It was intended to allow changing baudrate on shared spi/i2c. There's no
advantage in using it for PWM or PIO, and makes it less usable because you have to
have `embassy-embedded-hal` as a dep to use it.
execution wraps around after the end of instruction memory and wrapping
works with this, so we may as well allow program loading across this
boundary. could be useful for reusing chunks of instruction memory.
the many individual sets aren't very efficient, and almost no checks
were done to ensure that the configuration written to the hardware was
actually valid. this adresses both of these.
programs contain information we could pull from them directly and use to
validate other configuration of the state machine instead of asking the
user to pull them out and hand them to us bit by bit. unfortunately
programs do not specify how many in or out bits they use, so we can only
handle side-set and wrapping jumps like this. it's still something though.
it's only any good for PioPin because there it follows a pattern of gpio
pin alternate functions being named like that, everything else can just
as well be referred to as `pio::Thing`
this *finally* allows sound implementions of bidirectional transfers
without blocking. the futures previously allowed only a single direction
to be active at any given time, and the dma transfers didn't take a
mutable reference and were thus unsound.
we can only have one active waiter for any given irq at any given time.
allowing waits for irqs on state machines bypasses this limitation and
causes lost events for all but the latest waiter for a given irq.
splitting this out also allows us to signal from state machines to other
parts of the application without monopolizing state machine access for
the irq wait, as would be necessary to make irq waiting sound.
move all methods into PioStateMachine instead. the huge trait wasn't
object-safe and thus didn't have any benefits whatsoever except for
making it *slightly* easier to write bounds for passing around state
machines. that would be much better solved with generics-less instances.
not requiring a PioInstance for splitting lets us split from a
PeripheralRef or borrowed PIO as well, mirroring every other peripheral
in embassy_rp. pio pins still have to be constructed from owned pin
instances for now.
merge into PioInstance instead. PioPeripheral was mostly a wrapper
around PioInstance anyway, and the way the wrapping was done required
PioInstanceBase<N> types where PIO{N} could've been used instead.
add an hd44780 example for pio. hd44780 with busy polling is a pretty
complicated protocol if the busy polling is to be done by the
peripheral, and this example exercises many pio features that we don't
have good examples for yet.
1414: rp: report errors from buffered and dma uart receives r=Dirbaio a=pennae
neither of these reported errors so far, which is not ideal. add error reporting to both of them that matches the blocking error reporting as closely as is feasible, even allowing partial receives from buffered uarts before errors are reported where they would have been by the blocking code. dma transfers don't do this, if an errors applies to any byte in a transfer the entire transfer is nuked (though we probably could report how many bytes have been transferred).
Co-authored-by: pennae <github@quasiparticle.net>
instruction memory is a shared resource. writing it only from PioCommon
clarifies this, and perhaps makes it more obvious that multiple state
machines can share the same instructions.
this also allows *freeing* of instruction memory to reprogram the
system, although this interface is not entirely safe yet. it's safe in
the sense rusts understands things, but state machines may misbehave if
their instruction memory is freed and rewritten while they are running.
fixing this is out of scope for now since it requires some larger
changes to how state machines are handled. the interface provided
currently is already unsafe in that it lets people execute instruction
memory that has never been written, so this isn't much of a drawback for now.
pin and irq operations affect the entire pio block. with pins this is
not very problematic since pins themselves are resources, but irqs are
not treated like that and can thus interfere across state machines. the
ability to wait for an irq on a state machine is kept to make
synchronization with user code easier, and since we can't inspect loaded
programs at build time we wouldn't gain much from disallowing waits from
state machines anyway.
inline assembly is supported since rust 1.59, we're way past that.
enabling this makes the compiled code more compact, and on rp2040
even decreses memory usage by not needing thunks in sram.
This introduces a `Pender` struct with enum cases for thread-mode, interrupt-mode and
custom callback executors. This avoids calls through function pointers when using only
the thread or interrupt executors. Faster, and friendlier to `cargo-call-stack`.
`embassy-executor` now has `arch-xxx` Cargo features to select the arch and to enable
the builtin executors (thread and interrupt).
This example also uses a pio program compiled at runtime, rather than one built at compile time. There's no reason to do that, but it's probably useful to have an example that does this as well.
- Allows classes to handle vendor requests.
- Allows classes to use a single handler for multiple interfaces.
- Allows classes to access the other events (previously only `reset` was available).
1142: More rp2040 BufferedUart fixes r=Dirbaio a=timokroeger
* Refactor init code
* Make it possible to drop RX without breaking TX (or vice versa)
* Correctly handle RX buffer full scenario
Co-authored-by: Timo Kröger <timokroeger93@gmail.com>
