fw-rust: Prepare to implement Si5351 commands

Show settings of Si5351 channels on home screen. Initialize I2c and
Si5351.

firmware/rust/src/main.rs

@@ -28,6 +28,9 @@ mod screen;
 use rotary::{Direction, Rotary};
 use screen::{Screen, Screens};
 
+pub type DefaultClock = MHz8;
+pub type I2c = atmega_hal::i2c::I2c<DefaultClock>;
+
 #[used]
 #[link_section = ".eeprom"]
 static BACKLIGHT: u8 = 0;
@@ -54,7 +57,6 @@ struct ClockGenerator {
 
 impl ClockGenerator {
     fn new() -> Self {
-        // Get peripherals, pins and eeprom
         let dp = Peripherals::take().unwrap();
         let pins = pins!(dp);
 
@@ -82,6 +84,12 @@ impl ClockGenerator {
                 pins.pd5.into_output(),
                 pins.pb0.into_output(),
                 pins.pb1.into_output(),
+                I2c::new(
+                    dp.TWI,
+                    pins.pc4.into_pull_up_input(),
+                    pins.pc5.into_pull_up_input(),
+                    50000,
+                ),
             ),
             tc1: dp.TC1,
             exint: dp.EXINT,