clerk 0.4.0

A fully featured hardware agnostic HD44780 LCD controlling library.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158

bitflags! {
    struct EntryModeFlags: u8 {
        const ENTRY_MODE            = 0b0000_0100;
        const CURSOR_MOVE_INCREMENT = 0b0000_0010;
        const DISPLAY_SHIFT_ON      = 0b0000_0001;
        const CURSOR_MOVE_DECREMENT = 0b0000_0000;
        const DISPLAY_SHIFT_OFF     = 0b0000_0000;
    }
}

/// Enumeration of possible methods to move.
#[derive(Clone, Copy)]
pub enum MoveDirection {
    /// Moves right.
    Increment,
    /// Moves left.
    Decrement,
}

impl From<MoveDirection> for EntryModeFlags {
    fn from(direction: MoveDirection) -> Self {
        match direction {
            MoveDirection::Increment => EntryModeFlags::CURSOR_MOVE_INCREMENT,
            MoveDirection::Decrement => EntryModeFlags::CURSOR_MOVE_DECREMENT,
        }
    }
}

/// Enumeration to set display shift.
#[derive(Clone, Copy)]
pub enum DisplayShift {
    On,
    Off,
}

impl From<DisplayShift> for EntryModeFlags {
    fn from(shift: DisplayShift) -> Self {
        match shift {
            DisplayShift::On => EntryModeFlags::DISPLAY_SHIFT_ON,
            DisplayShift::Off => EntryModeFlags::DISPLAY_SHIFT_OFF,
        }
    }
}

/// A struct for creating display entry mode settings.
pub struct EntryModeBuilder {
    move_direction: MoveDirection,
    display_shift: DisplayShift,
}

impl EntryModeBuilder {
    /// Sets the direction the read/write cursor is moved when a character code is written to or
    /// read from the display.
    pub fn set_move_direction(&mut self, direction: MoveDirection) -> &mut Self {
        self.move_direction = direction;
        self
    }

    /// Sets the display shift, which will be performed on character write, either `On` or `Off`.
    ///
    /// If display shift is enabled, it will seem as if the cursor does not move but the display
    /// does.
    ///
    /// **Note:** The display does not shift when reading.
    pub fn set_display_shift(&mut self, shift: DisplayShift) -> &mut Self {
        self.display_shift = shift;
        self
    }

    pub(crate) fn build_command(&self) -> u8 {
        let mut cmd = EntryModeFlags::ENTRY_MODE;

        cmd |= EntryModeFlags::from(self.move_direction);
        cmd |= EntryModeFlags::from(self.display_shift);

        cmd.bits()
    }
}

impl Default for EntryModeBuilder {
    /// Make a new `EntryModeBuilder` with the default settings described below.
    ///
    /// The default settings are:
    ///
    ///  - **move direction:**
    ///     - `Increment`
    ///  - **display_shift:**
    ///     - `Off`
    fn default() -> Self {
        Self {
            move_direction: MoveDirection::Increment,
            display_shift: DisplayShift::Off,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    const ENTRY_MODE_FLAG: u8 = 0b0000_0100;
    const MOVE_DIRECTION_FLAG: u8 = 0b0000_0010;
    const DISPLAY_SHIFT_FLAG: u8 = 0b0000_0001;

    fn has_bit(value: u8, bitmask: u8) -> bool {
        value & bitmask == bitmask
    }

    #[test]
    fn entry_mode_flag() {
        let b = EntryModeBuilder::default();
        let cmd = b.build_command();

        assert!(has_bit(cmd, ENTRY_MODE_FLAG));
    }

    #[test]
    fn default_move_direction() {
        let b = EntryModeBuilder::default();
        let cmd = b.build_command();

        assert!(has_bit(cmd, MOVE_DIRECTION_FLAG));
    }

    #[test]
    fn set_move_direction() {
        let mut b = EntryModeBuilder::default();

        let cmd = b.build_command();
        assert!(has_bit(cmd, MOVE_DIRECTION_FLAG));

        b.set_move_direction(MoveDirection::Decrement);

        let cmd = b.build_command();
        assert_eq!(has_bit(cmd, MOVE_DIRECTION_FLAG), false);
    }

    #[test]
    fn default_display_shift() {
        let b = EntryModeBuilder::default();
        let cmd = b.build_command();

        assert_eq!(has_bit(cmd, DISPLAY_SHIFT_FLAG), false);
    }

    #[test]
    fn set_display_shift() {
        let mut b = EntryModeBuilder::default();

        let cmd = b.build_command();
        assert_eq!(has_bit(cmd, DISPLAY_SHIFT_FLAG), false);

        b.set_display_shift(DisplayShift::On);

        let cmd = b.build_command();
        assert!(has_bit(cmd, DISPLAY_SHIFT_FLAG));
    }
}