&mut rtc, &gpio_state, &mut bytes);
+        assert_eq!(rtc.state, State::Idle);
+
+        println!("{:x?}", bytes);
+        let local: DateTime<Local> = Local::now();
+        assert_eq!(bytes[0], num2bcd((local.year() % 100) as u8));
+        assert_eq!(bytes[1], num2bcd(local.month() as u8));
+        assert_eq!(bytes[2], num2bcd(local.day() as u8));
+    }
 }

rustboyadvance-core/src/gba.rs

@@ -64,6 +64,7 @@ impl GameBoyAdvance {
         let sound_controller = Box::new(SoundController::new(
             audio_device.borrow().get_sample_rate() as f32,
         ));
+
         let io = IoDevices::new(gpu, sound_controller);
         let sysbus = Box::new(SysBus::new(io, bios_rom, gamepak));
 

rustboyadvance-core/src/sysbus.rs

@@ -282,7 +282,7 @@ macro_rules! memory_map {
                 $sb.io.$write_fn(addr, $value)
             }
             PALRAM_ADDR | VRAM_ADDR | OAM_ADDR => $sb.io.gpu.$write_fn($addr, $value),
-            GAMEPAK_WS0_LO | GAMEPAK_WS0_HI => {}
+            GAMEPAK_WS0_LO => $sb.cartridge.$write_fn($addr, $value),
             GAMEPAK_WS2_HI => $sb.cartridge.$write_fn($addr, $value),
             SRAM_LO | SRAM_HI => $sb.cartridge.$write_fn($addr, $value),
             _ => {