Clean up timing, remove debug

python/samples/lcd1602.py

@@ -1,6 +1,10 @@
 """
-Example for LCD1602, in which a PCF8574 I/O expander drives a HD44780
+Example for LCD1602, in which a PCF8574 I/O expander drives a HD44780.
 Available from various vendors.
+
+Note that the modules require a 5V VCC; they don't function using the
+3.3V VCC of I2CDriver.
+
 """
 
 import sys
@@ -15,12 +19,7 @@ class HD44780:
         self.i2 = i2
         self.a = a
 
-        # Command (0) / Data (1) (aka RS) (D0)
-        # R/W                             (D1)
-        # Enable/CLK                      (D2) 
-        # Backlight control               (D3)
-
-        self.nybble(3)
+        self.nybble(3)  # Enter 4-bit mode
         self.nybble(3)
         self.nybble(3)
         self.nybble(2)
@@ -30,42 +29,38 @@ class HD44780:
         self.cmd(0x06)  # inc cursor to right when writing and don't scroll
         self.cmd(0x80)  # set cursor to row 1, column 1
 
-        time.sleep(.2)
-        self.data(0x42)
-
-        while 0:
-            self.port(0)
-            time.sleep(.1)
-            self.port(8)
-            time.sleep(.1)
-        # self.clear()
+        self.clear()
 
     def clear(self):
-        """ Blank / Reset LCD """
-        self.cmd(0x33) # $33 8-bit mode
-        self.cmd(0x32) # $32 8-bit mode
-        self.cmd(0x28) # $28 8-bit mode
-        self.cmd(0x0C | 3) # $0C 8-bit mode
-        self.cmd(0x06) # $06 8-bit mode
-        self.cmd(0x01) # $01 8-bit mode
+        """ Clear the screen """
+        self.cmd(0x01)
+        time.sleep(.003)
 
-    def port(self, *bb):
-        # Write byte to port
-        if 0:
-            self.i2.start(self.a, 0)
-            self.i2.write(bb)
-            self.i2.stop()
-            time.sleep(.000500)
-            time.sleep(.050)
-        else:
-            for b in bb:
-                self.i2.start(self.a, 0)
-                self.i2.write([b])
-                self.i2.stop()
-                time.sleep(.005000)
+    def show(self, line, text):
+        """ Send string to LCD. Newline wraps to second line"""
+        self.cmd({0:0x80, 1:0xc0}[line])
+        for c in text:
+            self.data(ord(c))
+
+    def cmd(self, b):
+        self.nybble(b >> 4)
+        self.nybble(b & 0xf)
+        time.sleep(.000053)
+
+    def data(self, b):
+        self.nybble(b >> 4, 1)
+        self.nybble(b & 0xf, 1)
+
+    # The PCF8574 outputs are connected to the HD44780
+    # pins as follows:
+
+    # P0    RS (0: command, 1: data)
+    # P1    R/W (0: write, 1: read)
+    # P2    Enable/CLK
+    # P3    Backlight control
+    # P4-7  D4-D7
 
     def nybble(self, n, rs = 0):
-        print("   nyb %x" % n)
         bl = 8 | rs
         self.port(
             bl | (n << 4),
@@ -73,29 +68,15 @@ class HD44780:
             bl | (n << 4)
         )
 
-    def cmd(self, b):
-        print("cmd %02x" % b)
-        self.nybble(b >> 4)
-        self.nybble(b & 0xf)
-        time.sleep(.004100)
-
-    def data(self, b):
-        print("DAT %02x" % b)
-        self.nybble(b >> 4, 1)
-        self.nybble(b & 0xf, 1)
-        time.sleep(.004100)
-
-    def message(self, text):
-        """ Send string to LCD. Newline wraps to second line"""
-
-        for char in text:
-            if char == '\n':
-                self.cmd(0xC0) # next line
-            else:
-                self.data(ord(char))
+    def port(self, *bb):
+        # Write bytes to port, setting the PCF8574 outputs
+        self.i2.start(self.a, 0)
+        self.i2.write(bb)
+        self.i2.stop()
 
 if __name__ == '__main__':
     i2 = I2CDriver(sys.argv[1])
-    i2.scan()
     d = HD44780(i2)
-    d.message("HELLO WORLD")
+    d.show(0, "HELLO WORLD")
+    time.sleep(.5)
+    d.show(1, "0123456789012345")