atomthreads/ports/stm8/README-IAR

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Library:      Atomthreads
Author:       Kelvin Lawson <info@atomthreads.com>
Website:      http://atomthreads.com
License:      BSD Revised

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STM8 PORT - IAR COMPILER

This folder contains a port of the Atomthreads real time kernel for the
STM8 processor architecture. These instructions cover usage of Atomthreads
with the IAR Embedded Workbench compiler (EWSTM8).

Compiler-agnostic aspects of the usage of Atomthreads can be found in README.

Instructions for users of the other compilers are available in README-SDCC,
README-COSMIC and README-RAISONANCE.


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PREREQUISITES

The port works out-of-the-box with the IAR compiler tools for building.
Applications are generated in ELF format and can be programmed and debugged
using the IAR Embedded Workbench GUI or the free STVP (visual programmer
tool). At this time there does not appear to be a command-line programmer
application suitable for use with STM8.

IAR Embedded Workbench for STM8 is a Windows-only application. For
users of other operating systems the IAR tools may work in environments
like Wine, but the USB programming tools are less likely to be supported.
Embedded Workbench for STM8 can, however, be run successfully within a VM
such as VirtualBox, including USB download and debug.

The core software prerequisites are therefore:
 * IAR Embedded Workbench STM8

Use with alternative compiler tools may require some modification, but you
can easily replace the EWSTM8 IDE by your own favourite programmer if
required (e.g. STVP).


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BUILDING THE SOURCE

You may build Atomthreads using whichever build environment you desire. For
your convenience we provide both a ready-rolled Makefile-based build system
and an Embedded Workbench (EWSTM8) project. The EWSTM8 project permits easy
building, programming and debugging, but does not easily support building
a wide range of application builds within the same project, which is
useful for building the numerous automated tests. For the automated tests
you may find it easier to use the Makefile which automatically builds all
automated tests.


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BUILD VIA EWSTM8 PROJECT

For building applications using the EWSTM8 IDE you can use the sample 
project file atomthreads-sample-iar.ewp. This builds a sample full
application which runs the "sem1" automated test. Applications can be
downloaded directly to the target hardware (e.g. STM8S-Discovery) and run
via the integrated debugger. You can start the application running, and
confirm that the LED flashes once per second (if running on an
STM8S-Discovery) to ensure that the test has passed. 

This is also a good starting point for building your own applications:
simply modify the file tests-main.c which starts the test application.
You can run any of the other automated tests by replacing the file sem1.c
within the project by another of the tests within the atomthreads tests
folder. This is rather painful using a GUI interface due to the large
number of test files, and you may prefer to use the Makefile-based system
instead which builds all automated tests in one command.


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BUILD VIA MAKEFILE

A Makefile is also provided for building the kernel, port and automated
tests. This is particularly useful for building the automated tests
because many different independent applications need to be built which is
not easily achieved within the EWSTM8 environment.

For a Windows system you can obtain a Make application suitable for use
with the IAR compiler from:

 * http://www.cosmic-software.com/comp_utils/GNU_Make.zip

Assuming you install the above into C:\Program Files\GNU_MAKE, you
should set up your environment variables as follows:

 * set PATH=%PATH%;C:\Program Files\GNU_MAKE;C:\Program Files\IAR Systems\Embedded Workbench 6.0\stm8\bin
 * set MAKE_MODE=DOS


The full build is carried out using simply:

 * make -f iar.mak

All objects are built into the 'build-iar' folder under ports/stm8. The
build process builds separate target applications for each automated test,
and appropriate .elf or .s19 files can be found in the build folder ready
for downloading to and running on the target. Because of the limited
resources on the STM8, and the large amount of automated tests, each test
is built and run as a separate application.


All built objects etc can be cleaned using:

 * make -f iar.mak clean


The Atomthreads sources are documented using Doxygen markup. You can build
both the kernel and STM8 port documentation from this folder using:

 * make -f iar.mak doxygen


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PROGRAMMING MAKEFILE-BUILT APPLICATIONS TO THE TARGET DEVICE

When developing within EWSTM8, programs can be downloaded directly to the
target. If, however, you are building applications separately using a
Makefile or similar, then you are not able to program the application
using EWSTM8. None of the tools delivered by ST appear to be designed to
cater for those who build applications externally, but it is possible using
STVP.

The following development workflow can be used (note that these settings
apply to the STM8S-Discovery):

 * Build app using Makefile.
 * Open STVP and configure to use Swim ST-Link for CPU STM8105C6.
 * Open application .s19 file and program using "Program All Tabs".

Unfortunately STVP does not have a command to reset and start the CPU
running, but it can be forced into doing so by reconfiguring the
programmer:

 * Select "Configure ST Visual Programmer" from the Configure menu.

Your application should now be programmed and running.

If you wish to program and run another application then you can open and
program it in STVP, then use the Configure menu again to reset the
device and start it running.

Other programming tools may exist but are not apparent in the toolset
delivered for use the STM8S Discovery platform.

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RUNNING THE AUTOMATED TESTS

Atomthreads contains a set of generic kernel tests which can be run on any
port to prove that all core functionality is working on your target.

The full set of tests can be found in the top-level 'tests' folder. The
Makefile builds each of these tests as independent applications in the
'build' folder. Run them individually using the STVP process described
above. For example to run the 'kern1.c' test use STVP to program and run
it.

You may also build the tests using the EWSTM8 project, but to run each
different test you must manually remove the previous test module (e.g.
kern1.c) and replace it with one of other tests, which can be quite time
consuming compared to building all tests in one command via the Makefile.

To view the test results, watch the LED on the STM8S-Discovery. This will
flash once per second if the test passed, and once every 1/8 second if the
test failed.

If you wish to use the UART, connect a serial debug cable to your target
platform (defaults to 9600bps 8N1). On starting, the test applications
print out "Go" on the UART. Once the test is complete they will print
out "Pass" or "Fail", along with other information if the test failed.

Most of the tests complete within a few seconds, but some (particularly
the stress tests) can take several seconds, so be patient. 

The full suite of tests endeavours to exercise as much of the kernel code
as possible, and can be used for quick confirmation of core OS
functionality if you ever need to make a change to the kernel or port.

The test application main() is contained in tests-main.c. This initialises
the OS, creates a main thread, and calls out to the test modules. It also
initialises the UART driver for use by stdout.


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WRITING APPLICATIONS

The easiest way to start a new application which utilises the Atomthreads
scheduler is to base your main application startup on tests-main.c. This
initialises the OS, sets up a UART and calls out to the test module entry
functions. You can generally simply replace the call to the test modules by
a call to your own application startup code.

Projects developed within EWSTM8 can be started using the sample project
atomthreads-sample-iar.ewp. If you wish to create your own EWSTM8 project
from scratch, then you should ensure you change the project settings for
both Debug and Release builds as follows:

* General Options -> Target -> Device: CPU part (e.g. "STM8S105C6")
* C/C++ Compiler -> Diagnostics: Suppress "Pa050"
* C/C++ Compiler -> Preprocessor -> Defined Symbols: 
            CPU part (e.g. "STM8S105")
            Thread stack-checking if required ("ATOM_STACK_CHECKING")
            For example "STM8S105, ATOM_STACK_CHECKING"
* Assembler -> Diagnostics: Suppress "Pa050"
* Repeat above for Debug and Release projects (you may want to 
  disable ATOM_STACK_CHECKING for Release builds).

Other options you may wish to change:

* Tools -> Options -> Editor -> EOL Characters: "Preserve". This preserves
  the line endings, bearing in mind that the Atomthreads kernels works
  with many host operating system toolchains.
* Options -> Debugger -> "ST Link" (e.g. for STM8S Discovery)

Add the .C and .S modules from the following folders:
* kernel
* ports/stm8
* ports/stm8s-periphs

Set include paths as appropriate.


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IAR COMPILER VIRTUAL REGISTERS

The STM8 has only very few CPU registers, so the IAR compiler augments
them with sixteen "virtual" registers, which are simply locations in fast
memory. These registers are called ?b0 to ?b15.

The Atomthreads context switch for IAR/STM8 takes advantage of the fact
that all CPU and most virtual registers are automatically saved on the
stack by the compiler when calling out to C functions (and even then only
if necessary). Only the virtual registers ?b8 to ?b15 are expected to be
preserved by called functions, so these are the only registers that
callers to the context switch routine will not automatically save if
necessary.

For cooperative context switches (where a thread calls an OS kernel
function to schedule itself out), most registers will therefore already
be saved on a thread's stack if necessary. Only ?b8 to ?b15 actually have
to be saved in the context switch routine, making cooperative switches
potentially very cheap if few registers must be preserved.

For preemptive switches (where an ISR has interrupted a thread and wishes
to switch to a new thread), the interrupt handler prologue automatically
saves all CPU registers (actually done automatically by the CPU) and the
virtual registers ?b0 to ?b7. Still only the registers ?b8 to ?b15 have to
be saved by the context-switch routine, but in this case ?b0 to ?b7 and the
CPU registers are always saved on the thread's stack by the ISR prologue.
This is because the ISR has no knowledge of what registers the interrupted
thread was using, so we cannot take advantage of the potential for saving
fewer than the full set of registers that we achieve with cooperative
switches.


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