Adafruit LCD example

_oasis

@@ -17,4 +17,10 @@ Executable "wpi-button-example"
   Path:         examples/
   BuildTools:   ocamlbuild
   MainIs:       button.ml
-  BuildDepends: WiringPi,unix
+  BuildDepends: WiringPi,unix
+
+Executable "adafruit-lcd-example"
+  Path:         examples/
+  BuildTools:   ocamlbuild
+  MainIs:       lcd.ml
+  BuildDepends: WiringPi,unix

examples/lcd.ml

@@ -0,0 +1,139 @@
+(** An example with Adafruit character LCD, HD44780. *)
+open Gpio3
+
+(** Parameters *)
+type mono_lcd = {
+    columns: int;
+    rows: int;
+    rs: pin;
+    en: pin;
+    d4: pin;
+    d5: pin;
+    d6: pin;
+    d7: pin
+}
+let lcd = {
+    columns = 16;
+    rows = 2;
+    rs = GPIO20;
+    en = GPIO16;
+    d4 = GPIO19;
+    d5 = GPIO5;
+    d6 = GPIO11;
+    d7 = GPIO10;
+}
+
+(** MAGIC NUMBERS *)
+(* Commands *)
+let _lcd_cleardisplay        = (0x01)
+let _lcd_returnhome          = (0x02)
+let _lcd_entrymodeset        = (0x04)
+let _lcd_displaycontrol      = (0x08)
+let _lcd_cursorshift         = (0x10)
+let _lcd_functionset         = (0x20)
+let _lcd_setcgramaddr        = (0x40)
+let _lcd_setddramaddr        = (0x80)
+
+(* Entry flags *)
+let _lcd_entryleft           = (0x02)
+let _lcd_entryshiftdecrement = (0x00)
+
+(* Control flags *)
+let _lcd_displayon           = (0x04)
+let _lcd_cursoron            = (0x02)
+let _lcd_cursoroff           = (0x00)
+let _lcd_blinkon             = (0x01)
+let _lcd_blinkoff            = (0x00)
+
+(* Move flags *)
+let _lcd_displaymove         = (0x08)
+let _lcd_moveright           = (0x04)
+let _lcd_moveleft            = (0x00)
+
+(* Function set flags *)
+let _lcd_4bitmode            = (0x00)
+let _lcd_2line               = (0x08)
+let _lcd_1line               = (0x00)
+let _lcd_5x8dots             = (0x00)
+
+(* Offset for up to 4 rows. *)
+let _lcd_row_offsets = [|0x00; 0x40; 0x14; 0x54|]
+
+let pulse_enable lcd =
+  digital_write lcd.en LOW;
+  (* 1 microsec pause *)
+  Unix.sleepf(0.0000001);
+  digital_write lcd.en HIGH;
+  Unix.sleepf(0.0000001);
+  digital_write lcd.en LOW;
+  Unix.sleepf(0.00001)
+
+(** write 8 bits of data *)
+let write8 lcd ?(char_mode=false) value =
+  (* one ms delay to prevent writing too quickly *)
+  Unix.sleepf(0.001);
+  let char_mode_value = if char_mode then HIGH else LOW in
+  digital_write lcd.rs char_mode_value;
+  let val_of_int i = if i > 0 then HIGH else LOW in
+  let ival = Char.code value in
+  (* write the UPPER 4 bits (in reverse order) *)
+  digital_write lcd.d4 (val_of_int ((ival lsr 4) land 1));
+  digital_write lcd.d5 (val_of_int ((ival lsr 5) land 1));
+  digital_write lcd.d6 (val_of_int ((ival lsr 6) land 1));
+  digital_write lcd.d7 (val_of_int ((ival lsr 7) land 1));
+  pulse_enable lcd;
+  (* write the LOWER 4 bits *)
+  digital_write lcd.d4 (val_of_int (ival land 1));
+  digital_write lcd.d5 (val_of_int ((ival lsr 1) land 1));
+  digital_write lcd.d6 (val_of_int ((ival lsr 2) land 1));
+  digital_write lcd.d7 (val_of_int ((ival lsr 3) land 1));
+  pulse_enable lcd
+
+(** same as [write8] but write an int (must be within the range) *)
+let write8_unsafe lcd ?(char_mode=false) ival =
+  write8 lcd ~char_mode (Char.unsafe_chr ival)
+
+let setup lcd =
+  Gpio3.setup ();
+  pin_mode lcd.rs OUT;
+  pin_mode lcd.en OUT;
+  pin_mode lcd.d4 OUT;
+  pin_mode lcd.d5 OUT;
+  pin_mode lcd.d6 OUT;
+  pin_mode lcd.d7 OUT;
+  (* MAGIC *)
+  write8_unsafe lcd 0x33;
+  write8_unsafe lcd 0x32;
+  (* set up some stuff *)
+  let displayctrl = _lcd_displayon lor _lcd_cursoroff lor _lcd_blinkoff in
+  let displayfn = _lcd_4bitmode lor _lcd_1line lor _lcd_2line lor _lcd_5x8dots in
+  let displaymode = _lcd_entryleft lor _lcd_entryshiftdecrement in
+  write8_unsafe lcd (displayctrl lor _lcd_displaycontrol);
+  write8_unsafe lcd (displayfn lor _lcd_functionset);
+  write8_unsafe lcd (displaymode lor _lcd_entrymodeset);
+  Unix.sleepf(0.003)
+
+let clear lcd =
+  write8_unsafe lcd _lcd_cleardisplay;
+  Unix.sleepf(0.003)
+
+let shift_left lcd =
+  write8_unsafe lcd (_lcd_cursorshift lor _lcd_displaymove lor _lcd_moveleft)
+
+let shift_right lcd =
+  write8_unsafe lcd (_lcd_cursorshift lor _lcd_displaymove lor _lcd_moveright)
+
+let set_position lcd x y =
+  let c = x mod lcd.columns in
+  let r = y mod lcd.rows in
+  if (c < 0 || r < 0) then failwith "Lcd.set_position: Negative row or column";
+  write8_unsafe lcd (_lcd_setddramaddr lor (c + _lcd_row_offsets.(r)))
+
+let write_bytes lcd bts =
+  Bytes.iter (fun c -> write8 lcd c ~char_mode:true) bts
+
+let _ =
+  setup lcd;
+  clear lcd;
+  set_position lcd 0 0;
+  write_bytes lcd (Bytes.of_string "Hello, world.")