embedded_hal_bus/i2c/
critical_section.rs

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1use core::cell::RefCell;
2use critical_section::Mutex;
3use embedded_hal::i2c::{ErrorType, I2c};
4
5/// `critical-section`-based shared bus [`I2c`] implementation.
6///
7/// Sharing is implemented with a `critical-section` [`Mutex`]. A critical section is taken for
8/// the entire duration of a transaction. This allows sharing a single bus across multiple threads (interrupt priority levels).
9/// The downside is critical sections typically require globally disabling interrupts, so `CriticalSectionDevice` will likely
10/// negatively impact real-time properties, such as interrupt latency. If you can, prefer using
11/// [`RefCellDevice`](super::RefCellDevice) instead, which does not require taking critical sections.
12pub struct CriticalSectionDevice<'a, T> {
13    bus: &'a Mutex<RefCell<T>>,
14}
15
16impl<'a, T> CriticalSectionDevice<'a, T> {
17    /// Create a new `CriticalSectionDevice`.
18    #[inline]
19    pub fn new(bus: &'a Mutex<RefCell<T>>) -> Self {
20        Self { bus }
21    }
22}
23
24impl<'a, T> ErrorType for CriticalSectionDevice<'a, T>
25where
26    T: I2c,
27{
28    type Error = T::Error;
29}
30
31impl<'a, T> I2c for CriticalSectionDevice<'a, T>
32where
33    T: I2c,
34{
35    #[inline]
36    fn read(&mut self, address: u8, read: &mut [u8]) -> Result<(), Self::Error> {
37        critical_section::with(|cs| {
38            let bus = &mut *self.bus.borrow_ref_mut(cs);
39            bus.read(address, read)
40        })
41    }
42
43    #[inline]
44    fn write(&mut self, address: u8, write: &[u8]) -> Result<(), Self::Error> {
45        critical_section::with(|cs| {
46            let bus = &mut *self.bus.borrow_ref_mut(cs);
47            bus.write(address, write)
48        })
49    }
50
51    #[inline]
52    fn write_read(
53        &mut self,
54        address: u8,
55        write: &[u8],
56        read: &mut [u8],
57    ) -> Result<(), Self::Error> {
58        critical_section::with(|cs| {
59            let bus = &mut *self.bus.borrow_ref_mut(cs);
60            bus.write_read(address, write, read)
61        })
62    }
63
64    #[inline]
65    fn transaction(
66        &mut self,
67        address: u8,
68        operations: &mut [embedded_hal::i2c::Operation<'_>],
69    ) -> Result<(), Self::Error> {
70        critical_section::with(|cs| {
71            let bus = &mut *self.bus.borrow_ref_mut(cs);
72            bus.transaction(address, operations)
73        })
74    }
75}
embedded_hal_bus/i2c/critical_section.rs

embedded_hal_bus/i2c/
critical_section.rs
