System.Hardware.PiLcd.UnicodeLcd

Displays Unicode text on an LCD. Only updates the parts of the LCD which have changed. Automatically manages custom characters, using the 5x8 fixed font for characters which are not built-in to the the LCD controller's ROM. Only eight distinct non-built-in characters can be on the display at any one time.

Only supports characters which are made up of a single code point. (In other words, combining marks are not supported.) If your input contains decomposed characters, consider using the unicode-transforms package to convert to Normalization Form C.

Displays up to 20x4 should be supported, although only 16x2 has been tested.

Creating an LCD

mkLcd :: LcdCallbacks -> LcdOptions -> IO Lcd

Given callbacks and options, creates an Lcd. Assumes the display has already been initialized via a call to lcdInitialize.

data Lcd

An opaque type representing an LCD.

lcdOptions :: Lcd -> LcdOptions

Returns the LcdOptions that were passed to mkLcd

data LcdOptions

Specifies the characteristics of the LCD.

Constructors

LcdOptions

Fields

• loLines :: !Int

  Number of lines

• loColumns :: !Int

  Number of columns

• loRomCode :: RomCode

  Built-in character set

• loCustomChars :: [(Char, [Word8])]

  Additional user-defined characters, beyond those in the 5x8 fixed font. Character is defined as 8 bytes, with data in least-significant 5 bits.

Instances

Eq LcdOptions

Methods

(==) :: LcdOptions -> LcdOptions -> Bool

(/=) :: LcdOptions -> LcdOptions -> Bool

Ord LcdOptions

Methods

compare :: LcdOptions -> LcdOptions -> Ordering

(<) :: LcdOptions -> LcdOptions -> Bool

(<=) :: LcdOptions -> LcdOptions -> Bool

(>) :: LcdOptions -> LcdOptions -> Bool

(>=) :: LcdOptions -> LcdOptions -> Bool

max :: LcdOptions -> LcdOptions -> LcdOptions

min :: LcdOptions -> LcdOptions -> LcdOptions

Read LcdOptions

Methods

readsPrec :: Int -> ReadS LcdOptions

readList :: ReadS [LcdOptions]

readPrec :: ReadPrec LcdOptions

readListPrec :: ReadPrec [LcdOptions]

Show LcdOptions

Methods

showsPrec :: Int -> LcdOptions -> ShowS

show :: LcdOptions -> String

showList :: [LcdOptions] -> ShowS

defaultLcdOptions :: LcdOptions

Defaults to 2 lines, 16 columns, ROM code A00, and no additional custom characters.

data RomCode

The HD44780U LCD controller comes in two different variants with different character ROMs. (See Table 4 on pages 17-18 of the HD44780U datasheet.) Unfortunately, as best as I can interpret this exchange with Adafruit customer support, Adafruit ships a mixture of A00 ROMs and A02 ROMs, depending on what's available at the moment. ("We take what's available or we don't sell LCDs.") This is a bit annoying, since there doesn't seem to be any way to query the HD44780U to find out which ROM it has. So, the user has to test their LCD and then specify which ROM they have.

Constructors

RomA00

RomA02

Instances

Bounded RomCode

Methods

minBound :: RomCode

maxBound :: RomCode

Enum RomCode

Methods

succ :: RomCode -> RomCode

pred :: RomCode -> RomCode

toEnum :: Int -> RomCode

fromEnum :: RomCode -> Int

enumFrom :: RomCode -> [RomCode]

enumFromThen :: RomCode -> RomCode -> [RomCode]

enumFromTo :: RomCode -> RomCode -> [RomCode]

enumFromThenTo :: RomCode -> RomCode -> RomCode -> [RomCode]

Eq RomCode

Methods

(==) :: RomCode -> RomCode -> Bool

(/=) :: RomCode -> RomCode -> Bool

Ord RomCode

Methods

compare :: RomCode -> RomCode -> Ordering

(<) :: RomCode -> RomCode -> Bool

(<=) :: RomCode -> RomCode -> Bool

(>) :: RomCode -> RomCode -> Bool

(>=) :: RomCode -> RomCode -> Bool

max :: RomCode -> RomCode -> RomCode

min :: RomCode -> RomCode -> RomCode

Read RomCode

Methods

readsPrec :: Int -> ReadS RomCode

readList :: ReadS [RomCode]

readPrec :: ReadPrec RomCode

readListPrec :: ReadPrec [RomCode]

Show RomCode

Methods

showsPrec :: Int -> RomCode -> ShowS

show :: RomCode -> String

showList :: [RomCode] -> ShowS

Displaying text

updateDisplay :: Lcd -> [Text] -> IO ()

Updates the contents of the LCD. You must specify the full contents of the screen, but only the parts which have changed since the last update are sent to the hardware. Converts from Unicode to the display's internal encoding, and automatically creates custom characters for characters which are not directly supported by the LCD.

Characters

getCharStatus :: Lcd -> Char -> CharStatus

Given a Unicode code point, determines whether the character is built-in, or is considered a custom character (of which only eight can be on the screen at any one time).

data CharStatus

Indicates whether a character can be found as a built-in or custom character

Constructors

CharBuiltin

character is supported by the LCD's ROM

CharCustom

not supported by ROM, but available in 5x8 fixed font, or in the user-defined characters specified in loCustomChars

CharNotFound

not available in ROM, 5x8 fixed font, or loCustomChars

Instances

Bounded CharStatus

Methods

minBound :: CharStatus

maxBound :: CharStatus

Enum CharStatus

Methods

succ :: CharStatus -> CharStatus

pred :: CharStatus -> CharStatus

toEnum :: Int -> CharStatus

fromEnum :: CharStatus -> Int

enumFrom :: CharStatus -> [CharStatus]

enumFromThen :: CharStatus -> CharStatus -> [CharStatus]

enumFromTo :: CharStatus -> CharStatus -> [CharStatus]

enumFromThenTo :: CharStatus -> CharStatus -> CharStatus -> [CharStatus]

Eq CharStatus

Methods

(==) :: CharStatus -> CharStatus -> Bool

(/=) :: CharStatus -> CharStatus -> Bool

Ord CharStatus

Methods

compare :: CharStatus -> CharStatus -> Ordering

(<) :: CharStatus -> CharStatus -> Bool

(<=) :: CharStatus -> CharStatus -> Bool

(>) :: CharStatus -> CharStatus -> Bool

(>=) :: CharStatus -> CharStatus -> Bool

max :: CharStatus -> CharStatus -> CharStatus

min :: CharStatus -> CharStatus -> CharStatus

Read CharStatus

Methods

readsPrec :: Int -> ReadS CharStatus

readList :: ReadS [CharStatus]

readPrec :: ReadPrec CharStatus

readListPrec :: ReadPrec [CharStatus]

Show CharStatus

Methods

showsPrec :: Int -> CharStatus -> ShowS

show :: CharStatus -> String

showList :: [CharStatus] -> ShowS

nativeChar :: Word8 -> Char

If for some reason you want to specify a character in the native 8-bit encoding of the LCD, instead of in Unicode, just call nativeChar on the 8-bit character value. This maps it to a region of the Private Use Area which is treated specially.