Merge pull request #111 from flipperzero-rs/i2c

flipperzero: I2C interface

CHANGELOG.md

@@ -7,6 +7,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## Unreleased
 
+### Added
+
+- `flipperzero::gpio::i2c`, providing a Rust interface to the external 3.3V I2C
+  bus over GPIO pins C0 and C1, as well as the internal (power) I2C bus.
+
+### Changed
+
 - Migrated to SDK 39.1 (firmware 0.92.2).
 
 ## [0.11.0]

crates/flipperzero/examples/i2c-ds3231.rs

@@ -0,0 +1,81 @@
+//! Example of communicating with a [DS3231] Real-Time Clock.
+//!
+//! [DS3231]: https://www.analog.com/media/en/technical-documentation/data-sheets/DS3231.pdf
+
+#![no_main]
+#![no_std]
+
+// Required for panic handler
+extern crate flipperzero_rt;
+
+// Required for allocator
+#[cfg(feature = "alloc")]
+extern crate flipperzero_alloc;
+
+use flipperzero::{error, furi::time::Duration, gpio::i2c, println};
+use flipperzero_rt::{entry, manifest};
+use ufmt::derive::uDebug;
+
+manifest!(name = "I2C DS3231 Example");
+entry!(main);
+
+#[derive(Debug, uDebug)]
+enum Hour {
+    F12 { hour: u8, pm: bool },
+    F24(u8),
+}
+
+#[derive(Debug, uDebug)]
+struct RtcTime {
+    year: u8,
+    month: u8,
+    date: u8,
+    day: u8,
+    hour: Hour,
+    minutes: u8,
+    seconds: u8,
+}
+
+impl RtcTime {
+    fn parse(data: [u8; 7]) -> Self {
+        let unbcd = |b: u8| 10 * (b >> 4) + (b & 0x0F);
+
+        const FORMAT_12HR: u8 = 0b0100_0000;
+
+        Self {
+            year: unbcd(data[6]),
+            month: unbcd(data[5] & 0x1F),
+            date: unbcd(data[4] & 0x3F),
+            day: data[3] & 0x07,
+            hour: if data[2] & FORMAT_12HR != 0 {
+                Hour::F12 {
+                    hour: unbcd(data[2] & 0x1F),
+                    pm: data[2] & 0b0010_0000 != 0,
+                }
+            } else {
+                Hour::F24(unbcd(data[2] & 0x3F))
+            },
+            minutes: unbcd(data[1] & 0x7F),
+            seconds: unbcd(data[0] & 0x7F),
+        }
+    }
+}
+
+fn main(_args: *mut u8) -> i32 {
+    let mut bus = i2c::Bus::EXTERNAL.acquire();
+    let rtc = i2c::DeviceAddress::new(0x68);
+    let timeout = Duration::from_millis(50);
+
+    if bus.is_device_ready(rtc, timeout) {
+        let mut data = [0; 7];
+        if bus.read_exact(rtc, 0x00, &mut data, timeout).is_ok() {
+            println!("Time: {:?}", RtcTime::parse(data));
+        } else {
+            error!("Could not read from DS3231");
+        }
+    } else {
+        error!("DS3231 is not connected and ready");
+    }
+
+    0
+}