fw-rust: Create a print u8 function for setup

Create `print_u8()` helper function to print `u8` primitives to
lcd. Refactor contrast and backlight variables to also keep them in a
global `AtomicU8`.

firmware/rust/src/lcd.rs

@@ -5,6 +5,7 @@ use atmega_hal::{
     Spi,
 };
 use avr_device::interrupt;
+use core::convert::TryInto;
 use embedded_hal::{blocking::delay::DelayMs, spi::FullDuplex};
 use nb::block;
 
@@ -161,6 +162,39 @@ impl Lcd {
         }
     }
 
+    pub fn print_u8(&mut self, segment: u8, page: u8, digits: u8, data: u8) {
+        assert!(digits <= 3);
+        let mut delay = Delay::<MHz8>::new();
+
+        let mut array = [0usize; 3];
+        for (i, item) in array.iter_mut().enumerate() {
+            *item = ((data / 10_u8.pow(i.try_into().unwrap())) % 10).into();
+        }
+        array.reverse();
+
+        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 j in 3 - digits..3 {
+                for segment in SYMBOL_TABLE[array[j as usize]][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 draw(&mut self, screen: &Screens) {
         interrupt::free(|_cs| {
             self.clear();