我正在尝试在 BBC:Microbit 上用 Rust 编写一些程序。这个关于 rust 的微控制器的书还没有完成，所以我遗漏了一些观点。
实际上，我对 I2C 总线有一些问题。有 Rust crate microbit https://github.com/therealprof/microbit允许使用外设，它有一些漂亮的例子。但是，我不确定它们是否都在工作。
当我尝试运行名为i2c_direct_printmagserial我猜应该打印一些磁力计读数的示例时，我只收到以下消息：
Welcome to the magnetometer reader!
这就是代码的样子
#![no_std]
use panic_halt as _;
use microbit::hal::nrf51::*;
use microbit::hal::nrf51::{interrupt, UART0};
use microbit::NVIC;
use cortex_m::interrupt::Mutex;
use core::cell::RefCell;
use core::fmt::Write;
use cortex_m_rt::entry;
static RTC: Mutex<RefCell<Option<RTC0>>> = Mutex::new(RefCell::new(None));
static UART: Mutex<RefCell<Option<UART0>>> = Mutex::new(RefCell::new(None));
static TWI: Mutex<RefCell<Option<TWI1>>> = Mutex::new(RefCell::new(None));
#[entry]
fn main() -> ! {
if let Some(p) = microbit::Peripherals::take() {
p.CLOCK.tasks_lfclkstart.write(|w| unsafe { w.bits(1) });
while p.CLOCK.events_lfclkstarted.read().bits() == 0 {}
/* And then set it back to 0 again, just because ?!? */
p.CLOCK.events_lfclkstarted.write(|w| unsafe { w.bits(0) });
p.GPIO.pin_cnf[24].write(|w| w.pull().pullup().dir().output());
p.GPIO.pin_cnf[25].write(|w| w.pull().disabled().dir().input());
p.UART0.pseltxd.write(|w| unsafe { w.bits(24) });
p.UART0.pselrxd.write(|w| unsafe { w.bits(25) });
p.UART0.baudrate.write(|w| w.baudrate().baud115200());
p.UART0.enable.write(|w| w.enable().enabled());
let _ = write!(
UART0Buffer(&p.UART0),
"\n\rWelcome to the magnetometer reader!\n\r"
);
p.RTC0.prescaler.write(|w| unsafe { w.bits(4095) });
p.RTC0.evtenset.write(|w| w.tick().set_bit());
p.RTC0.intenset.write(|w| w.tick().set_bit());
p.RTC0.tasks_start.write(|w| unsafe { w.bits(1) });
/* Prepare PIN0 and PIN30 for I2C SDA and SCL */
p.GPIO.pin_cnf[0].write(|w| w.pull().disabled().dir().input().drive().s0d1());
p.GPIO.pin_cnf[30].write(|w| w.pull().disabled().dir().input().drive().s0d1());
{
let twi = &p.TWI1;
/* Set pins 0 and 30 for I2C SDA and SCL */
twi.pselscl.write(|w| unsafe { w.bits(0) });
twi.pselsda.write(|w| unsafe { w.bits(30) });
/* Enable I2C */
twi.enable.write(|w| w.enable().enabled());
/* Configure magnetometer for automatic updates */
twi.address.write(|w| unsafe { w.address().bits(0x0E) });
twi.tasks_starttx.write(|w| unsafe { w.bits(1) });
twi.txd.write(|w| unsafe { w.bits(0x10) });
while twi.events_txdsent.read().bits() == 0 {}
twi.events_txdsent.write(|w| unsafe { w.bits(0) });
twi.txd.write(|w| unsafe { w.bits(0x1) });
while twi.events_txdsent.read().bits() == 0 {}
twi.events_txdsent.write(|w| unsafe { w.bits(0) });
twi.tasks_stop.write(|w| unsafe { w.bits(1) });
twi.address.write(|w| unsafe { w.address().bits(0x0E) });
twi.tasks_starttx.write(|w| unsafe { w.bits(1) });
twi.txd.write(|w| unsafe { w.bits(0x11) });
while twi.events_txdsent.read().bits() == 0 {}
twi.events_txdsent.write(|w| unsafe { w.bits(127) });
twi.txd.write(|w| unsafe { w.bits(0x1) });
while twi.events_txdsent.read().bits() == 0 {}
twi.events_txdsent.write(|w| unsafe { w.bits(0) });
twi.tasks_stop.write(|w| unsafe { w.bits(1) });
}
cortex_m::interrupt::free(move |cs| {
*RTC.borrow(cs).borrow_mut() = Some(p.RTC0);
*UART.borrow(cs).borrow_mut() = Some(p.UART0);
*TWI.borrow(cs).borrow_mut() = Some(p.TWI1);
});
unsafe {
NVIC::unmask(microbit::Interrupt::RTC0);
}
microbit::NVIC::unpend(microbit::Interrupt::RTC0);
}
loop {
continue;
}
}
// Define an interrupt handler, i.e. function to call when exception occurs. Here if our timer
// trips, we'll read data from the accelerometer
#[interrupt]
fn RTC0() {
/* Enter critical section */
cortex_m::interrupt::free(|cs| {
if let (Some(rtc), Some(twi)) = (
RTC.borrow(cs).borrow().as_ref(),
TWI.borrow(cs).borrow().as_ref(),
) {
let mut data: [u8; 6] = [0; 6];
/* Request data */
twi.address.write(|w| unsafe { w.address().bits(0x0E) });
twi.tasks_starttx.write(|w| unsafe { w.bits(1) });
twi.txd.write(|w| unsafe { w.bits(0x1) });
while twi.events_txdsent.read().bits() == 0 {}
twi.events_txdsent.write(|w| unsafe { w.bits(0) });
/* Turn around to read data */
twi.shorts.write(|w| w.bb_suspend().enabled());
twi.tasks_startrx.write(|w| unsafe { w.bits(1) });
/* Get 5 values */
for d in &mut data {
while twi.events_rxdready.read().bits() == 0 {}
*d = twi.rxd.read().bits() as u8;
twi.events_rxdready.write(|w| unsafe { w.bits(0) });
twi.tasks_resume.write(|w| unsafe { w.bits(1) });
}
/* Get the last value */
twi.shorts.write(|w| w.bb_stop().enabled());
twi.tasks_resume.write(|w| unsafe { w.bits(1) });
while twi.events_rxdready.read().bits() == 0 {}
data[5] = twi.rxd.read().bits() as u8;
twi.events_rxdready.write(|w| unsafe { w.bits(0) });
/* Join and translate 2s complement values */
let (x, y, z) = (
(u16::from(data[0]) << 8 | u16::from(data[1])) as i16,
(u16::from(data[2]) << 8 | u16::from(data[3])) as i16,
(u16::from(data[4]) << 8 | u16::from(data[5])) as i16,
);
/* Print read values on the serial console */
if let Some(uart) = UART.borrow(cs).borrow().as_ref() {
let _ = write!(UART0Buffer(uart), "x: {}, y: {}, z: {}\n\r", x, y, z);
}
/* Clear timer event */
rtc.events_tick.write(|w| unsafe { w.bits(0) });
}
});
loop {
continue;
}
}
pub struct UART0Buffer<'a>(pub &'a UART0);
impl<'a> core::fmt::Write for UART0Buffer<'a> {
fn write_str(&mut self, s: &str) -> core::fmt::Result {
let uart0 = self.0;
uart0.tasks_starttx.write(|w| unsafe { w.bits(1) });
for c in s.as_bytes() {
/* Write the current character to the output register */
uart0.txd.write(|w| unsafe { w.bits(u32::from(*c)) });
/* Wait until the UART is clear to send */
while uart0.events_txdrdy.read().bits() == 0 {}
/* And then set it back to 0 again, just because ?!? */
uart0.events_txdrdy.write(|w| unsafe { w.bits(0) });
}
uart0.tasks_stoptx.write(|w| unsafe { w.bits(1) });
Ok(())
}
}
我认为这是地址问题，因为我在这里找到了不同的磁力计地址
所以，正如你可能猜到的，改变这条线
twi.address.write(|w| unsafe { w.address().bits(0x0E) });
至
twi.address.write(|w| unsafe { w.address().bits(0x1E) });
没有帮助，但是，出现了这条消息
x:0, y: 0, z: 0
我真的是硬件编程的新手，所以我可以使用任何帮助