tymek.me
A custom OS for the xteink x4 ebook reader
1// button definitions and ADC resistance ladder decoding
2// two ADC ladders (Row1 GPIO1, Row2 GPIO2) plus power button (GPIO3)
3
4#[derive(Debug, Clone, Copy, PartialEq, Eq)]
5pub enum Button {
6 Right,
7 Left,
8 Confirm,
9 Back,
10 VolUp,
11 VolDown,
12 Power,
13}
14
15impl Button {
16 pub const fn name(self) -> &'static str {
17 match self {
18 Button::Right => "Right",
19 Button::Left => "Left",
20 Button::Confirm => "Confirm",
21 Button::Back => "Back",
22 Button::VolUp => "Vol Up",
23 Button::VolDown => "Vol Down",
24 Button::Power => "Power",
25 }
26 }
27}
28
29impl core::fmt::Display for Button {
30 fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
31 f.write_str(self.name())
32 }
33}
34
35pub const DEFAULT_TOLERANCE: u16 = 150;
36
37// (center_mv, tolerance_mv, button)
38pub const ROW1_THRESHOLDS: &[(u16, u16, Button)] = &[
39 (3, 50, Button::Right),
40 (1113, DEFAULT_TOLERANCE, Button::Left),
41 (1984, DEFAULT_TOLERANCE, Button::Confirm),
42 (2556, DEFAULT_TOLERANCE, Button::Back),
43];
44
45pub const ROW2_THRESHOLDS: &[(u16, u16, Button)] = &[
46 (3, 50, Button::VolDown),
47 (1659, DEFAULT_TOLERANCE, Button::VolUp),
48];
49
50impl Button {
51 /// Decode a button from an ADC millivolt reading using a resistance
52 /// ladder threshold table. Returns `None` if no threshold matches.
53 pub fn from_ladder(mv: u16, thresholds: &[(u16, u16, Button)]) -> Option<Button> {
54 for &(center, tolerance, button) in thresholds {
55 let low = center.saturating_sub(tolerance);
56 let high = center.saturating_add(tolerance);
57 if mv >= low && mv <= high {
58 return Some(button);
59 }
60 }
61 None
62 }
63}