User scripts

Introduction

pyOCD has support for customization through what are called user scripts. These are Python scripts that are loaded by pyOCD before it connects to the target. A user script can define functions that are called as hooks at certain points in the connection lifetime, and can extend, modify, or completely override the default behaviour.

If a file named pyocd_user.py or .pyocd_user.py is placed in the project directory, pyOCD will automatically detect it and load it as a user script. If you prefer another name, you can set the user_script session option, for example in a config file, or by passing the --script=<path> command line argument. If a relative path is set either with the option or command line, it will be searched for in the project directory.

Examples

This example user script shows how to add a new memory region.

# This example applies to the Nordic nRF52 devices.

def will_connect(board):
    # Create the new ROM region for the FICR.
    ficr = RomRegion(
                name="ficr",
                start=0x10000000,
                length=0x460
                )

    # Add the FICR region to the memory map.
    target.memory_map.add_region(ficr)

This example shows how to override the flash algorithm for an external flash memory.

# This example applies to the NXP i.MX RT10x0 devices.

# Unlike the previous example, the board argument is excluded here.
def will_connect():
    # Look up the external flash memory region.
    extFlash = target.memory_map.get_first_matching_region(name="flexspi")

    # Set the path to an .FLM flash algorithm.
    extFlash.flm = "MIMXRT105x_QuadSPI_4KB_SEC.FLM"

This example demonstrates setting the DBGMCU_CR register after connecting for STM32 devices.

# This example applies to the ST STM32L0x1 devicess.

DBG_CR = 0x40015804

def did_connect():
    # Set STANDBY, STOP, and SLEEP bits all to 1.
    target.write32(DBG_CR, 0x7)

Another common use for a script is to initialize external memory such as SDRAM.

User-defined commands

New commands accessible from the commander subcommand or gdbserver monitor commands can be easily created in a user script.

User defined commands are created by using the @command() decorator on a function. The name of the new command can either be the same as the name of the decorated function, or can be set explicitly with a name (or first positional) argument to the decorator. For instance, either @command('mycmd') or @command(name='anothercmd'). Note that the decorator requires parentheses (it must be called as a function) even if there are no parameters.

Parameters for the new command are automatically determined using introspection and type annotations. Arguments for parameters of these types are converted to the appropriate type before the function is called as a command.

Supported parameter types:

  • int
  • float
  • str
  • Variable arguments, e.g. *args.

Keyword parameters are not allowed.

An int parameter is converted using the same method as for other pyOCD commands. Hexadecimal and binary numbers are allowed, digits can be separated by underscores, and so on. For variable arguments, type annotations are ignored and the tuple passed to the function will contain strings as entered in the command invocation.

The decorated function remains accessible as a regular function in the user script namespace, and is therefore callable from other functions within the user script. This is true even if the function definition is not compatible with the command decorator, for instance if it has invalid parameter types.

Help for the new command can be specified by passing a help argument to the @command decorator.

Example:

@command(help="Decode and print the first few vectors")
def vectable(base: int):
    vecs = target.read_memory_block32(base, 4)
    print(f"Initial SP:     {vecs[0]:#010x}")
    print(f"ResetHandler:   {vecs[1]:#010x}")
    print(f"NMI:            {vecs[2]:#010x}")
    print(f"HardFault:      {vecs[3]:#010x}")

Script globals

A number of useful symbols are made available in the global namespace of user scripts. These include both target related objects, as well as parts of the pyOCD Python API.

The usual Python builtins are available.

Objects and functions

Symbol Description
aps Dictionary of CoreSight Access Port (AP) objects. The keys are the APSEL value.
board The Board object.
command Decorator for defining new commands. See user-defined commands for details.
debug Log a debug message.
dp The CoreSight Debug Port (DP) object.
error Output an error log.
info Output an info-level log message.
LOG Logger object for the user script.
options The session options dictionary.
probe The connected debug probe object.
session The session object, which is the root of the connection object graph.
target The CoreSightTarget or subclass instance representing the MCU.
warning Log a warning.

Modules and classes

Symbol Description
BreakpointType Enumeration of breakpoint types.
DeviceRegion Device-type memory region class.
Error The base class for all pyOCD exceptions.
Event Enumeration of notification event types.
exceptions Module containing the exception classes.
FileProgrammer Utility class to program files to target flash.
FlashEraser Utility class to erase target flash.
FlashLoader Utility class to program raw binary data to target memory. Deprecated, use MemoryLoader instead.
FlashRegion Flash memory region.
HaltReason Enumeration of halt reasons.
MemoryLoader Utility class to program raw binary data to target memory.
MemoryMap Class representing the device’s memory map.
MemoryType Memory region type enumeration.
pyocd The root pyOCD module.
RamRegion RAM memory region.
ResetType Reset type enumeration.
RomRegion ROM memory region.
RunType Enumeration of types of run operations (step or run).
SecurityState Enumeration of core security states.
State Enumeration of target state.
Target Base target class.
TransferError Exception class for all transfer errors.
TransferFaultError Exception subclass of TransferError for memory transfer faults.
VectorCatch Namespace class containing bit mask constants for vector catch options.
WatchpointType Enumeration of watchpoint types.

Delegate functions

This section documents all functions that user scripts can provide to modify pyOCD’s behaviour. Some are simply notifications, while others allow for overriding of default behaviour. Collectively, these are called delegate functions.

All parameters of user script delegate functions are optional. Parameters can be declared in any order, and those that are not needed can be excluded. In fact, most parameters are not necessary because the same objects are available as script globals, for instance session and target.

Those parameters that are present must have names matching the specification below, and there must not be additional unspecified, required parameters (those without a default value). Extra optional parameters are allowed but will never be passed any value other than the default, unless you call the function yourself from within the script.

will_connect

Pre-init notification for the board.

will_connect(board: Board) -> None

Parameters
board - A Board instance that is about to be initialized.
Result
Ignored.

did_connect

Post-initialization notification for the board.

did_connect(board: Board) -> None

Parameters
board - A Board instance.
Result
Ignored.

will_init_target

Hook to review and modify init call sequence prior to execution.

will_init_target(target: SoCTarget, init_sequence: CallSequence) -> None

Parameters
target - An SoCTarget object about to be initialized.
init_sequence - The CallSequence that will be invoked. Because call sequences are mutable, this parameter can be modified before return to change the init calls.
Result
Ignored.

did_init_target

Post-initialization notification.

did_init_target(target: SoCTarget) -> None

Parameters
target - An SoCTarget object.
Result
Ignored.

will_start_debug_core

Notification hook for before core debug is enabled.

will_start_debug_core(core: CoreTarget) -> None

Parameters
core - A CoreTarget object about to be initialized.
Result
Ignored.

This hook is called during connection, prior to any register accesses being performed on the indicated core (aside from the CoreSight peripheral ID registers that were read to identify the core’s presence during discovery).

start_debug_core

Hook to enable debug for the given core.

start_debug_core(core: CoreTarget) -> Optional[bool]

Parameters
core - A CoreTarget object about to be initialized.
Result
True Do not perform the normal procedure to start core debug.
False/None Continue with normal behaviour.

did_start_debug_core

Notification hook that core debug has been enabled.

did_start_debug_core(core: CoreTarget) -> None

Parameters
core - A CoreTarget object.
Result
Ignored.

This hook method is called once a debug has been enabled for a core, and it has been fully identified.

will_stop_debug_core

Pre core disconnect notification hook for the core.

will_stop_debug_core(core: CoreTarget) -> None

Parameters
core - A CoreTarget object.
Result
Ignored.

stop_debug_core

Core debug disable hook.

stop_debug_core(core: CoreTarget) -> Optional[bool]

Parameters
core - A CoreTarget object.
Result
True Do not perform the normal procedure to disable core debug.
False/None Continue with normal behaviour.

did_stop_debug_core

Post core disconnect notification hook for the core.

did_stop_debug_core(core: CoreTarget) -> None

Parameters
core - A CoreTarget object.
Result
Ignored.

will_disconnect

Pre-disconnect notification.

will_disconnect(target: SoCTarget, resume: bool) -> None

Parameters
target - An SoCTarget object.
resume - The value of the disconnect_on_resume option.
Result
Ignored.

did_disconnect

Post-disconnect notification.

did_disconnect(target: SoCTarget, resume: bool) -> None

Parameters
target - An SoCTarget object.
resume - The value of the disconnect_on_resume option.
Result
Ignored.

will_reset

will_reset(core: CoreTarget, reset_type: Target.ResetType) -> Optional[bool]

Pre-reset hook.

Parameters
core - A CoreTarget instance.
reset_type - One of the Target.ResetType enumerations.
Result
True The hook performed the reset.
False/None Caller should perform the normal reset procedure.

did_reset

Post-reset notification.

did_reset(core: CoreTarget, reset_type: Target.ResetType) -> None

Parameters
core - A CoreTarget instance.
reset_type - One of the Target.ResetType enumerations.
Result
Ignored.

set_reset_catch

Hook to prepare target for halting on reset.

set_reset_catch(core: CoreTarget, reset_type: Target.ResetType) -> Optional[bool]

Parameters
core - A CoreTarget instance.
reset_type - One of the Target.ResetType enumerations.
Result
True This hook handled setting up reset catch, caller should do nothing.
False/None Perform the default reset catch set using vector catch.

clear_reset_catch

Hook to clean up target after a reset and halt.

clear_reset_catch(core: CoreTarget, reset_type: Target.ResetType) -> None

Parameters
core - A CoreTarget instance.
reset_type - One of the Target.ResetType enumerations.
Result
Ignored.

mass_erase

Hook to override mass erase.

mass_erase(target: SoCTarget) -> Optional[bool]

Parameters
target - An SoCTarget object.
Result
True Indicate that mass erase was performed by the hook.
False/None Mass erase was not overridden and the caller should proceed with the standard mass erase procedure.

trace_start

Notification to prepare for tracing the target.

trace_start(target: SoCTarget, mode: int) -> None

Parameters
target - A CoreSightTarget object.
mode - The trace mode. Currently always 0 to indicate SWO.
Result - Ignored.

trace_stop

Notification to clean up after tracing the target.

trace_stop(target: SoCTarget, mode: int) -> None

Parameters
target - A CoreSightTarget object.
mode - The trace mode. Currently always 0 to indicate SWO.
Result
Ignored.