Add magnetometer example

Uses LSM303AGR driver from eldruin mentioned here
#27 (comment)

This example works on the micro:bit V1.5 and V2. The micro:bit V1.3 uses
a different magnetometer.

Author: robyoung

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Add BLE Beacon demo.
 - Add a simple speaker demo for micro:bit V2.
 - Add Board struct following the pattern used in other nrf board support crates.
+- Add magnetometer example.
 
 ## [0.10.1] - 2021-05-25
 

examples/magnetometer/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+name = "magnetometer"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+cortex-m-rt = "0.6.12"
+panic-halt = "0.2.0"
+defmt-rtt = "0.2.0"
+defmt = "0.2.0"
+lsm303agr = "0.2.0"
+
+[dependencies.microbit]
+path = "../../microbit"
+optional = true
+
+[dependencies.microbit-v2]
+path = "../../microbit-v2"
+optional = true
+
+[features]
+v1 = ["microbit"]
+v2 = ["microbit-v2"]
+
+default = [
+  "defmt-default",
+]
+
+# do NOT modify these features
+defmt-default = []
+defmt-trace = []
+defmt-debug = []
+defmt-info = []
+defmt-warn = []
+defmt-error = []

examples/magnetometer/src/main.rs

@@ -0,0 +1,80 @@
+#![no_std]
+#![no_main]
+
+use defmt_rtt as _;
+use panic_halt as _;
+
+use cortex_m_rt::entry;
+
+use microbit::hal::{prelude::*, Timer};
+
+#[cfg(feature = "v1")]
+use microbit::{
+    hal::twi,
+    pac::{twi0::frequency::FREQUENCY_A, TWI0},
+};
+#[cfg(feature = "v2")]
+use microbit::{
+    hal::twim,
+    pac::{twim0::frequency::FREQUENCY_A, TWIM0},
+};
+
+use lsm303agr::{
+    interface::I2cInterface, mode::MagOneShot, AccelMode, AccelOutputDataRate, Lsm303agr,
+};
+
+#[entry]
+fn main() -> ! {
+    let board = microbit::Board::take().unwrap();
+    let mut timer = Timer::new(board.TIMER0);
+
+    #[cfg(feature = "v1")]
+    let i2c = { twi::Twi::new(board.TWI0, board.i2c.into(), FREQUENCY_A::K100) };
+
+    #[cfg(feature = "v2")]
+    let i2c = { twim::Twim::new(board.TWIM0, board.i2c_internal.into(), FREQUENCY_A::K100) };
+
+    let mut sensor = Lsm303agr::new_with_i2c(i2c);
+    match sensor.accelerometer_id() {
+        Ok(0x33u8) => {}
+        _ => defmt::panic!("accelerometer not found"),
+    }
+    sensor.init().unwrap();
+    sensor.set_accel_odr(AccelOutputDataRate::Hz50).unwrap();
+
+    defmt::info!("normal mode");
+    sensor.set_accel_mode(AccelMode::Normal).unwrap();
+    timer.delay_ms(1000_u32);
+    get_data(&mut sensor);
+
+    defmt::info!("low power mode");
+    sensor.set_accel_mode(AccelMode::LowPower).unwrap();
+    timer.delay_ms(1000_u32);
+    get_data(&mut sensor);
+
+    defmt::info!("high resolution mode");
+    sensor.set_accel_mode(AccelMode::HighResolution).unwrap();
+    timer.delay_ms(1000_u32);
+    get_data(&mut sensor);
+
+    loop {
+        timer.delay_ms(100_u32);
+        get_data(&mut sensor);
+    }
+}
+
+#[cfg(feature = "v1")]
+type Sensor = Lsm303agr<I2cInterface<twi::Twi<TWI0>>, MagOneShot>;
+
+#[cfg(feature = "v2")]
+type Sensor = Lsm303agr<I2cInterface<twim::Twim<TWIM0>>, MagOneShot>;
+
+fn get_data(sensor: &mut Sensor) {
+    loop {
+        if sensor.accel_status().unwrap().xyz_new_data {
+            let data = sensor.accel_data().unwrap();
+            defmt::info!("x {} y {} z {}", data.x, data.y, data.z);
+            return;
+        }
+    }
+}

microbit-common/src/v1/board.rs

@@ -1,6 +1,9 @@
-use super::gpio::{DisplayPins, BTN_A, BTN_B};
+use super::gpio::{DisplayPins, BTN_A, BTN_B, SCL, SDA};
 use crate::{
-    hal::gpio::{p0, Disconnected, Level},
+    hal::{
+        gpio::{p0, Disconnected, Level},
+        twi,
+    },
     pac,
 };
 
@@ -16,6 +19,9 @@ pub struct Board {
     /// buttons
     pub buttons: Buttons,
 
+    /// I2C shared internal and external bus pins
+    pub i2c: I2CPins,
+
     /// Core peripheral: Cache and branch predictor maintenance operations
     pub CBP: pac::CBP,
 
@@ -75,6 +81,9 @@ pub struct Board {
 
     /// nRF51 peripheral: TIMER2
     pub TIMER2: pac::TIMER2,
+
+    /// nRF51 peripheral: TWI0
+    pub TWI0: pac::TWI0,
 }
 
 impl Board {
@@ -93,7 +102,6 @@ impl Board {
         let p0parts = p0::Parts::new(p.GPIO);
         Self {
             pins: Pins {
-                p0_00: p0parts.p0_00,
                 p0_01: p0parts.p0_01,
                 p0_02: p0parts.p0_02,
                 p0_03: p0parts.p0_03,
@@ -109,7 +117,6 @@ impl Board {
                 p0_27: p0parts.p0_27,
                 p0_28: p0parts.p0_28,
                 p0_29: p0parts.p0_29,
-                p0_30: p0parts.p0_30,
             },
             display_pins: DisplayPins {
                 row1: p0parts.p0_13.into_push_pull_output(Level::High),
@@ -129,6 +136,10 @@ impl Board {
                 button_a: p0parts.p0_17.into_floating_input(),
                 button_b: p0parts.p0_26.into_floating_input(),
             },
+            i2c: I2CPins {
+                scl: p0parts.p0_00.into_floating_input(),
+                sda: p0parts.p0_30.into_floating_input(),
+            },
 
             // Core peripherals
             CBP: cp.CBP,
@@ -153,14 +164,15 @@ impl Board {
             TIMER0: p.TIMER0,
             TIMER1: p.TIMER1,
             TIMER2: p.TIMER2,
+            TWI0: p.TWI0,
         }
     }
 }
 
 /// Unused GPIO pins
 #[allow(missing_docs)]
 pub struct Pins {
-    pub p0_00: p0::P0_00<Disconnected>,
+    // pub p0_00: p0::P0_00<Disconnected>, // SCL
     pub p0_01: p0::P0_01<Disconnected>,
     pub p0_02: p0::P0_02<Disconnected>,
     pub p0_03: p0::P0_03<Disconnected>,
@@ -190,7 +202,7 @@ pub struct Pins {
     pub p0_27: p0::P0_27<Disconnected>,
     pub p0_28: p0::P0_28<Disconnected>,
     pub p0_29: p0::P0_29<Disconnected>,
-    pub p0_30: p0::P0_30<Disconnected>,
+    // pub p0_30: p0::P0_30<Disconnected>, // SDA
 }
 
 /// Board buttons
@@ -200,3 +212,18 @@ pub struct Buttons {
     /// Right hand side button
     pub button_b: BTN_B,
 }
+
+/// I2C shared internal and external bus pins
+pub struct I2CPins {
+    scl: SCL,
+    sda: SDA,
+}
+
+impl Into<twi::Pins> for I2CPins {
+    fn into(self) -> twi::Pins {
+        twi::Pins {
+            scl: self.scl.degrade(),
+            sda: self.sda.degrade(),
+        }
+    }
+}

microbit-common/src/v1/gpio.rs

@@ -127,7 +127,7 @@ pub type MOSI<MODE> = p0::P0_21<MODE>;
 pub type MISO<MODE> = p0::P0_22<MODE>;
 pub type SCK<MODE> = p0::P0_23<MODE>;
 
-/* i2c */
+/* i2c - shared external and internal */
 pub type SCL = p0::P0_00<Input<Floating>>;
 pub type SDA = p0::P0_30<Input<Floating>>;