Added an spi example to test pull request #28 (#36)

Co-authored-by: Nando Bongers <[email protected]>

Author: NandoBongers

examples/spi-example.rs

@@ -0,0 +1,56 @@
+// This example is to test the SPI without any external devices.
+// It puts "Hello world!" on the mosi-line and logs whatever is received on the miso-line to the info level.
+// The idea is that you should connect miso and mosi, so you will also receive "Hello world!".
+
+#![no_main]
+#![no_std]
+
+use crate::hal::{
+    block, delay::DelayFromCountDownTimer, gpio::gpioa::PA5, gpio::gpioa::PA6, gpio::gpioa::PA7,
+    gpio::Alternate, gpio::AF5, prelude::*, rcc::Config, spi, stm32::Peripherals, timer::Timer,
+};
+
+use cortex_m_rt::entry;
+use log::info;
+use stm32g4xx_hal as hal;
+
+#[macro_use]
+mod utils;
+
+#[entry]
+fn main() -> ! {
+    utils::logger::init();
+
+    let dp = Peripherals::take().unwrap();
+    let rcc = dp.RCC.constrain();
+    let mut rcc = rcc.freeze(Config::hsi());
+    let timer2 = Timer::new(dp.TIM2, &rcc.clocks);
+    let mut delay_tim2 = DelayFromCountDownTimer::new(timer2.start_count_down(100.ms()));
+
+    let gpioa = dp.GPIOA.split(&mut rcc);
+    let sclk: PA5<Alternate<AF5>> = gpioa.pa5.into_alternate();
+    let miso: PA6<Alternate<AF5>> = gpioa.pa6.into_alternate();
+    let mosi: PA7<Alternate<AF5>> = gpioa.pa7.into_alternate();
+
+    let mut spi = dp
+        .SPI1
+        .spi((sclk, miso, mosi), spi::MODE_0, 400.khz(), &mut rcc);
+    let mut cs = gpioa.pa8.into_push_pull_output();
+    cs.set_high().unwrap();
+
+    // "Hello world!"
+    let message: [char; 12] = ['H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '!'];
+    let mut received_byte: u8;
+
+    loop {
+        for byte in message.iter() {
+            cs.set_low().unwrap();
+            spi.send(*byte as u8).unwrap();
+            received_byte = block!(spi.read()).unwrap();
+            cs.set_high().unwrap();
+
+            info!("{}", received_byte as char);
+        }
+        delay_tim2.delay_ms(1000_u16);
+    }
+}