Adds sprite rendering (#22)

- Adds `ObjectAttributeEntry` for sprite entries in OAM.
- Adds `DirectMemoryAccessController` to handle DMA transfers from CPU memory to PPU OAM.
- Updates the PPU to render sprites.

Sources/SwiftNES/AddressableDevice.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 /// A protocol that describes a device that is addressable on a system bus.
 protocol AddressableDevice: AnyObject {
  /// The address range of the device.

Sources/SwiftNES/AudioReceiver.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 public protocol AudioReceiver: AnyObject {
  // TODO: Define an AudioReceiver.
  // TODO: Move protocol into an SDK package.

Sources/SwiftNES/Bus.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 /// Represents a bus that allows the CPU to read and write to various attached devices via memory address.
 final class Bus {
 
@@ -30,7 +28,7 @@ final class Bus {
  /// Initializes a bus with attached devices.
  ///
  /// - Parameters:
- /// - addressableDevices: The devices that can be addressed via this bus.
+ /// - addressableDevices: The ``AddressableDevice``s that can be addressed via the bus.
  init(addressableDevices: [any AddressableDevice]) throws {
  // TODO: Verify that there are no overlapping devices.
 
@@ -49,8 +47,8 @@ final class Bus {
  /// Read from or write to an address on the bus.
  ///
  /// - Parameters:
- /// - address: The address to read from or write to..
- /// - Returns: The value that was read from a device on the bus.
+ /// - address: The ``Address`` to read from or write to.
+ /// - Returns: The ``Value`` that was read from a device on the bus.
  subscript(address: Address) -> Value {
  get { read(from: address) }
  set { write(newValue, to: address) }
@@ -61,8 +59,8 @@ final class Bus {
  /// - Note: If a device does not respond to the address, `0` will be returned.
  ///
  /// - Parameters:
- /// - address: The address to read from.
- /// - Returns: The value that was read from a device on the bus.
+ /// - address: The ``Address`` to read from.
+ /// - Returns: The ``Value`` that was read from a device on the bus.
  func read(from address: Address) -> Value {
  guard let deviceToReadFromIndex = addressableReadDeviceRanges
  .firstIndex(where: { $0.contains(address) }) else { return 0 }
@@ -77,8 +75,8 @@ final class Bus {
  /// - Note: If a device does not respond to the address, this method does nothing.
  ///
  /// - Parameters:
- /// - value: The value to write to the bus.
- /// - address: The address to write to.
+ /// - value: The ``Value`` to write to the bus.
+ /// - address: The ``Address`` to write to.
  func write(_ value: Value, to address: Address) {
  guard let deviceToWriteToIndex = addressableWriteDeviceRanges
  .firstIndex(where: { $0.contains(address) }) else { return }
@@ -91,15 +89,21 @@ final class Bus {
 
  // MARK: - Private
 
- /// The ranges of the addressable devices attached to the bus that can be read from.
+ /// The ranges of the ``AddressableReadDevice``s attached to the bus.
  private let addressableReadDeviceRanges: [AddressRange]
 
- /// The ranges of the addressable devices attached to the bus that can be written to.
+ /// The ranges of the ``AddressableWriteDevice``s attached to the bus.
  private let addressableWriteDeviceRanges: [AddressRange]
 
- /// All of the addressable devices attached to the bus that can be read from.
+ /// All of the ``AddressableReadDevice``s attached to the bus.
  private let addressableReadDevices: [any AddressableReadDevice]
 
- /// All of the addressable devices attached to the bus that can be written to.
+ /// All of the ``AddressableWriteDevice``s attached to the bus.
  private let addressableWriteDevices: [any AddressableWriteDevice]
 }
+
+extension Bus: DirectMemoryAccessableReadDevice {
+ func dmaRead(from address: Address) -> Value {
+ read(from: address)
+ }
+}

Sources/SwiftNES/CartridgeConnector.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 /// A class that represents a connection to a cartridge.
 ///
 /// Instead of attaching the cartridge directly to the bus, a connector is used to allow for

Sources/SwiftNES/ControllerConnector.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 /// A controller that can be connected to a ``ControllerConnector``.
 public protocol Controller: AnyObject {
  /// Reads a single bit from the controller.

Sources/SwiftNES/Controllers/ControlPad.swift

@@ -20,8 +20,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
-
 /// A class that represents an NES Control Pad (NES-004).
 public final class ControlPad: Controller {
 

Sources/SwiftNES/DirectMemoryAccessController.swift

@@ -1,6 +1,6 @@
 // MIT License
 //
-// Copyright (c) 2020 Jerrod Putman
+// Copyright (c) 2023 Jerrod Putman
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -20,26 +20,119 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-import Foundation
+/// Errors that are thrown by the ``DirectMemoryAccessController``.
+enum DirectMemoryAccessControllerError: Error {
+ /// The ``DirectMemoryAccessController/readDevice`` was not assigned.
+ case readDeviceNotAssigned
+
+ /// The ``DirectMemoryAccessController/writeDevice`` was not assigned.
+ case writeDeviceNotAssigned
+}
 
-struct ObjectAttributeEntry {
- var y: UInt8
- var id: UInt8
- var attribute: UInt8
- var x: UInt8
+/// Represents a device that the ``DirectMemoryAccessController`` reads from.
+protocol DirectMemoryAccessableReadDevice: AnyObject {
+ /// Reads a value from the device at the specified address.
+ ///
+ /// - Parameter address: The ``Address`` of the device to read from.
+ /// - Returns: The ``Value`` stored at the address on the device.
+ func dmaRead(from address: Address) -> Value
 }
 
-var objectAttributeMemory: [ObjectAttributeEntry] = []
+/// Represents a device that the ``DirectMemoryAccessController`` writes to.
+protocol DirectMemoryAccessableWriteDevice: AnyObject {
+ /// Writes a value to the device at the specified address.
+ ///
+ /// - Parameter value: The ``Value`` to write to the device.
+ /// - Parameter address: The 8-bit address to write to on the device.
+ func dmaWrite(_ value: Value, to address: UInt8)
+}
 
-final class DirectMemoryAccessController {
+/// Represents the direct memory access controller of the NES.
+final class DirectMemoryAccessController: AddressableWriteDevice {
 
- init() {
- page = 0
- address = 0
- data = 0
+ // MARK: - Initializers
+
+ /// Initializes the controller.
+ ///
+ /// - Parameter address: The ``Address`` where the controller can be written to.
+ init(address: Address) {
+ self.addressRange = address...address
+
+ self.page = 0
+ self.address = 0
+ self.data = 0
  }
 
+
+ // MARK: - Getting the status of the controller
+
+ /// Whether or not a DMA transfer is in progress.
+ private(set) var isTransferInProgress = false
+
+
+ // MARK: - Transferring data
+
+ /// The device to read from during transfers.
+ weak var readDevice: (any DirectMemoryAccessableReadDevice)?
+
+ /// The device to write to during transfers.
+ weak var writeDevice: (any DirectMemoryAccessableWriteDevice)?
+
+ /// Clocks the controller.
+ ///
+ /// - Parameter cycleCount: The current cycle count of the hardware.
+ /// - Returns: Whether or not a transfer is in progress.
+ /// - Throws: A ``DirectMemoryAccessControllerError``.
+ func clock(cycleCount: UInt) throws -> Bool {
+ guard isTransferInProgress else { return false }
+
+ guard let readDevice else { throw DirectMemoryAccessControllerError.readDeviceNotAssigned }
+ guard let writeDevice else { throw DirectMemoryAccessControllerError.writeDeviceNotAssigned }
+
+ if syncCycle {
+ if cycleCount % 2 == 1 {
+ syncCycle = false
+ }
+ } else {
+ if cycleCount % 2 == 0 {
+ data = readDevice.dmaRead(from: UInt16(lo: address, hi: page))
+ } else {
+ writeDevice.dmaWrite(data, to: address)
+ address &+= 1
+
+ if address == 0 {
+ isTransferInProgress = false
+ syncCycle = true
+ }
+ }
+ }
+
+ return true
+ }
+
+
+ // MARK: - AddressableWriteDevice
+
+ let addressRange: AddressRange
+
+ func write(_ data: Value, to address: Address) {
+ page = data
+ self.address = 0
+ isTransferInProgress = true
+ }
+
+
+ // MARK: - Private
+
+ /// The page of memory where the current DMA transfer is occurring.
  private var page: UInt8
+
+ /// The address of memory, offset from the page, where the current DMA transfer is occurring.
  private var address: UInt8
+
+ /// The data that is currently being moved from the CPU to the PPU.
  private var data: Value
+
+ /// Whether or not the transfer should wait for synchronization.
+ private var syncCycle = true
 }