Add basic SPI example (#113)

rp2040-hal/examples/spi.rs

@@ -0,0 +1,74 @@
+//! Perform ]
+#![no_std]
+#![no_main]
+
+use cortex_m::prelude::{
+    _embedded_hal_blocking_spi_Transfer, _embedded_hal_blocking_spi_Write,
+    _embedded_hal_spi_FullDuplex,
+};
+use cortex_m_rt::entry;
+use embedded_hal::spi::MODE_0;
+use embedded_time::rate::Extensions;
+use hal::{gpio::FunctionSpi, pac, sio::Sio, spi::Spi};
+use panic_halt as _;
+use rp2040_hal as hal;
+
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
+
+const SYS_HZ: u32 = 125_000_000_u32;
+
+#[entry]
+fn main() -> ! {
+    let mut pac = pac::Peripherals::take().unwrap();
+
+    let sio = Sio::new(pac.SIO);
+    let pins = hal::gpio::Pins::new(
+        pac.IO_BANK0,
+        pac.PADS_BANK0,
+        sio.gpio_bank0,
+        &mut pac.RESETS,
+    );
+
+    // These are implicitly used by the spi driver if they are in the correct mode
+    let _spi_sclk = pins.gpio6.into_mode::<FunctionSpi>();
+    let _spi_mosi = pins.gpio7.into_mode::<FunctionSpi>();
+    let _spi_miso = pins.gpio4.into_mode::<FunctionSpi>();
+    let mut spi = Spi::<_, _, 8>::new(pac.SPI0).init(
+        &mut pac.RESETS,
+        SYS_HZ.Hz(),
+        16_000_000u32.Hz(),
+        &MODE_0,
+    );
+
+    // Write out 0, ignore return value
+    if let Ok(..) = spi.write(&[0]) {
+        // Handle success
+    };
+
+    // write 50, then check the return
+    let send_success = spi.send(50);
+    match send_success {
+        Ok(_) => {
+            // We succeeded, check the read value
+            if spi.read().is_ok() {
+                // Output our read value
+            };
+        }
+        Err(_) => todo!(),
+    }
+
+    // Do a read+write at the same time.
+    // Data in read_write_cache will be replaced with the read data
+    let mut read_write_cache: [u8; 4] = [1, 2, 3, 4];
+    let transfer_success = spi.transfer(&mut read_write_cache);
+    #[allow(clippy::single_match)]
+    match transfer_success {
+        Ok(_) => {}  // Handle success
+        Err(_) => {} // handle errors
+    };
+
+    #[allow(clippy::empty_loop)]
+    loop {}
+}