Merge pull request #758 from stm32-rs/i2c-scanner

I2c scanner

Author: burrbull

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+ - `i2c_scanner` example
+
 ### Changed
 
  - Use `stm32f4-staging` until `stm32f4` is released [#706]

examples/i2c_scanner.rs

@@ -0,0 +1,68 @@
+//! Example of using I2C.
+//! Scans available I2C devices on bus and print the result.
+
+#![no_std]
+#![no_main]
+
+use core::ops::Range;
+
+use rtt_target::{rprint, rprintln, rtt_init_print};
+
+use cortex_m_rt::entry;
+
+use stm32f4xx_hal::{self as hal, gpio::GpioExt, i2c::I2c, pac, prelude::*};
+
+const VALID_ADDR_RANGE: Range<u8> = 0x08..0x78;
+
+#[entry]
+fn main() -> ! {
+    rtt_init_print!();
+    let dp = pac::Peripherals::take().unwrap();
+
+    let rcc = dp.RCC.constrain();
+    let clocks = rcc.cfgr.freeze();
+
+    let gpiob = dp.GPIOB.split();
+
+    // Configure I2C1
+    let scl = gpiob.pb8;
+    let sda = gpiob.pb7;
+    let mut i2c = I2c::new(
+        dp.I2C1,
+        (scl, sda),
+        hal::i2c::Mode::standard(100.kHz()),
+        &clocks,
+    );
+
+    rprintln!("Start i2c scanning...");
+    rprintln!();
+
+    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() {
+            rprint!("{:02x}", addr);
+        } else {
+            rprint!("..");
+        }
+        if addr % 0x10 == 0x0F {
+            rprintln!();
+        } else {
+            rprint!(" ");
+        }
+    }
+
+    rprintln!();
+    rprintln!("Done!");
+
+    #[allow(clippy::empty_loop)]
+    loop {}
+}
+
+use core::panic::PanicInfo;
+#[inline(never)]
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
+    rprintln!("{}", info);
+    loop {} // You might need a compiler fence in here.
+}