High-level wire implementation, complete with unit tests

SampleProjects/TestSomething/test/wire.cpp

@@ -0,0 +1,78 @@
+#include <ArduinoUnitTests.h>
+#include <Arduino.h>
+#include <Wire.h>
+using std::deque;
+
+unittest(begin_write_end) {
+    // master write buffer should be empty
+    deque<uint8_t>* mosi = Wire.getMosi(14);
+    assertEqual(0, mosi->size());
+
+    // write some random values to random slave
+    Wire.begin();
+    Wire.beginTransmission(14);
+    Wire.write(0x07);
+    Wire.write(0x0E);
+    Wire.endTransmission();
+
+    // check master write buffer values
+    assertEqual(2, mosi->size());
+    assertEqual(0x07, mosi->front());
+    mosi->pop_front();
+    assertEqual(0x0E, mosi->front());
+    mosi->pop_front();
+    assertEqual(0, mosi->size());
+}
+
+unittest(readTwo_writeOne) {
+    Wire.begin();
+    deque<uint8_t>* miso;
+    // place some values on random slaves' read buffers
+    miso = Wire.getMiso(19);
+    miso->push_back(0x07);
+    miso->push_back(0x0E);
+    miso = Wire.getMiso(34);
+    miso->push_back(1);
+    miso->push_back(4);
+    miso->push_back(7);
+
+    // check read buffers and read-related functions
+    assertEqual(0, Wire.requestFrom(19, 3));
+    assertEqual(2, Wire.requestFrom(19, 2));
+    assertEqual(2, Wire.available());
+    assertEqual(0x07, Wire.read());
+    assertEqual(1, Wire.available());
+    assertEqual(0x0E, Wire.read());
+    assertEqual(0, Wire.available());
+    assertEqual(3, Wire.requestFrom(34, 3));
+    assertEqual(3, Wire.available());
+    assertEqual(1, Wire.read());
+    assertEqual(2, Wire.available());
+    assertEqual(4, Wire.read());
+    assertEqual(1, Wire.available());
+    assertEqual(7, Wire.read());
+    assertEqual(0, Wire.available());
+
+    // write some values to different random slave
+    Wire.beginTransmission(47);
+    for (int i = 1; i < 4; i++) {
+        Wire.write(i * 2);
+    }
+    Wire.endTransmission();
+
+    // check master write buffer
+    deque<uint8_t>* mosi = Wire.getMosi(47);
+
+    assertEqual(3, mosi->size());
+    assertEqual(2, mosi->front());
+    mosi->pop_front();
+    assertEqual(2, mosi->size());
+    assertEqual(4, mosi->front());
+    mosi->pop_front();
+    assertEqual(1, mosi->size());
+    assertEqual(6, mosi->front());
+    mosi->pop_front();
+    assertEqual(0, mosi->size());
+}
+
+unittest_main()

cpp/arduino/Wire.h

@@ -1,138 +1,225 @@
+/*
+ * The Wire Library (https://www.arduino.cc/en/Reference/Wire)
+ * allows you to communicate with I2C/TWI devices. The general
+ * TWI protocol supports one "master" device and many "slave"
+ * devices that share the same two wires (SDA and SCL for data
+ * and clock respectively).
+ *
+ * You initialize the library by calling begin() as a master or
+ * begin(myAddress) as a slave (with an int from 8-127). In the
+ * initial mock implementation we support only the master role.
+ *
+ * To send bytes from a master to a slave, start with
+ * beginTransmission(slaveAddress), then use write(byte) to
+ * enqueue data, and finish with endTransmission().
+ *
+ * When a master wants to read, it starts with a call to
+ * requestFrom(slaveAddress, quantity) which blocks until the
+ * request finishes. The return value is either 0 (if the slave
+ * does not respond) or the number of bytes requested (which
+ * might be more than the number sent since reading is simply
+ * looking at a pin value at each clock tick).
+ *
+ * A master can write to or read from two or more slaves in
+ * quick succession (say, during one loop() function), so our
+ * mock needs to support preloading data to be read from multiple
+ * slaves and archive data sent to multiple slaves.
+ *
+ * In the mock, this is handled by having an array of wireData_t
+ * structures, each of which contains a deque for input and a
+ * deque for output. You can preload data to be read and you can
+ * look at a log of data that has been written.
+ */
 
 #pragma once
 
 #include <inttypes.h>
 #include "Stream.h"
+#include <cassert>
+#include <deque>
+using std::deque;
+
+const size_t SLAVE_COUNT = 128;
+const size_t BUFFER_LENGTH = 32;
+
+struct wireData_t {
+  uint8_t misoSize;          // bytes remaining for this read
+  uint8_t mosiSize;          // bytes included in this write
+  deque<uint8_t> misoBuffer; // master in, slave out
+  deque<uint8_t> mosiBuffer; // master out, slave in
+};
+
+// Some inspiration taken from
+// https://github.com/arduino/ArduinoCore-megaavr/blob/d2a81093ba66d22dbda14c30d146c231c5910734/libraries/Wire/src/Wire.cpp
+class TwoWire : public ObservableDataStream {
+private:
+  bool _didBegin = false;
+  wireData_t *in = nullptr;  // pointer to current slave for writing
+  wireData_t *out = nullptr; // pointer to current slave for reading
+  wireData_t slaves[SLAVE_COUNT];
 
-class TwoWire : public ObservableDataStream
-{
 public:
+  // constructor initializes internal data
   TwoWire() {
+    for (int i = 0; i < SLAVE_COUNT; ++i) {
+      slaves[i].misoSize = 0;
+      slaves[i].mosiSize = 0;
+    }
   }
 
   // https://www.arduino.cc/en/Reference/WireBegin
-  // Initiate the Wire library and join the I2C bus as a master or slave. This should normally be called only once.
-  void begin() {
-    isMaster = true;
-  }
-  void begin(int address) {
-    i2cAddress = address;
-    isMaster = false;
-  }
+  // Initiate the Wire library and join the I2C bus as a master or slave. This
+  // should normally be called only once.
+  void begin() { begin(0); }
   void begin(uint8_t address) {
-    begin((int)address);
-  }
-  void end() {
-    // TODO: implement
+    assert(address == 0);
+    _didBegin = true;
   }
+  void begin(int address) { begin((uint8_t)address); }
+  // NOTE: end() is not part of the published API so we ignore it
+  void end() {}
 
   // https://www.arduino.cc/en/Reference/WireSetClock
-  // This function modifies the clock frequency for I2C communication. I2C slave devices have no minimum working
-  // clock frequency, however 100KHz is usually the baseline.
-  void setClock(uint32_t) {
-    // TODO: implement?
-  }
+  // This function modifies the clock frequency for I2C communication. I2C slave
+  // devices have no minimum working clock frequency, however 100KHz is usually
+  // the baseline.
+  // Since the mock does not actually write pins we ignore this.
+  void setClock(uint32_t clock) {}
 
   // https://www.arduino.cc/en/Reference/WireBeginTransmission
-  // Begin a transmission to the I2C slave device with the given address. Subsequently, queue bytes for
-  // transmission with the write() function and transmit them by calling endTransmission().
-  void beginTransmission(int address) {
-    // TODO: implement
-  }
+  // Begin a transmission to the I2C slave device with the given address.
+  // Subsequently, queue bytes for transmission with the write() function and
+  // transmit them by calling endTransmission().
+  // For the mock we update our output to the proper destination.
   void beginTransmission(uint8_t address) {
-    beginTransmission((int)address);
+    assert(_didBegin);
+    assert(address > 0 && address < SLAVE_COUNT);
+    assert(out == nullptr);
+    out = &slaves[address];
+    out->mosiSize = 0;
   }
+  void beginTransmission(int address) { beginTransmission((uint8_t)address); }
 
   // https://www.arduino.cc/en/Reference/WireEndTransmission
-  // Ends a transmission to a slave device that was begun by beginTransmission() and transmits the bytes that were
-  // queued by write().
-  uint8_t endTransmission(uint8_t sendStop) {
-    // TODO: implement
+  // Ends a transmission to a slave device that was begun by beginTransmission()
+  // and transmits the bytes that were queued by write().
+  // In the mock we just leave the bytes there in the buffer
+  // to be read by the testing API and we ignore the sendStop.
+  uint8_t endTransmission(bool sendStop) {
+    assert(_didBegin);
+    assert(out);
+    out = nullptr;
     return 0; // success
   }
-  uint8_t endTransmission(void) {
-    return endTransmission((uint8_t)true);
-  }
+  uint8_t endTransmission(void) { return endTransmission(true); }
 
   // https://www.arduino.cc/en/Reference/WireRequestFrom
-  // Used by the master to request bytes from a slave device. The bytes may then be retrieved with the
-  // available() and read() functions.
-  uint8_t requestFrom(int address, int quantity, int stop) {
-    // TODO: implement
-    return 0; // number of bytes returned from the slave device
+  // Used by the master to request bytes from a slave device. The bytes may then
+  // be retrieved with the available() and read() functions.
+  uint8_t requestFrom(uint8_t address, size_t quantity, bool stop) {
+    assert(_didBegin);
+    assert(address > 0 && address < SLAVE_COUNT);
+    assert(quantity <= BUFFER_LENGTH);
+    in = &slaves[address];
+    // do we have enough data in the input buffer
+    if (quantity <= (in->misoBuffer).size()) { // enough data
+      in->misoSize = quantity;
+      return quantity;
+    } else { // not enough data
+      in->misoSize = 0;
+      in = nullptr;
+      return 0;
+    }
   }
   uint8_t requestFrom(int address, int quantity) {
-    int stop = true;
-    return requestFrom(address, quantity, stop);
-  }
-  uint8_t requestFrom(uint8_t address, uint8_t quantity) {
-    return requestFrom((int)address, (int)quantity);
+    return requestFrom((uint8_t)address, (size_t)quantity, true);
   }
-  uint8_t requestFrom(uint8_t address, uint8_t quantity, uint8_t stop) {
-    return requestFrom((int)address, (int)quantity, (int)stop);
-  }
-  uint8_t requestFrom(uint8_t, uint8_t, uint32_t, uint8_t, uint8_t) {
-    // TODO: implement
-    return 0;
+  uint8_t requestFrom(int address, int quantity, int stop) {
+    return requestFrom((uint8_t)address, (size_t)quantity, (bool)stop);
   }
 
   // https://www.arduino.cc/en/Reference/WireWrite
-  // Writes data from a slave device in response to a request from a master, or queues bytes for transmission from a
-  // master to slave device (in-between calls to beginTransmission() and endTransmission()).
+  // Writes data from a slave device in response to a request from a master, or
+  // queues bytes for transmission from a master to slave device (in-between
+  // calls to beginTransmission() and endTransmission()).
   size_t write(uint8_t value) {
-    // TODO: implement
-    return 0; // number of bytes written
+    assert(out);
+    assert(++(out->mosiSize) <= BUFFER_LENGTH);
+    (out->mosiBuffer).push_back(value);
+    return 1; // number of bytes written
+  }
+  size_t write(const char *str) {
+    return str == NULL ? 0 : write((const uint8_t *)str, String(str).length());
   }
-  size_t write(const char *str) { return str == NULL ? 0 : write((const uint8_t *)str, String(str).length()); }
   size_t write(const uint8_t *buffer, size_t size) {
     size_t n;
-    for (n = 0; size && write(*buffer++) && ++n; --size);
+    for (n = 0; size && write(*buffer++) && ++n; --size)
+      ;
     return n;
   }
-  size_t write(const char *buffer, size_t size) { return write((const uint8_t *)buffer, size); }
+  size_t write(const char *buffer, size_t size) {
+    return write((const uint8_t *)buffer, size);
+  }
   size_t write(unsigned long n) { return write((uint8_t)n); }
   size_t write(long n) { return write((uint8_t)n); }
   size_t write(unsigned int n) { return write((uint8_t)n); }
   size_t write(int n) { return write((uint8_t)n); }
 
   // https://www.arduino.cc/en/Reference/WireAvailable
-  // Returns the number of bytes available for retrieval with read(). This should be called on a master device after a
-  // call to requestFrom() or on a slave inside the onReceive() handler.
+  // Returns the number of bytes available for retrieval with read(). This
+  // should be called on a master device after a call to requestFrom() or on a
+  // slave inside the onReceive() handler.
   int available(void) {
-    // TODO: implement
-    return 0; // number of bytes available for reading
+    assert(in);
+    return in->misoSize;
   }
 
   // https://www.arduino.cc/en/Reference/WireRead
-  // Reads a byte that was transmitted from a slave device to a master after a call to requestFrom() or was transmitted
-  // from a master to a slave. read() inherits from the Stream utility class.
-  int read(void) {
-    // TODO: implement
-    return '\0'; // The next byte received
+  // Reads a byte that was transmitted from a slave device to a master after a
+  // call to requestFrom() or was transmitted from a master to a slave. read()
+  // inherits from the Stream utility class.
+  // In the mock we simply return the next byte from the input buffer.
+  uint8_t read(void) {
+    uint8_t value = peek();
+    --in->misoSize;
+    in->misoBuffer.pop_front();
+    return value; // The next byte received
   }
-  int peek(void) {
-    // TODO: implement
-    return 0;
+
+  // part of the Stream API
+  uint8_t peek(void) {
+    assert(in);
+    assert(0 < in->misoSize);
+    return in->misoBuffer.front(); // The next byte received
   }
+
+  // part of the Stream API
   void flush(void) {
-    // TODO: implement
+    // NOTE: commented out in the megaavr repository
+    // data already at the (mock) destination
   }
 
   // https://www.arduino.cc/en/Reference/WireOnReceive
-  // Registers a function to be called when a slave device receives a transmission from a master.
-  void onReceive( void (*callback)(int) ) {
-    // TODO: implement
-  }
+  // Registers a function to be called when a slave device receives a
+  // transmission from a master.
+  // We don't (yet) support the slave role in the mock
+  void onReceive(void (*callback)(int)) { assert(false); }
 
   // https://www.arduino.cc/en/Reference/WireOnRequest
-  // Register a function to be called when a master requests data from this slave device.
-  void onRequest( void (*callback)(void) ) {
-    // TODO: implement
-  }
+  // Register a function to be called when a master requests data from this
+  // slave device.
+  // We don't (yet) support the slave role in the mock
+  void onRequest(void (*callback)(void)) { assert(false); }
 
-private:
-  int i2cAddress;
-  bool isMaster = false;
+  // testing methods
+  bool didBegin() { return _didBegin; }
+
+  deque<uint8_t> *getMiso(uint8_t address) {
+    return &slaves[address].misoBuffer;
+  }
+  deque<uint8_t> *getMosi(uint8_t address) {
+    return &slaves[address].mosiBuffer;
+  }
 };
 
 extern TwoWire Wire;