examples: Add spi-eh1-loopback example

Add embedded-hal-1 traits usage example for SpiBus.

Author: plaes

examples/spi-eh1-loopback.rs

@@ -0,0 +1,92 @@
+//! This is a loopback example for embedded-hal-1 traits:
+//! * SpiBus
+//! * SpiDevice (TODO)
+//! Pin setup:
+//! * D1 <-> D2 (connect SDO with SDI)
+//! Leave other pins unconnected.
+use ftdi_embedded_hal as hal;
+use std::thread::sleep;
+use std::time::Duration;
+
+fn main() {
+    cfg_if::cfg_if! {
+        if #[cfg(feature = "ftdi")] {
+            let device = ftdi::find_by_vid_pid(0x0403, 0x6014)
+                .interface(ftdi::Interface::A)
+                .open()
+                .unwrap();
+        } else if #[cfg(feature = "libftd2xx")] {
+            let device = libftd2xx::Ft232h::with_description("Single RS232-HS").unwrap();
+        } else {
+            compile_error!("one of features 'ftdi' and 'libftd2xx' shall be enabled");
+        }
+    }
+
+    let hal = hal::FtHal::init_freq(device, 1_000_000).unwrap();
+    let mut spi = hal.spi().unwrap();
+
+    let delay = Duration::from_millis(250);
+
+    {
+        use hal::eh1::spi::SpiBus;
+
+        println!("=== SpiBus example with embedded-hal-1 traits ===");
+
+        // --- Symmetric transfer (Read as much as we write) ---
+        print!("Starting symmetric transfer...");
+        let write = [0xde, 0xad, 0xbe, 0xef];
+        let mut read: [u8; 4] = [0x00u8; 4];
+        SpiBus::transfer(&mut spi, &mut read[..], &write[..]).expect("Symmetric transfer failed");
+        assert_eq!(write, read);
+        println!(" SUCCESS");
+
+        // XXX: After we do an asymmetric transfer, we still have two leftover
+        // bytes are still in the read buffer, which breaks tests afterwards.
+        // Spi::flush(&mut spi) doesn't help either
+
+        /*
+        // --- Asymmetric transfer (Read more than we write) ---
+        print!("Starting asymetric transfer (read > write)...");
+        let mut read: [u8; 4] = [0x00; 4];
+
+        SpiBus::transfer(&mut spi, &mut read[0..2], &write[..])
+            .expect("Asymmetric transfer failed");
+        assert_eq!(write[0], read[0]);
+        assert_eq!(read[2], 0x00u8);
+        println!(" SUCCESS");
+        sleep(delay);
+        */
+
+        // --- Symmetric transfer with huge buffer ---
+        // Only your RAM is the limit!
+        print!("Starting huge transfer...");
+        let mut write = [0x55u8; 4096];
+        for byte in 0..write.len() {
+            write[byte] = byte as u8;
+        }
+        let mut read = [0x00u8; 4096];
+        sleep(delay);
+
+        SpiBus::transfer(&mut spi, &mut read[..], &write[..]).expect("Huge transfer failed");
+        assert_eq!(write, read);
+        println!(" SUCCESS");
+        sleep(delay);
+
+        // --- Symmetric transfer with huge buffer in-place (No additional allocation
+        // needed) ---
+        print!("Starting huge transfer (in-place)...");
+        let mut write = [0x55u8; 4096];
+        for byte in 0..write.len() {
+            write[byte] = byte as u8;
+        }
+
+        SpiBus::transfer_in_place(&mut spi, &mut write[..]).expect("Huge transfer failed");
+        for byte in 0..write.len() {
+            assert_eq!(write[byte], byte as u8);
+        }
+        println!(" SUCCESS");
+        sleep(delay);
+    }
+
+    // TODO: eh1 SpiDevice
+}