Refactor Raspberry Pi GPIO and add GPIO mock

pkg/raspberry_pi/lib/raspberry_pi.dart

Index: pkg/raspberry_pi/lib/raspberry_pi.dart
diff --git a/pkg/raspberry_pi/lib/raspberry_pi.dart b/pkg/raspberry_pi/lib/raspberry_pi.dart
index d0a8df0fdfe1734c3b51483b878361a8b2771fdc..9734327377fe91aaa21173298b66b207abe22677 100644
--- a/pkg/raspberry_pi/lib/raspberry_pi.dart
+++ b/pkg/raspberry_pi/lib/raspberry_pi.dart
@@ -5,9 +5,15 @@
 /// Library for the basic Raspberry Pi features.
 library raspberry_pi;
 
+import 'dart:fletch.ffi';
 import 'dart:typed_data';
 
 import 'package:file/file.dart';
+import 'package:gpio/gpio.dart' as gpio;
+
+// Foreign functions used.
+final ForeignFunction _open = ForeignLibrary.main.lookup('open');
+final ForeignFunction _mmap = ForeignLibrary.main.lookup('mmap');
 
 /// Possible modes of the on-board LEDs
 enum OnboardLEDMode {
@@ -23,6 +29,34 @@ enum OnboardLEDMode {
 
 /// Class for accessing Raspberry Pi features.
 ///
+/// Use GPIO through the memory mapped interface:
+///
+/// ```
+/// import 'package:raspberry_pi/raspberry_pi.dart';
+/// import 'package:gpio/gpio.dart';
+///
+/// main() {
+///   RaspberryPi pi = new RaspberryPi();
+///   GPIO gpio = pi.memoryMappedGPIO; // Selecting memory mapped GPIO.
+///   gpio.setMode(4, Mode.output);
+///   gpio.setPin(4, true);
+/// }
+/// ```
+///
+/// Use GPIO through the sysfs interface:
+///
+/// ```
+/// import 'package:raspberry_pi/raspberry_pi.dart';
+/// import 'package:gpio/gpio.dart';
+///
+/// main() {
+///   RaspberryPi pi = new RaspberryPi();
+///   GPIO gpio = pi.sysfsGPIO; // Selecting sysfs GPIO.
+///   gpio.setMode(4, Mode.output);
+///   gpio.setPin(4, true);
+/// }
+/// ```
+///
 /// Change the activity LED to heartbeat mode:
 ///
 /// ```
@@ -49,10 +83,176 @@ enum OnboardLEDMode {
 /// }
 /// ```
 class RaspberryPi {
+  /// The number of GPIO pins on the Raspberry Pi 2.
+  static const int gpioPins = 54;
+  var _memoryMappedGPIO;
+  var _sysfsGPIO;
+
   /// Provide access to the on-board LEDs.
   final OnBoardLEDs leds = new OnBoardLEDs._();
 
   RaspberryPi();
+
+  get memoryMappedGPIO {
+    if (_memoryMappedGPIO == null) {
+      _memoryMappedGPIO = new PiMemoryMappedGPIO();
+    }
+    return _memoryMappedGPIO;
+  }
+
+  get sysfsGPIO {
+    if (_sysfsGPIO == null) {
+      _sysfsGPIO = new gpio.SysfsGPIO(gpioPins);
+    }
+    return _sysfsGPIO;
+
+  }
+}
+
+/// Pull-up/down resistor state.
+enum PullUpDown {
+  floating,
+  pullDown,
+  pullUp,
+}
+
+/// Provide GPIO access on Raspberry Pi using direct memory access.
+///
+/// The following code shows how to turn on GPIO pin 4:
+///
+/// ```
+/// PiMemoryMappedGPIO gpio = new PiMemoryMappedGPIO();
+/// gpio.setMode(4, Mode.output);
+/// gpio.setPin(4, true));
+/// ```
+///
+/// The following code shows how to read GPIO pin 17:
+///
+/// ```
+/// PiMemoryMappedGPIO gpio = new PiMemoryMappedGPIO();
+/// gpio.setMode(17, Mode.input);
+/// print(gpio.getPin(17));
+/// ```
+class PiMemoryMappedGPIO extends gpio.GPIOBase {
+  // See datasheet:
+  // https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
+
+  // Raspberry Pi model 1 (A/A+/B)
+  // BCM2708 / BCM 2835
+
+  // Raspberry Pi model 2
+  // BCM2709 / BCM 2836
+
+  // Peripherals base address.
+  static const int _baseAddressModel1 = 0x20000000;
+  static const int _baseAddressModel2 = 0x3F000000;
+  static const int _baseAddressGPIOOffset = 0x00200000;
+
+  // Size of the peripherals area.
+  static const int _blockSize = 4096;
+
+  // Offsets (in bytes) to various areas.
+  static const int _gpioFunctionSelectBase = 0 << 2;
+  static const int _gpioOutputSetBase = 7 << 2;
+  static const int _gpioOutputClearBase = 10 << 2;
+  static const int _gpioPinLevelBase = 13 << 2;
+  static const int _gpioPullUpPullDown = 37 << 2;
+  static const int _gpioPullUpPullDownClockBase = 38 << 2;
+
+  // All alternative functions are mapped to `Mode.other` for now.
+  static const _functionToMode =
+      [gpio.Mode.input, gpio.Mode.output,
+       gpio.Mode.other, gpio.Mode.other,
+       gpio.Mode.other, gpio.Mode.other, gpio.Mode.other];
+
+  int _fd;  // File descriptor for /dev/mem.
+  ForeignPointer _addr;
+  ForeignMemory _mem;
+
+  PiMemoryMappedGPIO(): super(RaspberryPi.gpioPins) {
+    // From /usr/include/x86_64-linux-gnu/bits/fcntl-linux.h.
+    const int oRDWR = 02;  // O_RDWR

[wibling, 2015/10/05 07:43:37]

NIT: Shouldn't we keep these as O_RDWR to make it clear they are not variables?

+    // Found from C code 'printf("%x\n", O_SYNC);'.
+    const int oSync = 0x101000;  // O_SYNC
+
+    // Open /dev/mem to get to the physical memory.
+    var devMem = new ForeignMemory.fromStringAsUTF8('/dev/mem');
+    _fd = _open.icall$2Retry(devMem, oRDWR | oSync);
+    if (_fd < 0) {
+      throw new gpio.GPIOException("Failed to open '/dev/mem'", Foreign.errno);
+    }
+    devMem.free();
+
+    // From /usr/include/x86_64-linux-gnu/bits/mman-linux.h.
+    const int protRead = 0x1;  // PROT_READ.

[wibling, 2015/10/05 07:43:37]

Ditto.

+    const int protWrite = 0x2;  // PROT_WRITE.
+    const int mapShared = 0x01;  // MAP_SHARED.
+
+    _addr = _mmap.pcall$6(0, _blockSize, protRead | protWrite, mapShared,
+                          _fd, _baseAddressModel2 + _baseAddressGPIOOffset);
+    _mem = new ForeignMemory.fromAddress(_addr.address, _blockSize);
+  }
+
+  void setMode(int pin, gpio.Mode mode) {
+    checkPinRange(pin);
+    // GPIO function select registers each have 3 bits for 10 pins.
+    var fsel = (pin ~/ 10);
+    var shift = (pin % 10) * 3;
+    var function = mode == gpio.Mode.input ? 0 : 1;
+    var offset = _gpioFunctionSelectBase + (fsel << 2);
+    var value = _mem.getUint32(offset);
+    value = (value & ~(0x07 << shift)) | function << shift;
+    _mem.setUint32(offset, value);
+  }
+
+  gpio.Mode getMode(int pin) {
+    checkPinRange(pin);
+    // GPIO function select registers each have 3 bits for 10 pins.
+    var fsel = (pin ~/ 10);
+    var shift = (pin % 10) * 3;
+    var offset = _gpioFunctionSelectBase + (fsel << 2);
+    var function = (_mem.getUint32(offset) >> shift) & 0x07;
+    return _functionToMode[function];
+  }
+
+  void setPin(int pin, bool value) {
+    checkPinRange(pin);

[wibling, 2015/10/05 07:43:37]

NIT: Could enforce mode and fail on mismatch.

+    // GPIO output set and output clear registers each have 1 bits for 32 pins.

[wibling, 2015/10/05 07:43:37]

NIT: bits -> bit

+    int register = pin ~/ 32;
+    int shift = pin % 32;
+    if (value) {
+      _mem.setUint32(_gpioOutputSetBase + (register << 2), 1 << shift);
+    } else {
+      _mem.setUint32(_gpioOutputClearBase + (register << 2), 1 << shift);
+    }
+  }
+
+  bool getPin(int pin) {
+    checkPinRange(pin);
+    // GPIO pin level registers each have 1 bits for 32 pins.

[wibling, 2015/10/05 07:43:37]

NIT: bits -> bit

+    int register = pin ~/ 32;
+    int shift = pin % 32;
+    return
+        (_mem.getUint32(_gpioPinLevelBase + (register << 2)) & 1 << shift) != 0;
+  }
+
+  /// Set the floating/pull-up/pull-down state of [pin].
+  ///
+  /// Use `0` for floating, `1` for pull down and `2` for pull-up.
+  void setPullUpDown(int pin, PullUpDown pullUpDown) {
+    checkPinRange(pin);
+    int register = pin ~/ 32;
+    int shift = pin % 32;
+    // First set the value in the update register.
+    _mem.setUint32(_gpioPullUpPullDown, pullUpDown.index);
+    sleep(1);  // Datasheet says: "Wait for 150 cycles".
+    // Then set the clock bit.
+    _mem.setUint32(_gpioPullUpPullDownClockBase + (register << 2), 1 << shift);
+    sleep(1);  // Datasheet says: "Wait for 150 cycles".
+    // Clear value and clock bit.
+    _mem.setUint32(_gpioPullUpPullDown, 0);
+    _mem.setUint32(_gpioPullUpPullDownClockBase + (register << 2), 0);
+  }
 }
 
 // The on-board LEDs.