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
supports Cortex-M and MSP430 microcontrollers. The generated
crate can be tailored for either architecture using the --target
flag. The
flag accepts "cortex-m", "msp430" and "none" as values. "none" can be used
to generate a crate that's architecture agnostic and that should work for
architectures that svd2rust
doesn't currently know about like the Cortex-A
architecture.
If the --target
flag is omitted svd2rust
assumes the target is the
Cortex-M architecture.
$ svd2rust -i STM32F30x.svd | rustfmt | tee src/lib.rs //! Peripheral access API for STM32F30X microcontrollers //! (generated using svd2rust v0.12.0) #![deny(missing_docs)] #![deny(warnings)] #![no_std] extern crate bare_metal; extern crate cortex_m; #[cfg(feature = "rt")] extern crate cortex_m_rt; extern crate vcell; use cortex_m::peripheral::Peripheral; /// Interrupts pub mod interrupt { // .. } /// General-purpose I/Os pub mod gpioa { pub struct RegisterBlock { /// GPIO port mode register pub moder: MODER, .. } .. } /// General-purpose I/Os pub struct GPIOA { _marker: PhantomData<*const ()> } unsafe impl Send for GPIOA {} impl GPIOA { /// Returns a pointer to the register block pub fn ptr() -> *const gpioa::RegisterBlock { 0x4800_0000 as *const _ } } impl core::ops::Deref for GPIOA { type Target = gpioa::RegisterBlock; fn deref(&self) -> &gpioa::RegisterBlock { unsafe { &*GPIOA::ptr() } } } // ..
Dependencies
The generated crate depends on:
bare-metal
v0.1.xvcell
v0.1.xcortex-m-rt
v0.4.x if targeting the Cortex-M architecture.cortex-m
v0.4.x if targeting the Cortex-M architecture.msp430
v0.1.x if targeting the MSP430 architecture.msp430-rt
v0.1.x if targeting the MSP430 architecture.
Peripheral API
To use a peripheral first you must get an instance of the peripheral. All the device
peripherals are modeled as singletons (there can only ever be, at most, one instance of any
one of them) and the only way to get an instance of them is through the Peripherals::take
method.
fn main() { let mut peripherals = stm32f30x::Peripherals::take().unwrap(); peripherals.GPIOA.odr.write(|w| w.bits(1)); }
This method can only be successfully called once -- that's why the method returns an Option
.
Subsequent calls to the method will result in a None
value being returned.
fn main() { let ok = stm32f30x::Peripherals::take().unwrap(); let panics = stm32f30x::Peripherals::take().unwrap(); }
The singleton property can be unsafely bypassed using the ptr
static method which is
available on all the peripheral types. This method is a useful for implementing safe higher
level abstractions.
struct PA0 { _0: () } impl PA0 { fn is_high(&self) -> bool { // NOTE(unsafe) actually safe because this is an atomic read with no side effects unsafe { (*GPIOA::ptr()).idr.read().bits() & 1 != 0 } } fn is_low(&self) -> bool { !self.is_high() } } struct PA1 { _0: () } // .. fn configure(gpioa: GPIOA) -> (PA0, PA1, ..) { // configure all the PAx pins as inputs gpioa.moder.reset(); // the GPIOA proxy is destroyed here now the GPIOA register block can't be modified // thus the configuration of the PAx pins is now frozen drop(gpioa); (PA0 { _0: () }, PA1 { _0: () }, ..) }
Each peripheral proxy deref
s to a RegisterBlock
struct that represents a piece of device
memory. Each field in this struct
represents one register in the register block associated to
the peripheral.
/// 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>(&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().bit() { // 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) -> SADD0R { .. } }
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().bit(true).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().bit(true) }); // TOGGLE the STOP bit, all the other bits will remain untouched i2c1.cr2.modify(|r, w| w.stop().bit(!r.stop().bit()));
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
(or bit
) 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().bit(true));
Interrupt API
SVD files also describe the device interrupts. svd2rust generated crates expose an enumeration
of the device interrupts as an Interrupt
enum
in the root of the crate. This enum
can be
used with the cortex-m
crate NVIC
API.
extern crate cortex_m; extern crate stm32f30x; use cortex_m::interrupt; use cortex_m::peripheral::Peripherals; use stm32f30x::Interrupt; let p = Peripherals::take().unwrap(); let mut nvic = p.NVIC; nvic.enable(Interrupt::TIM2); nvic.enable(Interrupt::TIM3);
the "rt" feature
If the "rt" Cargo feature of the svd2rust generated crate is enabled the crate will populate the
part of the vector table that contains the interrupt vectors and provide an
interrupt!
macro that can be used to register interrupt handlers.
Macros
interrupt |
Assigns a handler to an interrupt |