Crate svd2rust [−] [src]
Peripheral API generator from CMSIS-SVD files
A SVD file is an XML file that describes the hardware features of a microcontroller. In particular, it list all the peripherals available to the device, where the registers associated to each device are located in memory and what's the function of each register.
svd2rust
is a command line tool that transforms SVD files into crates that
expose a type safe API to access the peripherals of the device.
Installation
$ cargo install svd2rust
Usage
$ svd2rust -i STM32F30x.svd | rustfmt | tee src/lib.rs //! Peripheral access API for STM32F30X microcontrollers (generated using svd2rust v0.4.0) #![deny(missing_docs)] #![deny(warnings)] #![feature(const_fn)] #![no_std] extern crate cortex_m; extern crate vcell; use cortex_m::peripheral::Peripheral; /// Interrupts pub mod interrupt { .. } /// General-purpose I/Os pub const GPIOA: Peripheral<Gpioa> = unsafe { Peripheral::new(1207959552) }; /// General-purpose I/Os pub mod gpioa { pub struct RegisterBlock { /// GPIO port mode register pub moder: Moder, .. } .. } pub use gpioa::RegisterBlock as Gpioa; /// General-purpose I/Os pub const GPIOB: Peripheral<Gpiob> = unsafe { Peripheral::new(1207960576) }; /// General-purpose I/Os pub mod gpiob { .. } pub use gpiob::RegisterBlock as Gpiob; /// GPIOC pub const GPIOC: Peripheral<Gpioc> = unsafe { Peripheral::new(1207961600) }; /// Register block pub type Gpioc = Gpiob; ..
Dependencies
The generated API depends on:
Peripheral API
In the root of the generated API, you'll find all the device peripherals as
const
ant struct
s. You can access the register block behind the
peripheral using either of these two methods:
get()
forunsafe
, unsynchronized access to the peripheral, orborrow()
which grants you exclusive access to the peripheral but can only be used within a critical section (interrupt::free
).
The register block is basically a struct
where each field represents a
register.
/// Inter-integrated circuit pub mod i2C1 /// Register block pub struct RegisterBlock { /// 0x00 - Control register 1 pub cr1: Cr1, /// 0x04 - Control register 2 pub cr2: Cr2, /// 0x08 - Own address register 1 pub oar1: Oar1, /// 0x0c - Own address register 2 pub oar2: Oar2, /// 0x10 - Timing register pub timingr: Timingr, /// Status register 1 pub timeoutr: Timeoutr, /// Interrupt and Status register pub isr: Isr, /// 0x1c - Interrupt clear register pub icr: Icr, /// 0x20 - PEC register pub pecr: Pecr, /// 0x24 - Receive data register pub rxdr: Rxdr, /// 0x28 - Transmit data register pub txdr: Txdr, } }
read
/ modify
/ write
API
Each register in the register block, e.g. the cr1
field in the I2c
struct, exposes a combination of the read
, modify
and write
methods.
Which methods exposes each register depends on whether the register is
read-only, read-write or write-only:
- read-only registers only expose the
read
method. - write-only registers only expose the
write
method. - read-write registers expose all the methods:
read
,modify
andwrite
.
This is signature of each of these methods:
(using I2C
's CR2
register as an example)
impl Cr2 { /// Modifies the contents of the register pub fn modify<F>(&mut self, f: F) where for<'w> F: FnOnce(&R, &'w mut W) -> &'w mut W { .. } /// Reads the contents of the register pub fn read(&self) -> R { .. } /// Writes to the register pub fn write<F>(&mut self, f: F) where F: FnOnce(&mut W) -> &mut W, { .. } }
The read
method "reads" the register using a single, volatile LDR
instruction and returns a proxy R
struct that allows access to only the
readable bits (i.e. not to the reserved or write-only bits) of the CR2
register:
/// Value read from the register impl R { /// Bit 0 - Slave address bit 0 (master mode) pub fn sadd0(&self) -> Sadd0R { .. } /// Bits 1:7 - Slave address bit 7:1 (master mode) pub fn sadd1(&self) -> Sadd1R { .. } (..) }
Usage looks like this:
// is the SADD0 bit of the CR2 register set? if i2c1.c2r.read().sadd0().bits() == 1 { // yes } else { // no }
On the other hand, the write
method writes some value to the register
using a single, volatile STR
instruction. This method involves a W
struct that only allows constructing valid states of the CR2
register.
The only constructor that W
provides is reset_value
which returns the
value of the CR2
register after a reset. The rest of W
methods are
"builder-like" and can be used to modify the writable bitfields of the
CR2
register.
impl Cr2W { /// Reset value pub fn reset_value() -> Self { Cr2W { bits: 0 } } /// Bits 1:7 - Slave address bit 7:1 (master mode) pub fn sadd1(&mut self) -> _Sadd1W { .. } /// Bit 0 - Slave address bit 0 (master mode) pub fn sadd0(&mut self) -> _Sadd0 { .. } }
The write
method takes a closure with signature (&mut W) -> &mut W
. If
the "identity closure", |w| w
, is passed then the write
method will set
the CR2
register to its reset value. Otherwise, the closure specifies how
the reset value will be modified before it's written to CR2
.
Usage looks like this:
// Starting from the reset value, `0x0000_0000`, change the bitfields SADD0 // and SADD1 to `1` and `0b0011110` respectively and write that to the // register CR2. i2c1.cr2.write(|w| unsafe { w.sadd0().bits(1).sadd1().bits(0b0011110) }); // NOTE ^ unsafe because you could be writing a reserved bit pattern into // the register. In this case, the SVD doesn't provide enough information to // check whether that's the case. // NOTE The argument to `bits` will be *masked* before writing it to the // bitfield. This makes it impossible to write, for example, `6` to a 2-bit // field; instead, `6 & 3` (i.e. `2`) will be written to the bitfield.
Finally, the modify
method performs a single read-modify-write
operation that involves one read (LDR
) to the register, modifying the
value and then a single write (STR
) of the modified value to the
register. This method accepts a closure that specifies how the CR2 register
will be modified (the w
argument) and also provides access to the state of
the register before it's modified (the r
argument).
Usage looks like this:
// Set the START bit to 1 while KEEPING the state of the other bits intact i2c1.cr2.modify(|_, w| unsafe { w.start().bits(1) }); // TOGGLE the STOP bit, all the other bits will remain untouched i2c1.cr2.modify(|r, w| w.stop().bits(r.stop().bits() ^ 1));
enumeratedValues
If your SVD uses the <enumeratedValues>
feature, then the API will be
extended to provide even more type safety. This extension is backward
compatible with the original version so you could "upgrade" your SVD by
adding, yourself, <enumeratedValues>
to it and then use svd2rust
to
re-generate a better API that doesn't break the existing code that uses
that API.
The new read
API returns an enum that you can match:
match gpioa.dir.read().pin0() { gpioa::dir::Pin0R::Input => { .. }, gpioa::dir::Pin0R::Output => { .. }, }
or test for equality
if gpioa.dir.read().pin0() == gpio::dir::Pin0R::Input { .. }
It also provides convenience methods to check for a specific variant without having to import the enum:
if gpioa.dir.read().pin0().is_input() { .. } if gpioa.dir.read().pin0().is_output() { .. }
The original bits
method is available as well:
if gpioa.dir.read().pin0().bits() == 0 { .. }
And the new write
API provides similar additions as well: variant
lets
you pick the value to write from an enum
eration of the possible ones:
// enum DirW { Input, Output } gpioa.dir.write(|w| w.pin0().variant(gpio::dir::Pin0W::Output));
There are convenience methods to pick one of the variants without having to import the enum:
gpioa.dir.write(|w| w.pin0().output());
The bits
method is still available but will become safe if it's impossible
to write a reserved bit pattern into the register
// safe because there are only two options: `0` or `1` gpioa.dir.write(|w| w.pin0().bits(1));
Interrupt API
SVD files also describe the interrupts available to the device. Binary output
wise, the interrupt handlers must be stored in the vector table region of
Flash memory. svd2rust
provides an API to easily "register" interrupt
handlers.
/// Interrupts pub mod interrupt { /// Interrupt handlers pub struct Handlers { /// Window Watchdog interrupt pub wwdg: unsafe extern "C" fn(Wwdg), /// PVD through EXTI line detection interrupt pub pvd: unsafe extern "C" fn(Pvd), .. } pub const DEFAULT_HANDLERS: Handlers = Handlers { wwdg: exception::default_handler, pvd: exception::default_handler, .. }; }
This Handlers
API then can be used in applications to register the
interrupt handlers:
fn main() { .. } // My interrupt handler extern "C" fn tim7(_: interrupt::Tim7) { .. } #[no_mangle] pub static _INTERRUPT: interrupt::Handlers = interrupt::Handlers { tim7: tim7, ..interrupt::DEFAULT_HANDLERS }
This requires some linker script support:
SECTIONS { .text ORIGIN(FLASH) : { /* Vector table */ LONG(ORIGIN(RAM) + LENGTH(RAM)); /* Initial SP value */ LONG(__reset + 1); /* Reset handler */ KEEP(*(.rodata._EXCEPTIONS)); /* exception handlers */ KEEP(*(.rodata._INTERRUPTS)); /* interrupt handlers */ .. } .. }
The generated API also includes an Interrupt
enum
pub mod interrupt { /// Enumeration of all the interrupts pub enum Interrupt { Wwdg, Pvd, .. } }
that can be used with cortex-m
's NVIC API:
interrupt::free(|cs| { NVIC.borrow(&cs).enable(Interrupt::Tim3); NVIC.borrow(&cs).enable(Interrupt::Tim7); });