My solution

#![no_main] #![no_std] use core::str; use cortex_m_rt::entry; use rtt_target::rtt_init_print; use panic_rtt_target as _; #[cfg(feature = "v1")] use microbit::{ hal::twi, pac::twi0::frequency::FREQUENCY_A, hal::uart, hal::uart::{Baudrate, Parity}, }; #[cfg(feature = "v2")] use microbit::{ hal::twim, pac::twim0::frequency::FREQUENCY_A, hal::uarte, hal::uarte::{Baudrate, Parity}, }; use microbit::hal::prelude::*; use lsm303agr::{AccelOutputDataRate, MagOutputDataRate, Lsm303agr}; use heapless::Vec; use nb::block; use core::fmt::Write; #[cfg(feature = "v2")] mod serial_setup; #[cfg(feature = "v2")] use serial_setup::UartePort; #[entry] fn main() -> ! { rtt_init_print!(); let board = microbit::Board::take().unwrap(); #[cfg(feature = "v1")] let mut serial = { uart::Uart::new( board.UART0, board.uart.into(), Parity::EXCLUDED, Baudrate::BAUD115200, ) }; #[cfg(feature = "v2")] let mut serial = { let serial = uarte::Uarte::new( board.UARTE0, board.uart.into(), Parity::EXCLUDED, Baudrate::BAUD115200, ); UartePort::new(serial) }; #[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); sensor.init().unwrap(); sensor.set_accel_odr(AccelOutputDataRate::Hz50).unwrap(); sensor.set_mag_odr(MagOutputDataRate::Hz50).unwrap(); let mut sensor = sensor.into_mag_continuous().ok().unwrap(); loop { let mut buffer: Vec<u8, 32> = Vec::new(); loop { let byte = block!(serial.read()).unwrap(); if byte == 13 { break; } if buffer.push(byte).is_err() { write!(serial, "error: buffer full\r\n").unwrap(); break; } } if str::from_utf8(&buffer).unwrap().trim() == "accelerometer" { while !sensor.accel_status().unwrap().xyz_new_data { } let data = sensor.accel_data().unwrap(); write!(serial, "Accelerometer: x {} y {} z {}\r\n", data.x, data.y, data.z).unwrap(); } else if str::from_utf8(&buffer).unwrap().trim() == "magnetometer" { while !sensor.mag_status().unwrap().xyz_new_data { } let data = sensor.mag_data().unwrap(); write!(serial, "Magnetometer: x {} y {} z {}\r\n", data.x, data.y, data.z).unwrap(); } else { write!(serial, "error: command not detected\r\n").unwrap(); } } }