shared-bus is a crate to allow sharing bus peripherals safely between multiple devices.
In the embedded-hal ecosystem, it is convention for drivers to "own" the bus peripheral they are operating on. This implies that only one driver can have access to a certain bus. That, of course, poses an issue when multiple devices are connected to a single bus.
shared-bus solves this by giving each driver a bus-proxy to own which internally manages access to the actual bus in a safe manner. For a more in-depth introduction of the problem this crate is trying to solve, take a look at the blog post.
There are different 'bus managers' for different use-cases:
Sharing within a single task/threadAs long as all users of a bus are contained in a single task/thread, bus sharing is very simple. With no concurrency possible, no special synchronization is needed. This is where a BusManagerSimple should be used:
// For example: let i2c = I2c::i2c1(dp.I2C1, (scl, sda), 90.khz(), clocks, &mut rcc.apb1); let bus = shared_bus::BusManagerSimple::new(i2c); let mut proxy1 = bus.acquire_i2c(); let mut my_device = MyDevice::new(bus.acquire_i2c()); proxy1.write(0x39, &[0xc0, 0xff, 0xee]); my_device.do_something_on_the_bus();
The BusManager::acquire_*() methods can be called as often as needed; each call will yield a new bus-proxy of the requested type.
For sharing across multiple tasks/threads, synchronization is needed to ensure all bus-accesses are strictly serialized and can't race against each other. The synchronization is handled by a platform-specific BusMutex implementation. shared-bus already contains some implementations for common targets. For each one, there is also a macro for easily creating a bus-manager with 'static lifetime, which is almost always a requirement when sharing across task/thread boundaries. As an example:
// For example:
let i2c = I2c::i2c1(dp.I2C1, (scl, sda), 90.khz(), clocks, &mut rcc.apb1);
// The bus is a 'static reference -> it lives forever and references can be
// shared with other threads.
let bus: &'static _ = shared_bus::new_std!(SomeI2cBus = i2c).unwrap();
let mut proxy1 = bus.acquire_i2c();
let mut my_device = MyDevice::new(bus.acquire_i2c());
// We can easily move a proxy to another thread:
# let t =
std::thread::spawn(move || {
my_device.do_something_on_the_bus();
});
# t.join().unwrap();
Those platform-specific bits are guarded by a feature that needs to be enabled. Here is an overview of what's already available:
Currently, the following busses can be shared with shared-bus:
shared-bus is licensed under either of
at your option.
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