More specifically, the build system now uses the semantic versioning meta-data
held in module.json to define a major.minor.patch version. Additionally, is the branch
being compiled is *not* the master branch, the version is appended with <branchname><githash>.
Specific updates:
- Updates to CMake files to expose this to the micro:bit runtime code.
- Addition of uBit.systemVersion() to expose this to application code.
- Displaying of version string over serial if MICROBIT_DBG is enabled.
- Distribution of version string over BLE via the firmware revision characteristic.
- renamed fiber flag to be more general.
- renamed idle to idleFiber to be consistent with the rest of the code.
- factored content of idle() into a funciton to avoid dupication.
- added test case to MessageBus::process() to avoid forking fibers if not requested.
- removed fiber_allow_run_idle_within mutator in favour of exposing currentFiber, as a more general solution.
If there is only 1 main fiber (plus the idle fiber) then enabling this
new feature for the main fiber (using fiber_allow_run_idle_within())
will mean that no heap is needed to swap the stack out.
Corrected corner case memory leak. Instances of ManagedType<> created using the default
constructor would create a reference counter by default, with a value of 0. However, if
destructor or copy-assigned in this state, this reference count would not be destroyed,
resulting in a 4 byte leak on the heap for each occurence.
Hotfix of a minor bug in the MicroBitDFU Service that prevented BLE notifications
from being sent on the FlashCode characterisitic. Needed as the Samsung companion
app is dependent on this functionality to enable BLE programmming of the micro:bit.
Events in the micro:bit runtime are normally launched through making an instance
of the MicroBitEvent class. This update added configuration support to all the
code creating the MicroBitEvent decide if the newly created event should then be
automatically queued on the MessageBus or processed immediately by event handlers.
MessageBus handlers can now have one of four concurrency modes for the eventuality
of an event being raised whilst a previous event is still being processed. An additional
(optional) parameter is provided to the listen() functions to allow this to be selected
on a per event handler basis. The permissable options are:
MESSAGE_BUS_LISTENER_REENTRANT:
The event handler is fired with the new event, regardless of whether or not
a previous event is still be processed by that handler.
MESSAGE_BUS_LISTENER_QUEUE_IF_BUSY:
The new event is queued until such a time as the previous event has completed
execution. The new event is then processed. This option does not preclude the
processing of the new event by other event handlers.
MESSAGE_BUS_LISTENER_DROP_IF_BUSY:
The new event is dropped, and will never be processed the the event handler.
This option does not preclude the processing of the new event by other event handlers.
MESSAGE_BUS_LISTENER_NONBLOCKING:
The event handler is self-declaring that it never blocks. This flag is used purely
for optimisation, as it permits direct execution of the event hadnelr without inducing
any overhead from the scheduler.
In addition, the following minor revisions were made in this release:
* Cleanup of the #include dependencies contained in the microbit-dal .h files
* Bugfix to the scheduler block on event matching code.
* Introduced a MICROBIT_ID_ALERT MessageBus channel, for general purpose eventing using nonces.
A header file containing custom configuration options for the microbit:runtime can
now be defined through a yotaa configuration option.
For example, including the following inside a top level config.json file
will load configuration options from a file called "MicroBitCustomConfig.h" that is stored
alongside an application's main.cpp. Any options defined there will override the defaults
defined in microbit-dal/inc/MicroBitConfig.h :
{
"microbit" :{
"configfile" : "source/MicroBitCustomConfig.h"
}
}
All options defined in MicroBitConfig are now set IFF they already do not have a value.
This allows external configuration of these options much more cleanly. Additional macros
also defined to provide clean implementation for boolean configuration switches.
Also some minor bugfixes:
- Correction of typo of "Microbit.h" => "MicroBit.h"
- Fixed heap corruption bug on gcc as a result of a debug printf in an unsafe context.
This release contains a widespread set of updates and optimisations to the micro:bit
runtime, with a view to reducing the SRAM footprint of the whole system. This is to
provide as much usable HEAP storage for application programs as possible.
Specific updates and optimisations include:
- Additional compilation flags to allow the core micro:bit runtime to be configured.
These are defined in MicroBitConfig.h
- A custom heap allocator. This is now included for two reasons:
1) To provide a simple mechanism to to utilise both the mbed heap space and other memory
regions (such as unused memory in the SoftDevice region) as a single virtual heap.
2) To address some issues that have been noted that are attributable to heap fragmentation.
The micro:bit heap allocator has a simple algorithm, but one that is chosen to respond
well to the relativelt high 'heap churn' found in the micro:bit environment.
All micro:bit components and user programs now use this heap allocator trasparently.
- Updates to BLE services to remove persistent references to their GATT services. This consumes
vast amounts SRAM, rather unecessarily. Instead only handles to the relevant GATT characteristics
are now stored. This specifically includes:
+ MicroBitDFUService
+ MicroBitEventService
+ DeviceInformationService
- Updates to the Fiber scheduler to save SRAM. More specifically:
+ Removed the need to hold an empty processor context to intialise fibers.
+ The IDLE fiber now runs without a stack
+ fiber stacks are now only created when a fiber is descheduled for the first time, thereby reducing heap churn.
+ the 'main' fiber is now recycled into the fiber_pool if it leaves app_main()
+ fibers created through invoke() now only maintains the necessary part of teh parent stack that is needed, thereby
reducing the stack size of spawned fibers.
- Updates to the Message Bus to reduce the overall memory footprint of processing events. More specifically:
+ Event handlers are now always called using invoke(), such that non-blocking event handlers no longer need
a dedicated fiber to execute - thereby saving SRAM and processor time.
+ Processing of events from the event queue is now rate paced. Events only continue to be processed as long as there
are no fibers on the run queue. i.e. event processing is no longer greedy, thereby reducing the number of fibers
created on the runqueue.
- Updates to BLUEZOENE code to bring up core BLE services even if they are not enabled by default. This allows
programs that do not require BLE to operate to benefit from the full range of SRAM, whilst still allowing the
device to be programmed over BLE.
- Updates to the Soft Device initialisation configuration, reducing the size of the GATT table held in the top 1.8K
of its 8K memory region to around 800 bytes. This is sufficient to run the default set of BLE services on the micro:bit
so the additional memory is configured as HEAP storage by MicroBitHeapAllocator.
- Minor changes to a range of components to integrate with the above changes.
+ rename of free() to release() in DynamicPWM to avoid namespace collision with MicroBitHeap free()
+ rename of fork_on_block to invoke() to enhance readbility.
- Many code cleanups and updates to out of date comments.
Updates to MicroBitDisplay::setBrightness() to perform a NOP for out of bound parameters.
This aligns the functionality of the runtime with the TD simulator.
Updates the MicroBitMessageBus implementation to use fork_on_block() calls rather
than create_fiber() calls when servicing events. This provides greater optimisation
for non-blocking event handlers.
More specifically, this update:
- Replaces calls to create_fiber() ith fork_on_block during event send operations.
- Adds a queue of events, to ensure events generated from interrupt context are not serviced in interrupt context.
- Registers a listener with the idle process to empty the event queue.
The microbit fiber scheduler is often used to service event handlers by the microbit message bus.
This provides a very elegant decoupling of user code from system code, interrupt handlers and
also allows users to make blocking calls within event handlers. However, many event handlers are
non-blocking, so launching a dedicated fiber is wasteful in terms of time and SRAM.
This patch adds fork_on_block() to the scheduler. Inspired by the UNIX copy_on_write
technique, this optimisation is semantically equivalent to a create_fiber() call, but will first attempt
to execute the given function in the context of the currently running fiber, and *only* create a fiber
if the given code attempts a blocking operation.
More specifically, this update:
- adds fork_on_block() functions for parameterised and non-parameterised functions.
- adds fields to the fiber context to record the status of parent/child fibers.
- adds optimised ASM functions to store and restore Cortex M0 register context.
- adds a utility function to determine if the processor is executing in interrupt context.
- updates to sleep() and wait_for_event() to handle fork_on_block semantics.
- minor code optimsations within the scheduler.
NO_BLE can now be defined to determine whether ble
will be brought up or not at initialisation of uBit.
This is especially useful for two new Yotta targets:
bbc-microbit-classic-gcc-nosd,
bbc-microbit-classic-armcc-nosd, which do not use
softdevice.
This is the first commit of the microbit-dal on GitHub.
This repository contains the runtime, which is a light
weight operating system developed by Lancaster University.
Joe Finney