Add I2C scanner example

Inspired from https://github.com/stm32-rs/stm32f3xx-hal/blob/master/examples/i2c_scanner.rs

Signed-off-by: Moritz Scheuren <[email protected]>

Author: systec-ms

examples/i2c_scanner.rs

@@ -0,0 +1,61 @@
+//! Example of using I2C.
+//! Scans available I2C devices on bus and print the result.
+
+#![no_std]
+#![no_main]
+
+use core::ops::Range;
+
+use panic_semihosting as _;
+
+use cortex_m_rt::entry;
+use cortex_m_semihosting::{hprint, hprintln};
+
+use stm32f7xx_hal::{self as hal, gpio::GpioExt, pac, prelude::*};
+
+const VALID_ADDR_RANGE: Range<u8> = 0x08..0x78;
+
+#[entry]
+fn main() -> ! {
+    let dp = pac::Peripherals::take().unwrap();
+
+    let mut rcc = dp.RCC.constrain();
+    let clocks = rcc.cfgr.freeze();
+
+    let gpiob = dp.GPIOB.split();
+
+    // Configure I2C1
+    let scl = gpiob.pb8.into_alternate_open_drain::<4>();
+    let sda = gpiob.pb7.into_alternate_open_drain::<4>();
+    let mut i2c = hal::i2c::BlockingI2c::i2c1(
+        dp.I2C1,
+        (scl, sda),
+        hal::i2c::Mode::fast(100_000.Hz()),
+        clocks,
+        &mut rcc.apb1,
+        50_000,
+    );
+
+    hprintln!("Start i2c scanning...").expect("Error using hprintln.");
+    hprintln!().unwrap();
+
+    for addr in 0x00_u8..0x80 {
+        // Write the empty array and check the slave response.
+        let byte: [u8; 1] = [0; 1];
+        if VALID_ADDR_RANGE.contains(&addr) && i2c.write(addr, &byte).is_ok() {
+            hprint!("{:02x}", addr).unwrap();
+        } else {
+            hprint!("..").unwrap();
+        }
+        if addr % 0x10 == 0x0F {
+            hprintln!().unwrap();
+        } else {
+            hprint!(" ").unwrap();
+        }
+    }
+
+    hprintln!().unwrap();
+    hprintln!("Done!").unwrap();
+
+    loop {}
+}