Add support for pycom devices

README.md

@@ -10,19 +10,20 @@ on the pyboard.
 Files
 =====
 
-| File                          | Description                           |
-| -----                         | -----------                           |
-| lcd.py                        | Core logic                            |
-| i2c_lcd.pyb                   | Linux I2C HAL                         |
-| pyb_gpio_lcd.py               | Pyboard GPIO HAL                      |
-| pyb_gpio_lcd_test8.py         | Pyboard test using 8-bit GPIO         |
-| pyb_gpio_lcd_test.py          | Pyboard test using 4-bit GPIO         |
-| pyb_i2c_adafruit_lcd.py       | Pyboard I2C HAL for Adafruit backpack |
-| pyb_i2c_adafruit_lcd_test.py  | Test for Adafruit backpack            |
-| pyb_i2c_lcd.py                | Pyboard I2C HAL for PCF8574 backpack  |
-| pyb_i2c_lcd_test.py           | Test for PCF8574 backpack             |
-| nodemcu_gpio_lcd.py           | NodeMCU GPIO HAL                      |
-| nodemcu_gpio_lcd_test.py      | NodeMCU test using 4-bit GPIO         |
+| File                          | Description                               |
+| -----                         | -----------                               |
+| lcd.py                        | Core logic                                |
+| i2c_lcd.pyb                   | Linux I2C HAL                             |
+| pyb_gpio_lcd.py               | Pyboard GPIO HAL                          |
+| pyb_gpio_lcd_test8.py         | Pyboard test using 8-bit GPIO             |
+| pyb_gpio_lcd_test.py          | Pyboard test using 4-bit GPIO             |
+| pyb_i2c_adafruit_lcd.py       | Pyboard I2C HAL for Adafruit backpack     |
+| pyb_i2c_adafruit_lcd_test.py  | Test for Adafruit backpack                |
+| pyb_i2c_lcd.py                | Pyboard I2C HAL for PCF8574 backpack      |
+| pyb_i2c_lcd_test.py           | Test for PCF8574 backpack                 |
+| nodemcu_gpio_lcd.py           | NodeMCU GPIO HAL                          |
+| nodemcu_gpio_lcd_test.py      | NodeMCU test using 4-bit GPIO             |
+| pycom_i2c_lcd.py              | Pycom boards I2C HAL for PCF8574 backpack |
 
 
 The files which end in _test.py are examples which show how the corresponding

lcd/pycom_i2c_lcd.py

@@ -0,0 +1,92 @@
+"""Implements a character based lcd connected via PCF8574 on i2c."""
+
+from lcd_api import LcdApi
+from machine import I2C
+import utime
+
+DEFAULT_I2C_ADDR = 0x3f
+
+# Defines shifts or masks for the various LCD line attached to the PCF8574
+
+MASK_RS = 0x01
+MASK_RW = 0x02
+MASK_E = 0x04
+SHIFT_BACKLIGHT = 3
+SHIFT_DATA = 4
+
+
+class I2cLcd(LcdApi):
+    """Implements a character based lcd connected via PCF8574 on i2c."""
+
+    def __init__(self, i2c, i2c_addr, num_lines, num_columns):
+        self.i2c = i2c
+        self.i2c_addr = i2c_addr
+        self.write(self.i2c_addr, 0)
+        utime.sleep_ms(20)  # Allow LCD time to powerup
+        # Send reset 3 times
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        utime.sleep_ms(5)  # need to utime.sleep_ms at least 4.1 msec
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        utime.sleep_ms(1)
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        utime.sleep_ms(1)
+        # Put LCD into 4 bit mode
+        self.hal_write_init_nibble(self.LCD_FUNCTION)
+        utime.sleep_ms(1)
+        LcdApi.__init__(self, num_lines, num_columns)
+        cmd = self.LCD_FUNCTION
+        if num_lines > 1:
+            cmd |= self.LCD_FUNCTION_2LINES
+        self.hal_write_command(cmd)
+
+    def write(self, address, byte):
+        self.i2c.writeto(address, bytes([byte]))
+
+    def hal_write_init_nibble(self, nibble):
+        """Writes an initialization nibble to the LCD.
+
+
+        This particular function is only used during intiialization.
+        """
+        byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA
+        self.write(self.i2c_addr, byte | MASK_E)
+        self.write(self.i2c_addr, byte)
+
+    def hal_backlight_on(self):
+        """Allows the hal layer to turn the backlight on."""
+        self.write(self.i2c_addr, 1 << SHIFT_BACKLIGHT)
+
+    def hal_backlight_off(self):
+        """Allows the hal layer to turn the backlight off."""
+        self.write(self.i2c_addr, 0)
+
+    def hal_write_command(self, cmd):
+        """Writes a command to the LCD.
+
+        Data is latched on the falling edge of E.
+        """
+        byte = ((self.backlight << SHIFT_BACKLIGHT) |
+                (((cmd >> 4) & 0x0f) << SHIFT_DATA))
+        self.write(self.i2c_addr, byte | MASK_E)
+        self.write(self.i2c_addr, byte)
+        byte = ((self.backlight << SHIFT_BACKLIGHT) |
+                ((cmd & 0x0f) << SHIFT_DATA))
+        self.write(self.i2c_addr, byte | MASK_E)
+        self.write(self.i2c_addr, byte)
+        if cmd <= 3:
+            # The home and clear commands require a worst
+            # case delay of 4.1 msec
+            utime.sleep_ms(5)
+
+    def hal_write_data(self, data):
+        """Write data to the LCD."""
+        byte = (MASK_RS |
+                (self.backlight << SHIFT_BACKLIGHT) |
+                (((data >> 4) & 0x0f) << SHIFT_DATA))
+        self.write(self.i2c_addr, byte | MASK_E)
+        self.write(self.i2c_addr, byte)
+        byte = (MASK_RS |
+                (self.backlight << SHIFT_BACKLIGHT) |
+                ((data & 0x0f) << SHIFT_DATA))
+        self.write(self.i2c_addr, byte | MASK_E)
+        self.write(self.i2c_addr, byte)