fw-rust: Break everything down in multiple files

To reduce length of `main.rs` and therefor improve readability create
source files for:

- Assets (`assets.rs`): Contains all graphical assets such as the
  splash screen assets, symbols and the symbol table.
- LCD (`lcd.rs`): Contains all lower level things regarding the LCD
  such as the `Lcd` struct and its implementations.
- Screen (`screen/mod.rs`):
    - Splash (`screen/splash.rs`)
    - Home (`screen/home.rs`)
    - Setup (`screen/setup.rs`)

In the future it would probably make sense to move the LCD module into
the screen module.

firmware/rust/src/lcd.rs

@@ -0,0 +1,181 @@
+use atmega_hal::{
+    clock::MHz8,
+    delay::Delay,
+    port::{mode::Output, Pin, PB0, PB1},
+    Spi,
+};
+use avr_device::interrupt;
+use embedded_hal::{blocking::delay::DelayMs, spi::FullDuplex};
+use nb::block;
+
+use crate::{
+    assets::SYMBOL_TABLE,
+    screen::{Screen, Screens},
+};
+
+// TODO: Make `cd` and `rst` pins generic pins
+pub struct Lcd {
+    pub spi: Spi,
+    pub cd: Pin<Output, PB0>,
+    rst: Pin<Output, PB1>,
+}
+
+impl Lcd {
+    pub fn new(spi: Spi, cd: Pin<Output, PB0>, rst: Pin<Output, PB1>) -> Self {
+        Self { spi, cd, rst }
+    }
+
+    pub fn init(&mut self, contrast: u8) {
+        let mut delay = Delay::<MHz8>::new();
+
+        // TODO: Test if delay is really needed
+        delay.delay_ms(1_u8);
+        self.rst.set_high();
+        // TODO: Try to reduce delay to a minimum
+        delay.delay_ms(1_u8);
+
+        block!(self.spi.send(0x40)).unwrap(); // (6)  Set Scroll Line: Display start line 0
+        block!(self.spi.send(0xA1)).unwrap(); // (13) Set SEG direction: SEG reverse
+        block!(self.spi.send(0xC0)).unwrap(); // (14) Set COM direction: Normal COM0 - COM63
+                                              // block!(spi.send(0xA4)).unwrap(); // (10) Set All Pixel On: Disable -> Set All Pixel to ON */
+        block!(self.spi.send(0xA6)).unwrap(); // (11) Set Inverse Display: Display inverse off
+        block!(self.spi.send(0xA2)).unwrap(); // (17) Set LCD Bias Ratio: Set Bias 1/9 (Duty 1/65)
+        block!(self.spi.send(0x2F)).unwrap(); // (5)  Set Power Control: Booster, Regulator and Follower on
+        block!(self.spi.send(0x27)).unwrap(); // (8)  Set VLCD Resistor Ratio: Set Contrast
+                                              // block!(spi.send(0xEE)).unwrap(); // (18) Reset Cursor Update Mode
+        block!(self.spi.send(0x81)).unwrap(); // (9)  Set Electronic Volume: Set Contrast
+        block!(self.spi.send(contrast)).unwrap(); // (9)  Set Electronic Volume: Set Contrast
+                                                  // block!(spi.send(0xFA)).unwrap(); // (25) Set Adv. Program Control 0: Set Temperature compensation curve to -0.11%/°C
+                                                  // block!(spi.send(0x90)).unwrap(); // (25) Set Adv. Program Control 0: Set Temperature compensation curve to -0.11%/°C
+        block!(self.spi.send(0xAF)).unwrap(); // (12) Set Display Enable: Display on
+
+        // TODO: This delay fixes issues, try find a better solution
+        delay.delay_ms(1_u8);
+    }
+
+    pub fn move_cursor(&mut self, segment: u8, page: u8) {
+        assert!(segment < 102);
+        assert!(page < 8);
+
+        block!(self.spi.send(0x0F & segment)).unwrap();
+        block!(self.spi.send(0x10 + (segment >> 4))).unwrap();
+        block!(self.spi.send(0xB0 + page)).unwrap();
+    }
+
+    fn clear(&mut self) {
+        let mut delay = Delay::<MHz8>::new();
+
+        for page in 0..8 {
+            self.move_cursor(0, page as u8);
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_high();
+
+            for _ in 0..102 {
+                block!(self.spi.send(0x00)).unwrap();
+            }
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_low();
+        }
+    }
+
+    fn fill(&mut self, segment: u8, page: u8, width: u8, data: u8) {
+        assert!(segment + width <= 102);
+        let mut delay = Delay::<MHz8>::new();
+
+        self.move_cursor(segment, page);
+
+        // TODO: This delay fixes issues, try find a better solution
+        delay.delay_ms(1_u8);
+        self.cd.set_high();
+
+        for _ in 0..width {
+            block!(self.spi.send(data)).unwrap();
+        }
+
+        // TODO: This delay fixes issues, try find a better solution
+        delay.delay_ms(1_u8);
+        self.cd.set_low();
+    }
+
+    pub fn fill_area(&mut self, segment: u8, page: u8, width: u8, height: u8, data: u8) {
+        assert!(page + height <= 8);
+
+        for i in 0..height {
+            self.fill(segment, page + i, width, data);
+        }
+    }
+
+    pub fn print(&mut self, segment: u8, page: u8, string: &str) {
+        let mut delay = Delay::<MHz8>::new();
+
+        for i in 0..2 {
+            self.move_cursor(segment, page + i);
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_high();
+
+            block!(self.spi.send(0x00)).unwrap();
+            block!(self.spi.send(0x00)).unwrap();
+            for c in string.chars() {
+                for segment in SYMBOL_TABLE[c as usize - 48][i as usize] {
+                    block!(self.spi.send(*segment)).unwrap();
+                }
+                block!(self.spi.send(0x00)).unwrap();
+            }
+            block!(self.spi.send(0x00)).unwrap();
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_low();
+        }
+    }
+
+    pub fn print_inverted(&mut self, segment: u8, page: u8, string: &str) {
+        let mut delay = Delay::<MHz8>::new();
+
+        for i in 0..2 {
+            self.move_cursor(segment, page + i);
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_high();
+
+            block!(self.spi.send(0xFF)).unwrap();
+            block!(self.spi.send(0xFF)).unwrap();
+            for c in string.chars() {
+                for segment in SYMBOL_TABLE[c as usize - 48][i as usize] {
+                    block!(self.spi.send(!*segment)).unwrap();
+                }
+                block!(self.spi.send(0xFF)).unwrap();
+            }
+            block!(self.spi.send(0xFF)).unwrap();
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            self.cd.set_low();
+        }
+    }
+
+    pub fn draw(&mut self, screen: &Screens) {
+        interrupt::free(|_cs| {
+            self.clear();
+
+            match screen {
+                Screens::Splash(splash) => {
+                    splash.draw(self);
+                }
+                Screens::Home(home) => {
+                    home.draw(self);
+                }
+                Screens::Setup(setup) => {
+                    setup.draw(self);
+                }
+            }
+        });
+    }
+}