fw-rust: Create a SPI interface for the display

In order to, later on, send data to the display create a SPI
interface.

firmware/rust/src/main.rs

@@ -1,8 +1,13 @@
 #![no_std]
 #![no_main]
 
-use atmega_hal::{pins, Peripherals};
+use atmega_hal::{
+    pins,
+    spi::{DataOrder, SerialClockRate, Settings, Spi},
+    Peripherals,
+};
 use avr_device::interrupt;
+use embedded_hal::spi::{Mode, Phase, Polarity};
 use panic_halt as _;
 
 #[atmega_hal::entry]
@@ -31,6 +36,23 @@ fn main() -> ! {
     tc0.ocr0b.write(|w| unsafe { w.bits(0) });
     pins.pd5.into_output();
 
+    // Init SPI
+    let (_, _) = Spi::new(
+        dp.SPI,
+        pins.pb5.into_output(),
+        pins.pb3.into_output(),
+        pins.pb4.into_pull_up_input(),
+        pins.pb2.into_output(),
+        Settings {
+            data_order: DataOrder::MostSignificantFirst,
+            clock: SerialClockRate::OscfOver2,
+            mode: Mode {
+                polarity: Polarity::IdleLow,
+                phase: Phase::CaptureOnFirstTransition,
+            },
+        },
+    );
+
     // Enable interrupts
     unsafe { interrupt::enable() };