Crate embassy_nrf
source ·Expand description
§Embassy nRF HAL
HALs implement safe, idiomatic Rust APIs to use the hardware capabilities, so raw register manipulation is not needed.
The Embassy nRF HAL targets the Nordic Semiconductor nRF family of hardware. The HAL implements both blocking and async APIs for many peripherals. The benefit of using the async APIs is that the HAL takes care of waiting for peripherals to complete operations in low power mode and handling interrupts, so that applications can focus on more important matters.
NOTE: The Embassy HALs can be used both for non-async and async operations. For async, you can choose which runtime you want to use.
For a complete list of available peripherals and features, see the embassy-nrf documentation.
§Hardware support
The embassy-nrf
HAL supports most variants of the nRF family:
Most peripherals are supported, but can vary between chip families. To check what’s available, make sure to pick the MCU you’re targeting in the top menu in the documentation.
For MCUs with TrustZone support, both Secure (S) and Non-Secure (NS) modes are supported. Running in Secure mode allows running Rust code without a SPM or TF-M binary, saving flash space and simplifying development.
§Time driver
If the time-driver-rtc1
feature is enabled, the HAL uses the RTC peripheral as a global time driver for embassy-time, with a tick rate of 32768 Hz.
§Embedded-hal
The embassy-nrf
HAL implements the traits from embedded-hal (v0.2 and 1.0) and embedded-hal-async, as well as embedded-io and embedded-io-async.
§Interoperability
This crate can run on any executor.
Optionally, some features requiring embassy-time
can be activated with the time
feature. If you enable it,
you must link an embassy-time
driver in your project.
§EasyDMA considerations
On nRF chips, peripherals can use the so called EasyDMA feature to offload the task of interacting with peripherals. It takes care of sending/receiving data over a variety of bus protocols (TWI/I2C, UART, SPI). However, EasyDMA requires the buffers used to transmit and receive data to reside in RAM. Unfortunately, Rust slices will not always do so. The following example using the SPI peripheral shows a common situation where this might happen:
// As we pass a slice to the function whose contents will not ever change,
// the compiler writes it into the flash and thus the pointer to it will
// reference static memory. Since EasyDMA requires slices to reside in RAM,
// this function call will fail.
let result = spim.write_from_ram(&[1, 2, 3]);
assert_eq!(result, Err(Error::BufferNotInRAM));
// The data is still static and located in flash. However, since we are assigning
// it to a variable, the compiler will load it into memory. Passing a reference to the
// variable will yield a pointer that references dynamic memory, thus making EasyDMA happy.
// This function call succeeds.
let data = [1, 2, 3];
let result = spim.write_from_ram(&data);
assert!(result.is_ok());
Each peripheral struct which uses EasyDMA (Spim
, Uarte
, Twim
) has two variants of their mutating functions:
- Functions with the suffix (e.g.
write_from_ram
,transfer_from_ram
) will return an error if the passed slice does not reside in RAM. - Functions without the suffix (e.g.
write
,transfer
) will check whether the data is in RAM and copy it into memory prior to transmission.
Since copying incurs a overhead, you are given the option to choose from _from_ram
variants which will
fail and notify you, or the more convenient versions without the suffix which are potentially a little bit
more inefficient. Be aware that this overhead is not only in terms of instruction count but also in terms of memory usage
as the methods without the suffix will be allocating a statically sized buffer (up to 512 bytes for the nRF52840).
Note that the methods that read data like read
and transfer_in_place
do not have the corresponding _from_ram
variants as
mutable slices always reside in RAM.
§Feature flags
rt
(enabled by default) — Cortex-M runtime (enabled by default)time
— Enable features requiringembassy-time
defmt
— Enable defmtunstable-pac
— Reexport the PAC for the currently enabled chip atembassy_nrf::pac
(unstable)gpiote
— Enable GPIO tasks and eventstime-driver-rtc1
— Use RTC1 as the time driver forembassy-time
, with a tick rate of 32.768khznfc-pins-as-gpio
— Allow using the NFC pins as regular GPIO pins (P0_09/P0_10 on nRF52, P0_02/P0_03 on nRF53)reset-pin-as-gpio
— Allow using the RST pin as a regular GPIO pin.- nRF52805, nRF52810, nRF52811, nRF52832: P0_21
- nRF52820, nRF52833, nRF52840: P0_18
qspi-multiwrite-flash
— Implements the MultiwriteNorFlash trait for QSPI. Should only be enabled if your external flash supports the semantics described here
§Chip selection features
nrf51
— nRF51nrf52805
— nRF52805nrf52810
— nRF52810nrf52811
— nRF52811nrf52820
— nRF52820nrf52832
— nRF52832nrf52833
— nRF52833nrf52840
— nRF52840nrf5340-app-s
— nRF5340 application core in Secure modenrf5340-app-ns
— nRF5340 application core in Non-Secure modenrf5340-net
— nRF5340 network corenrf9160-s
— nRF9160 in Secure modenrf9160-ns
— nRF9160 in Non-Secure modenrf9120-s
— The nRF9120 is the internal part number for the nRF9161 and nRF9151. nRF9120 in Secure modenrf9120-ns
— nRF9120 in Non-Secure mode
Re-exports§
pub use chip::pac;
Modules§
- Async buffered UART driver.
- Configuration options used when initializing the HAL.
- EGU driver.
- General purpose input/output (GPIO) driver.
- GPIO task/event (GPIOTE) driver.
- Inter-IC Sound (I2S) driver.
- Interrupt definitions.
- Non-Volatile Memory Controller (NVMC, AKA internal flash) driver.
- Pulse Density Modulation (PDM) microphone driver
- Types for the peripheral singletons.
- Programmable Peripheral Interconnect (PPI/DPPI) driver.
- Pulse Width Modulation (PWM) driver.
- Quadrature decoder (QDEC) driver.
- Integrated 2.4 GHz Radio
- Random Number Generator (RNG) driver.
- Successive Approximation Analog-to-Digital Converter (SAADC) driver.
- Serial Peripheral Instance in master mode (SPIM) driver.
- Serial Peripheral Instance in slave mode (SPIS) driver.
- Builtin temperature sensor driver.
- Timer driver.
- I2C-compatible Two Wire Interface in master mode (TWIM) driver.
- I2C-compatible Two Wire Interface in slave mode (TWIM) driver.
- Universal Asynchronous Receiver Transmitter (UART) driver.
- Watchdog Timer (WDT) driver.
Macros§
- Macro to bind interrupts to handlers.
- Convenience converting into reference.
Structs§
- An exclusive reference to a peripheral.
- Struct containing all the peripheral singletons.
Constants§
- The maximum buffer size that the EasyDMA can send/recv in one operation.
- Number available in the NVIC for configuring priority
Traits§
- Trait for any type that can be used as a peripheral of type
P
.
Functions§
- Initialize the
embassy-nrf
HAL with the provided configuration.