First pass at I2C bit bang implementation

HARDWARE.md

@@ -101,7 +101,7 @@
 | Servo/ESC PWM         | :green_heart:   | H     | See Motor table          | Uses PWM
 | Tone Out (Square Wave)| :green_heart:   | H     | `PulseIO::Buzzer`        | Except SAM3X. Uses PWM
 | I2C                   | :green_heart:   | H     | `I2C::Bus`               | Predetermined pins from IDE
-| I2C Bit Bang          | :heart:         | S     | `I2C::BitBang`           | Any pins
+| I2C Bit Bang          | :yellow_heart:  | S     | `I2C::BitBang`           | Any pins. No search yet. Maybe timing issues?
 | SPI                   | :green_heart:   | H     | `SPI::Bus`               | Predetermined pins from IDE
 | SPI Bit Bang          | :green_heart:   | S     | `SPI::BitBang`           | Any pins
 | UART                  | :green_heart:   | H     | `UART::Hardware`         | Except Atmega328, ATmega168

examples/display/ssd1306.rb

@@ -21,7 +21,12 @@
 # Only give the SDA pin of the I2C bus. SCL (clock) pin must be 
 # connected for it to work, but we don't need to control it.
 #
+
+# Board's hardware I2C interface on predetermined pins.
 bus = Denko::I2C::Bus.new(board: board, pin: :SDA)
+# Bit-banged I2C on any pins.
+# bus = Denko::I2C::BitBang.new(board: board, pins: {scl: 8, sda: 9})
+
 oled = Denko::Display::SSD1306.new(bus: bus, rotate: true)
 canvas = oled.canvas
 

examples/sensor/aht10.rb

@@ -1,11 +1,16 @@
 #
-# Example using AHT21 sensor over I2C, for temperature and humidity.
+# Example using AHT10 sensor over I2C, for temperature and humidity.
 #
 require 'bundler/setup'
 require 'denko'
 
 board = Denko::Board.new(Denko::Connection::Serial.new)
+
+# Board's hardware I2C interface on predetermined pins.
 bus = Denko::I2C::Bus.new(board: board, pin: :SDA)
+# Bit-banged I2C on any pins.
+# bus = Denko::I2C::BitBang.new(board: board, pins: {scl: 8, sda: 9})
+
 sensor = Denko::Sensor::AHT10.new(bus: bus) # address: 0x38 default
 
 # Get the shared #print_tph_reading method to print readings neatly.

lib/denko/board/i2c_bit_bang.rb

@@ -0,0 +1,42 @@
+module Denko
+  class Board
+    # CMD = 31
+    def i2c_bb_write(scl, sda, address, bytes, repeated_start=false)
+      bytes = [bytes] unless bytes.class == Array
+
+      # Use top bit of address to select stop condition (1), or repated start (0).
+      send_stop = repeated_start ? 0 : 1
+
+      write Message.encode  command:     31,
+                            pin:         scl,
+                            value:       sda,
+                            aux_message: pack(:uint8, 0x00) + 
+                                         pack(:uint8, address | (send_stop << 7)) +
+                                         pack(:uint8, bytes.length) +
+                                         pack(:uint8, bytes)
+    end
+
+    # CMD = 35
+    def i2c_bb_read(scl, sda, address, register, read_length, repeated_start=false)
+      # Use top bit of address to select stop condition (1), or repated start (0).
+      send_stop = repeated_start ? 0 : 1
+
+      # A register address starting register address can be given (up to 4 bytes)
+      if register
+        register = [register].flatten
+        raise ArgumentError, 'maximum 4 byte register address for I2C read' if register.length > 4
+        register_packed = pack(:uint8, [register.length] + register)
+      else
+        register_packed = pack(:uint8, [0])
+      end
+
+      write Message.encode  command:      32,
+                            pin:          scl,
+                            value:        sda,
+                            aux_message:  pack(:uint8, 0x00) + 
+                                          pack(:uint8, address | (send_stop << 7)) +
+                                          pack(:uint8, read_length) +
+                                          register_packed
+    end
+  end
+end

lib/denko/i2c.rb

@@ -1,6 +1,7 @@
 module Denko
   module I2C
     autoload :Bus,        "#{__dir__}/i2c/bus"
+    autoload :BitBang,    "#{__dir__}/i2c/bit_bang"
     autoload :Peripheral, "#{__dir__}/i2c/peripheral"
   end
 end

lib/denko/i2c/bit_bang.rb

@@ -0,0 +1,59 @@
+module Denko
+  module I2C
+    class BitBang
+      include Behaviors::MultiPin
+      include Behaviors::BusControllerAddressed
+      include Behaviors::Reader
+
+      def initialize_pins(options={})
+        require_pins :scl, :sda
+      end
+
+      attr_reader :found_devices
+
+      def after_initialize(options={})
+        super(options)
+        @found_devices = []
+
+        # Board will see we respond to #pin with pins[:sda], and provide updates 
+        unregister
+        register
+        bubble_callbacks
+      end
+
+      # Receive data coming from the SDA pin.
+      def pin
+        pins[:sda]
+      end
+
+      # def search
+      #   addresses = read_using -> { board.i2c_search }
+      #   @found_devices = addresses.split(":").map(&:to_i) if addresses
+      # end
+
+      def write(address, bytes, frequency=nil, repeated_start=false)
+        board.i2c_bb_write(pins[:scl], pins[:sda], address, bytes, repeated_start)
+      end
+
+      def _read(address, register, num_bytes, frequency=nil, repeated_start=false)
+        board.i2c_bb_read(pins[:scl], pins[:sda], address, register, num_bytes, repeated_start)
+      end
+
+      def bubble_callbacks
+        add_callback(:bus_controller) do |str|
+          if str && str.match(/\A\d+-/)
+            address, data = str.split("-", 2)
+            address = address.to_i
+
+            data = data.split(",").map(&:to_i)
+            data = nil if data.empty?
+
+            components.each do |component|
+              component.update(data) if component.address == address
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/denko_cli/packages.rb

@@ -29,6 +29,13 @@ class DenkoCLI::Generator
       "DenkoOneWire.cpp",
     ]
   },
+  i2c_bb: {
+    description: "Bit Bang I2C support",
+    directive: "DENKO_I2C_BB",
+    files: [
+      "DenkoI2CBB.cpp",
+    ]
+  },
   spi_bb: {
     description: "Bit Bang SPI support",
     directive: "DENKO_SPI_BB",

src/lib/Denko.cpp

@@ -185,6 +185,12 @@ void Denko::process() {
     case 28: spiRemoveListener();  break;
     #endif
 
+    // Implemented in DenkoI2CBB.cpp
+    #ifdef DENKO_I2C_BB
+    case 31: i2c_bb_write        ();  break;
+    case 32: i2c_bb_read         ();  break;
+    #endif
+
     // Implemented in DenkoI2C.cpp
     #ifdef DENKO_I2C
     case 33: i2cSearch           ();  break;

src/lib/Denko.h

@@ -246,4 +246,30 @@ class Denko {
       };
       SpiListener spiListeners[SPI_LISTENER_COUNT];
     #endif
+
+    // I2C Bit Bang Interface
+    #if defined(DENKO_I2C_BB)
+      uint8_t i2c_bb_scl_pin;
+      uint8_t i2c_bb_sda_pin;
+      uint8_t i2c_bb_quarter_period = 1;
+
+      // Internal stuff
+      void    i2c_bb_delay_quarter_period(); 
+      void    i2c_bb_delay_half_period();
+      void    i2c_bb_sda_high   ();
+      void    i2c_bb_sda_low    ();
+      void    i2c_bb_scl_high   ();
+      void    i2c_bb_scl_low    ();
+      void    i2c_bb_start      ();
+      void    i2c_bb_stop       ();
+      uint8_t i2c_bb_read_bit   ();
+      void    i2c_bb_write_bit  (uint8_t  bit );
+      uint8_t i2c_bb_read_byte  (bool     back);
+      int     i2c_bb_write_byte (uint8_t  data);
+      void    i2c_bb_init       (uint8_t scl, uint8_t sda);
+
+      // Remote exposed interface
+      void    i2c_bb_write      ();
+      void    i2c_bb_read       ();
+    #endif
 };

src/lib/DenkoDefines.h

@@ -11,6 +11,7 @@
 // #define DENKO_EEPROM
 // #define DENKO_ONE_WIRE
 // #define DENKO_TONE
+// #define DENKO_I2C_BB
 // #define DENKO_SPI_BB
 // #define DENKO_I2C
 // #define DENKO_SPI