Add trivial SPI example

Author: jannic

examples/spi.rs

@@ -0,0 +1,30 @@
+use embedded_hal::spi::{SpiDevice, Operation};
+use linux_embedded_hal::SpidevDevice;
+
+struct Driver<SPI> {
+    spi: SPI,
+}
+
+impl<SPI> Driver<SPI>
+where
+    SPI: SpiDevice,
+{
+    pub fn new(spi: SPI) -> Self {
+        Driver { spi }
+    }
+
+    fn read_write(&mut self) -> Result<u8, SPI::Error> {
+        let mut buffer = [ 1, 2, 3 ];
+        let mut ops = [
+            Operation::TransferInPlace(&mut buffer)
+        ];
+        self.spi.transaction(&mut ops).and(Ok(buffer[0]))
+    }
+}
+
+fn main() {
+    let dev = SpidevDevice::open("/dev/spidev0.0").unwrap();
+    let mut driver = Driver::new(dev);
+    let value = driver.read_write().unwrap();
+    println!("Read value: {}", value);
+}