Circuitpython port (#26)

* Made it work in circuitpython.
* Made it work in circuitpython.
* Switched to UNIX EOL.
* Converted to Unix EOL.
* Made it work in circuitpython.
* Implemented hal_sleep_us
* Made it work in circuitpython.
Changed to more descriptive variable name.
* Tabs to spaces.

Author: TarjanPeter

lcd/circuitpython_i2c_lcd.py

@@ -0,0 +1,86 @@
+"""Implements a HD44780 character LCD connected via PCF8574 on I2C.
+   This was tested with: https://www.wemos.cc/product/d1-mini.html"""
+
+from lcd_api import LcdApi
+import busio
+from time import sleep
+
+# The PCF8574 has a jumper selectable address: 0x20 - 0x27
+DEFAULT_I2C_ADDR = 0x27
+
+# 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 HD44780 character 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.i2c.writeto(self.i2c_addr, bytearray([0]))
+        sleep(0.02)   # Allow LCD time to powerup
+		# Send reset 3 times
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep(0.005)    # need to delay at least 4.1 msec
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep(0.001)
+        self.hal_write_init_nibble(self.LCD_FUNCTION_RESET)
+        sleep(0.001)
+        # Put LCD into 4 bit mode
+        self.hal_write_init_nibble(self.LCD_FUNCTION)
+        sleep(0.001)
+        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 hal_write_init_nibble(self, nibble):
+        """Writes an initialization nibble to the LCD.
+
+        This particular function is only used during initialization.
+        """
+        byte = ((nibble >> 4) & 0x0f) << SHIFT_DATA
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+
+    def hal_backlight_on(self):
+        """Allows the hal layer to turn the backlight on."""
+        self.i2c.writeto(self.i2c_addr, bytearray([1 << SHIFT_BACKLIGHT]))
+
+    def hal_backlight_off(self):
+        """Allows the hal layer to turn the backlight off."""
+        self.i2c.writeto(self.i2c_addr, bytearray([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.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        byte = ((self.backlight << SHIFT_BACKLIGHT) | ((cmd & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        if cmd <= 3:
+            # The home and clear commands require a worst case delay of 4.1 msec
+            sleep(0.005)
+
+    def hal_write_data(self, data):
+        """Write data to the LCD."""
+        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | (((data >> 4) & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+        byte = (MASK_RS | (self.backlight << SHIFT_BACKLIGHT) | ((data & 0x0f) << SHIFT_DATA))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte | MASK_E]))
+        self.i2c.writeto(self.i2c_addr, bytearray([byte]))
+
+    def hal_sleep_us(self, usecs):
+        """Sleep for some time (given in microseconds)."""
+        sleep(float(usecs)/1e6)

lcd/circuitpython_i2c_lcd_test.py

@@ -0,0 +1,80 @@
+"""Implements a HD44780 character LCD connected via PCF8574 on I2C in CircuitPython.
+   This was tested with the Adafruit Trinket M0
+   https://www.adafruit.com/product/3500"""
+
+import board
+import busio
+from time import sleep, monotonic
+from circuitpython_i2c_lcd import I2cLcd
+
+# The PCF8574 has a jumper selectable address: 0x20 - 0x27
+DEFAULT_I2C_ADDR = 0x27
+
+def test_main():
+    """Test function for verifying basic functionality."""
+    print("Running test_main")
+    i2c = busio.I2C(board.SCL, board.SDA)
+
+    # circuitpython seems to require locking the i2c bus
+    while i2c.try_lock():
+        pass
+
+    # 2 lines, 16 characters per line
+    lcd = I2cLcd(i2c, DEFAULT_I2C_ADDR, 2, 16)
+
+    # smiley faces as custom characters
+    happy = bytearray([0x00,0x0A,0x00,0x04,0x00,0x11,0x0E,0x00])
+    sad = bytearray([0x00,0x0A,0x00,0x04,0x00,0x0E,0x11,0x00])
+    grin = bytearray([0x00,0x00,0x0A,0x00,0x1F,0x11,0x0E,0x00])
+    shock = bytearray([0x0A,0x00,0x04,0x00,0x0E,0x11,0x11,0x0E])
+    meh = bytearray([0x00,0x0A,0x00,0x04,0x00,0x1F,0x00,0x00])
+    angry = bytearray([0x11,0x0A,0x11,0x04,0x00,0x0E,0x11,0x00])
+    tongue = bytearray([0x00,0x0A,0x00,0x04,0x00,0x1F,0x05,0x02])
+    lcd.custom_char(0, happy)
+    lcd.custom_char(1, sad)
+    lcd.custom_char(2, grin)
+    lcd.custom_char(3, shock)
+    lcd.custom_char(4, meh)
+    lcd.custom_char(5, angry)
+    lcd.custom_char(6, tongue)
+
+    lcd.putstr("It works!\nSecond line")
+    sleep(3)
+    lcd.clear()
+    lcd.putstr("Custom chars:\n")
+    for i in range(7):
+        lcd.putchar(" ")
+        lcd.putchar(chr(i))
+        sleep(1)
+
+    sleep(3)
+    lcd.clear()
+    count = 0
+
+    while True:
+        lcd.move_to(0, 0)
+        lcd.putstr("%7d" % monotonic())
+        sleep(1)
+        count += 1
+        if count % 10 == 3:
+            print("Turning backlight off")
+            lcd.backlight_off()
+        if count % 10 == 4:
+            print("Turning backlight on")
+            lcd.backlight_on()
+        if count % 10 == 5:
+            print("Turning display off")
+            lcd.display_off()
+        if count % 10 == 6:
+            print("Turning display on")
+        if count % 10 == 7:
+            print("Turning display & backlight off")
+            lcd.backlight_off()
+            lcd.display_off()
+        if count % 10 == 8:
+            print("Turning display & backlight back on")
+            lcd.backlight_on()
+            lcd.display_on()
+
+#if __name__ == "__main__":
+test_main()

lcd/lcd_api.py

@@ -158,10 +158,10 @@ def custom_char(self, location, charmap):
         """
         location &= 0x7
         self.hal_write_command(self.LCD_CGRAM | (location << 3))
-        time.sleep_us(40)
+        self.hal_sleep_us(40)
         for i in range(8):
             self.hal_write_data(charmap[i])
-            time.sleep_us(40)
+            self.hal_sleep_us(40)
         self.move_to(self.cursor_x, self.cursor_y)
 
     def hal_backlight_on(self):
@@ -193,3 +193,7 @@ def hal_write_data(self, data):
         function.
         """
         raise NotImplementedError
+
+    def hal_sleep_us(self, usecs):
+        """Sleep for some time (given in microseconds)."""
+        time.sleep_us(usecs)