### Command: start JSON example

Source: https://syntalos.org/docs/network-ctl-protocol

Example of the `start` command broadcast after the controller has received all required `prepare` ACKs and has started its own master timer. The `ts_start_us` field is the controller wall-clock start in microseconds since Unix epoch.

```json
{
  "v": 1,
  "type": "start",
  "sender": "rig-ctrl",
  "run_id": "019312ab-...",
  "ts_start_us": 1737000000123456
}
```

--------------------------------

### Install Syntalos on Ubuntu: add repository, apt install, dialout group

Source: https://syntalos.org/get

Set up the APT repository for Syntalos on Ubuntu, install the package, and grant the current user access to serial devices. Run the setup command first; it adds an APT source. Then install with apt and add the user to the dialout group.

```bash
curl -fsSL https://syntalos.org/setup/setup-syntalos-repo.sh | sudo sh
```

```bash
sudo apt install syntalos
```

```bash
sudo usermod -a -G dialout $USER
```

--------------------------------

### Command: prepare JSON example

Source: https://syntalos.org/docs/network-ctl-protocol

Example of the `prepare` command broadcast by the controller before a run starts. Listeners should apply the provided parameters and prepare the run.

```json
{
  "v": 1,
  "type": "prepare",
  "sender": "rig-ctrl",
  "run_id": "019312ab-...",
  "project": "my-project",
  "subject_id": "M42",
  "subject_group": "control",
  "experiment_id": "novel-object-1"
}
```

--------------------------------

### virtual void start()

Source: https://syntalos.org/api/files/moduleapi_8h

Starts the module execution.

```APIDOC
## virtual void start()

### Description
Starts the module execution.

### Method
start()
```

--------------------------------

### start()

Source: https://syntalos.org/api/classes/classsyntalos_1_1mlinkmodule

Starts the experiment run.

```APIDOC
## virtual void start() override

### Description
Run when the experiment is started and the HRTimer has an initial time set. Switches the module into “Started” mode.
```

--------------------------------

### MLinkModule Start Method

Source: https://syntalos.org/api/files/mlinkmodule_8cpp

Initializes the module start process, updates input port metadata, and launches the module.

```cpp
void MLinkModule::start()
{
    d->portChangesAllowed = false;

    // timestamp when this module was started
    auto startTimestampUs = std::chrono::duration_cast<std::chrono::microseconds>(
                                m_syTimer->currentTimePoint().time_since_epoch())
                                .count();

    // update input port metadata if the metadata has changed - this may happen in case of circular module connections
    for (auto &iport : inPorts()) {
        if (!iport->hasSubscription())
            continue;

        const auto mdata = iport->subscriptionVar()->metadata();
        const auto portId = iport->id().toStdString();
        if (d->sentMetadata.value(portId, MetaStringMap()) == mdata)
            continue;

        UpdateInputPortMetadataRequest req;
        req.id = portId;
        req.metadata = mdata;
        if (!d->callSliceClientSimple(
                this,
                IN_PORT_UPDATE_METADATA_ID,
                req,
                5,
                IpcCallFlag::TimeoutIsError | IpcCallFlag::SkipWaitOnError))
            return;
    }
    d->sentMetadata.clear();

    // tell the module to launch!
    d->callClientSimple<StartRequest>(
        this,
        START_CALL_ID,
        [&](auto &req) {
            req.startTimestampUsec = startTimestampUs;
        },
        2);

    // stop reading control events in the GUI thread - the module thread will do that for us soon
    d->ctlEventTimer->stop();

    // Start all output streams, regardless of whether they have a master-side IPC
    // forwarder. This re-snapshots the (now-final and immutable) metadata into all
    // output-port subscriptions, including pure MLink->MLink ports that have no
    // forwarder entry in outPortSubs. Destination MLink workers read metadata from
    // the in-process subscription via UpdateInputPortMetadataRequest and need it set.
    for (auto &oport : outPorts()) {
        if (oport->streamVar()->hasSubscribers())
            oport->startStream();
    }

    // call generic
    AbstractModule::start();
}
```

--------------------------------

### start

Source: https://syntalos.org/api/classes/classsyntalos_1_1secondaryclocksynchronizer

Starts the synchronizer.

```APIDOC
## start

### Description
Starts the synchronizer.

### Method
bool start()

### Parameters
None.

### Request Example
```cpp
bool start();
```

### Response
- **Return Value** (bool) - True if start succeeded, false otherwise.
```

--------------------------------

### start()

Source: https://syntalos.org/api/classes/classsyntalos_1_1synctimer

Starts the timer.

```APIDOC
## start()

### Description
Starts the timer.

### Method
Member function

### Signature
```cpp
void start()
```

### Parameters
None.

### Returns
void

```

--------------------------------

### Install and run Syntalos on Windows via WSL2

Source: https://syntalos.org/docs/setup/install-windows

Commands to install and run Syntalos on Windows via WSL2. The first block adds the Flatpak PPA, updates the system, and installs Flatpak and xdg-desktop-portal-kde. The second block adds the Flathub remote and installs Syntalos, requiring two Enter confirmations. The third block creates a symlink so Syntalos appears in Windows menus. The fourth block launches Syntalos from the WSL command line.

```bash
sudo add-apt-repository --yes ppa:flatpak/stable
sudo apt update && sudo apt -y full-upgrade && sudo apt --purge -y autoremove
sudo apt install -y flatpak xdg-desktop-portal-kde
```

```bash
sudo flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
sudo flatpak install org.syntalos.syntalos
```

```bash
sudo mkdir -p /usr/local/share/applications/
sudo ln -s /var/lib/flatpak/exports/share/applications/org.syntalos.syntalos.desktop /usr/local/share/applications/
```

```bash
flatpak run org.syntalos.syntalos
```

--------------------------------

### Create Python Virtual Environment

Source: https://syntalos.org/api/files/pyvenvmanager_8cpp

Initializes a new virtual environment, handling directory creation and temporary file setup for installation commands.

```cpp
auto createPythonVirtualEnv(const QString &venvName, const QString &requirementsFile, bool recreate)
    -> std::expected<QString, QString>
{
    auto rtdDir = QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation);
    if (rtdDir.isEmpty())
        rtdDir = "/tmp";
    const auto venvDir = pythonVEnvDirForName(venvName);

    if (QDir(venvDir).exists()) {
        if (recreate) {
            LOG_INFO(logVEnv, "Removing existing virtualenv before recreation: {}", venvDir);
            if (!QDir(venvDir).removeRecursively())
                return std::unexpected(QStringLiteral("Unable to remove existing virtualenv: %1").arg(venvDir));
        } else {
            // nothing to do, the venv already exists
            return venvDir;
        }
    }

    QDir().mkpath(venvDir);

    const auto tmpCommandFile = QStringLiteral("%1/sy-venv-%2.sh").arg(rtdDir, createRandomString(6));
    QFile shFile(tmpCommandFile);
    if (!shFile.open(QIODevice::WriteOnly | QIODevice::Text)) {
        LOG_WARNING(logVEnv, "Unable to open temporary file {} for writing.", tmpCommandFile);
        return std::unexpected(
            QStringLiteral("Unable to open temporary file for virtualenv creation: %1").arg(shFile.errorString()));
    }

    const auto tmpRequirementsFname = QStringLiteral("%1/%2-requirements_%3.txt")
                                          .arg(rtdDir, venvName, createRandomString(4));
    QFile tmpReqFile(tmpRequirementsFname);
    if (!tmpReqFile.open(QIODevice::WriteOnly | QIODevice::Text)) {
        LOG_WARNING(logVEnv, "Unable to open temporary file {} for writing.", tmpRequirementsFname);
        return std::unexpected(
            QStringLiteral("Unable to open temporary file for virtualenv creation: %1").arg(tmpReqFile.errorString()));
    }
```

--------------------------------

### start

Source: https://syntalos.org/api/classes/classsyntalos_1_1mlinkmodule

Starts the module when the experiment is started.

```APIDOC
## start

### Description
Run when the experiment is started and the HRTimer has an initial time set. Switches the module into "Started" mode.

### Signature
virtual void start() override
```

--------------------------------

### Install Syntalos via APT

Source: https://syntalos.org/docs/setup/install

Install the Syntalos package using the APT package manager after setting up the repository.

```bash
sudo apt install syntalos
```

--------------------------------

### Install Syntalos via Flatpak

Source: https://syntalos.org/docs/setup/install

Commands to install Flatpak, add the Flathub remote, and install the Syntalos Flatpak bundle.

```bash
# replace this command with the distribution's native package manager to install Flatpak
sudo apt install flatpak
# set up Flathub
sudo flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
# install Syntalos
flatpak install flathub org.syntalos.syntalos
```

--------------------------------

### start()

Source: https://syntalos.org/api/classes/classdatastream

Starts the data stream, allowing data to be pushed and received.

```APIDOC
## start()

### Description
Starts the data stream, allowing data to be pushed and received.

### Method
virtual void start() override

```

--------------------------------

### MLinkModule constructor with QProcess setup

Source: https://syntalos.org/api/files/mlinkmodule_8cpp

Constructor for MLinkModule. Sets up the QProcess, enables persistent worker mode, allows port changes, captures output, connects process signals, and starts a control event timer.

```cpp
MLinkModule::MLinkModule(QObject *parent)
    : AbstractModule(parent),
      d(new MLinkModule::Private(m_log))
{
    d->proc = new QProcess(this);
    d->workerMode = ModuleWorkerMode::PERSISTENT;
    d->portChangesAllowed = true;

    // merge stdout/stderr of external process with ours by default
    setOutputCaptured(false);

    connect(d->proc, &QProcess::readyReadStandardOutput, this, [this]() {
        if (d->outputCaptured)
            Q_EMIT processOutputReceived(ChannelStdout, readProcessOutput(ChannelStdout));
    });
    connect(d->proc, &QProcess::readyReadStandardError, this, [this]() {
        if (d->outputCaptured)
            Q_EMIT processOutputReceived(ChannelStderr, readProcessOutput(ChannelStderr));
    });
    connect(
        d->proc,
        static_cast<void (QProcess::*)(int, QProcess::ExitStatus)>(&QProcess::finished),
        this,
        [this](int exitCode, QProcess::ExitStatus exitStatus) {
            if (exitStatus == QProcess::CrashExit) {
                raiseError(QStringLiteral("Module process crashed with exit code %1! Check the log for details.")
                               .arg(exitCode));
            }
        });

    d->ctlEventTimer = new QTimer(this);
    d->ctlEventTimer->setInterval(100);
    connect(d->ctlEventTimer, &QTimer::timeout, this, [this]() {
        handleIncomingControl();
    });
}
```

--------------------------------

### Implement periodic control commands

Source: https://syntalos.org/tutorials/03_script-control

A complete script example that sends a 2-second start command to a module every 5 seconds. It uses ControlCommand to define the action and schedule_delayed_call for non-blocking timing.

```python
import syntalos_mlink as syl


oport = syl.get_output_port('control-out')


def start():
    """Called by Syntalos immediately when the experiment is started."""
    send_beep()


def send_beep():
    ctl = syl.ControlCommand()
    ctl.kind = syl.ControlCommandKind.START
    ctl.duration = 2000  # run for 2 sec
    oport.submit(ctl)

    if not syl.is_running():
        return

    # run again in 5 sec
    syl.schedule_delayed_call(5 * 1000, send_beep)
```

--------------------------------

### Install syntalos-hwsupport on Debian/Ubuntu

Source: https://syntalos.org/docs/setup/hardware-support

Use this command to manually install the downloaded hardware support package on Debian or Ubuntu systems.

```bash
sudo apt install ./syntalos-hwsupport_*_all.deb
```

--------------------------------

### using StartFn

Source: https://syntalos.org/api/namespaces/namespacesyntalos

Function type for starting a process.

```cpp
using Syntalos::StartFn = typedef std::function<void()>;
```

--------------------------------

### start

Source: https://syntalos.org/api/classes/classdatastream

Starts the stream.

```APIDOC
## start()

### Description
Starts the stream. Overrides VariantDataStream::start.

### Signature
```cpp
inline virtual void start() override
```
```

--------------------------------

### Install CI dependencies for Debian/Ubuntu

Source: https://syntalos.org/docs/setup/install

Run the CI system's dependency installation script to install all required packages on Debian or Ubuntu. The script uses APT with fsync/sync disabled for speed, which may risk data corruption during power outages; install packages manually if concerned.

```bash
sudo ./tests/ci/install-deps-deb.sh
```

--------------------------------

### runProcess()

Source: https://syntalos.org/api/classes/classsyntalos_1_1mlinkmodule

Starts the process.

```APIDOC
## bool runProcess()

### Description
Starts the process.

### Returns
bool - True if the process started successfully, false otherwise.
```

--------------------------------

### Install Syntalos package on Debian/Ubuntu

Source: https://syntalos.org/docs/setup/install

Install the Syntalos .deb package using apt. Requires Debian 13 (Trixie) or later, or Ubuntu 24.04 (Noble Numbat) or later. After installation, launch Syntalos from the application menu or command line.

```bash
sudo apt install ./syntalos_*.deb
```

--------------------------------

### startWallTime() const

Source: https://syntalos.org/api/classes/classsyntalos_1_1synctimer

Returns the wall-clock time at which the timer was started (system_clock). Captured atomically alongside the master clock in start() / startAt(), so it can be used as an absolute reference for cross-device alignment.

```APIDOC
## startWallTime() const

### Description
Returns the wall-clock time at which the timer was started (system_clock). Captured atomically alongside the master clock in start() / startAt(), so it can be used as an absolute reference for cross-device alignment.

### Method
Member function

### Signature
```cpp
inline std::chrono::system_clock::time_point startWallTime() const
```

### Parameters
None.

### Returns
std::chrono::system_clock::time_point - The wall-clock start time.

```

--------------------------------

### SyntalosLink constructor: enable async start and set INITIALIZING state

Source: https://syntalos.org/api/files/syntaloslink_8cpp

Sets the module to use asynchronous start and immediately signals initialization. A client using this interface must set the state to IDLE after setting up its basics.

```cpp
    // we us the fast, async start() by default
    d->allowAsyncStart = true;

    // Immediately upon creation, we send a message that we are initializing.
    // A client using this interface has to set this to IDLE once it has set up the basics.
    setState(ModuleState::INITIALIZING);
}
```

--------------------------------

### Syntalos link service request loops (UpdateInputPortMetadata, SaveSettings, LoadSettings, PrepareRun, Start)

Source: https://syntalos.org/api/files/syntaloslink_8cpp

Handles the main service request loops for a Syntalos link module: updating input-port metadata, saving/loading settings, preparing a run, and starting the run. Each loop receives a request, processes it, and replies with success or failure; failures log an error and break the loop. The PrepareRun handler builds a local EDL tree root and sets the module state to PREPARING then READY on success, while Start creates a SyncTimer and flushes output-port publishers.

```cpp
        // we will have to rebuild the waitset after ports changed
        d->waitSetDirty = true;
    }

    // ---- UpdateInputPortMetadata ----
    while (true) {
        auto req = safeReceive(*d->srvUpdateIPortMetadata);
        if (!req.has_value())
            break;
        const auto pl = req->payload();
        const auto reqUpdateMD = UpdateInputPortMetadataRequest::fromMemory(pl.data(), pl.number_of_bytes());

        // update metadata
        for (const auto &ip : d->inPortInfo) {
            if (ip->id() == reqUpdateMD.id) {
                ip->d->metadata = reqUpdateMD.metadata;
                break;
            }
        }

        Private::replyDoneSlice(*req, true);
    }

    // ---- SaveSettings ----
    while (true) {
        auto req = safeReceive(*d->srvSaveSettings);
        if (!req.has_value())
            break;
        const auto pl = req->payload();
        const auto ssReq = SaveSettingsRequest::fromMemory(pl.data(), pl.number_of_bytes());
        SaveSettingsResponse ssResp;
        ssResp.success = true;
        if (d->saveSettingsCb)
            ssResp.success = d->saveSettingsCb(ssResp.data, ssReq.baseDir);

        auto ssRespData = ssResp.toBytes();
        auto maybeResponse = req->loan_slice_uninit(ssRespData.size());
        if (!maybeResponse.has_value()) {
            SY_LOG_ERROR(
                logSyLink,
                "Failed to loan response ({} bytes) for reply to SaveSettings: {}",
                ssRespData.size(),
                iox2::bb::into<const char *>(maybeResponse.error()));
            break;
        }

        auto rawResponse = std::move(maybeResponse).value();
        std::memcpy(rawResponse.payload_mut().data(), ssRespData.data(), ssRespData.size());
        iox2::send(iox2::assume_init(std::move(rawResponse))).value();
    }

    // ---- LoadSettings ----
    while (true) {
        auto req = safeReceive(*d->srvLoadSettings);
        if (!req.has_value())
            break;
        const auto pl = req->payload();
        const auto lsReq = LoadSettingsRequest::fromMemory(pl.data(), pl.number_of_bytes());
        auto success = true;
        if (d->loadSettingsCb)
            success = d->loadSettingsCb(lsReq.data, lsReq.baseDir);

        Private::replyDoneSlice(*req, success);
    }

    // ---- PrepareRun ----
    while (true) {
        auto req = safeReceive(*d->srvPrepareRun);
        if (!req.has_value())
            break;
        const auto pl = req->payload();
        const auto prepReq = PrepareRunRequest::fromMemory(pl.data(), pl.number_of_bytes());

        // set up run info and build local EDL tree root
        d->runInfo = LinkRunInfo{};
        d->runInfo.uuid = Uuid(prepReq.runUuid);
        d->runInfo.subject.id = prepReq.subjectId;
        d->runInfo.subject.group = prepReq.subjectGroup;
        d->runInfo.experimentId = prepReq.experimentId;
        d->runInfo.isEphemeral = prepReq.isEphemeral;
        d->runInfo.moduleName = prepReq.moduleName;
        if (!prepReq.edlRootPath.empty()) {
            const fs::path rootPath(prepReq.edlRootPath);
            auto rootGroup = std::make_shared<EDLGroup>(rootPath.filename().string());
            rootGroup->setPath(rootPath);
            rootGroup->setCollectionId(prepReq.runUuid);
            d->runInfo.rootGroup = std::move(rootGroup);
        }

        // prepare the run
        setState(ModuleState::PREPARING);
        auto success = true;
        if (d->prepareRunCb)
            success = d->prepareRunCb();

        Private::replyDoneSlice(*req, success);
        if (success)
            setState(ModuleState::READY);
    }

    // ---- Start ----
    while (true) {
        auto req = safeReceive(*d->srvStart);
        if (!req.has_value())
            break;

        const auto timePoint = symaster_timepoint(microseconds_t(req->payload().startTimestampUsec));
        d->syTimer = std::make_shared<SyncTimer>();
        d->syTimer->startAt(timePoint);

        // Ensure all output-port publishers know about subscribers that connected
        // during the prepare phase.
        for (auto &oport : d->outPortInfo) {
            if (oport->d->ioxPub.has_value())
                oport->d->ioxPub->handleEvents();
        }

```

--------------------------------

### startStream()

Source: https://syntalos.org/api/classes/classsyntalos_1_1streamoutputport

Starts the data stream for this output port.

```APIDOC
## startStream()

### Description
Starts the data stream for this output port.

```

--------------------------------

### SimpleTerminal::startShell

Source: https://syntalos.org/api/classes/classsyntalos_1_1simpleterminal

Starts the configured shell program in the terminal.

```APIDOC
## SimpleTerminal::startShell

### Description
Start the shell program.

### Signature
```cpp
void startShell()
```
```

--------------------------------

### Set up Syntalos APT repository

Source: https://syntalos.org/docs/setup/install

Run this command in a terminal to add the Syntalos software source to your Debian or Ubuntu system.

```bash
curl -fsSL https://syntalos.org/setup/setup-syntalos-repo.sh | sudo sh
```

--------------------------------

### ACK message JSON example

Source: https://syntalos.org/docs/network-ctl-protocol

Example of an ACK message sent by a listener on the PUSH socket. The `ack_for` field indicates the phase being acknowledged (`prepare`, `start`, or `stop`).

```json
{
  "v": 1,
  "type": "ack",
  "sender": "rig-cam",
  "run_id": "019312ab-...",
  "ack_for": "prepare",
  "success": true
}
```

--------------------------------

### Boilerplate Python script for Firmata control

Source: https://syntalos.org/tutorials/04_firmata-interface

Initial Python module code that imports syntalos_mlink, gets input/output ports (firmata-in, firmatactl-out, table-out), and defines prepare(), start(), stop() functions. This does nothing yet but sets up the structure for later automation.

```python
import syntalos_mlink as syl


fm_iport = syl.get_input_port('firmata-in')
fm_oport = syl.get_output_port('firmatactl-out')
tab_oport = syl.get_output_port('table-out')


def prepare() -> bool:
    """This function is called before a run is started.
    You can use it for (slow) initializations."""
    return True


def start():
    """This function is called immediately when a run is started.
    This function should complete extremely quickly."""
    pass


def stop():
    """This function is called once a run is stopped."""
    pass

```

--------------------------------

### MLinkModule::runProcess

Source: https://syntalos.org/api/files/mlinkmodule_8cpp

Initializes and starts the module process, sets up the environment, and waits for the worker to signal readiness.

```cpp
bool MLinkModule::runProcess()
{
    // ensure any existing process does not exist
    terminateProcess();

    // reset connection, just in case we changed our ID
    try {
        resetConnection();
    } catch (const std::exception &e) {
        raiseError(QStringLiteral("Failed to set up module IPC connection: %1").arg(e.what()));
        return false;
    }

    if (d->proc->program().isEmpty()) {
        LOG_ERROR(m_log, "MLink module has not set a worker binary");
        return false;
    }

    auto penv = moduleBinaryEnv();
    penv.insert("SYNTALOS_VERSION", syntalosVersionFull());
    penv.insert("SYNTALOS_MODULE_ID", d->clientId.c_str());
    if (!d->pyVenvDir.isEmpty()) {
        penv.remove("PYTHONHOME");
        penv.insert("VIRTUAL_ENV", d->pyVenvDir);
        penv.insert("PATH", QStringLiteral("%1/bin/:%2").arg(d->pyVenvDir, penv.value("PATH", "")));
    }

    // When launching the external process, we are back at initialization
    // If we are in an error state, we clear it and return to IDLE after a restart.
    auto prevState = (state() == ModuleState::ERROR) ? ModuleState::IDLE : state();
    setState(ModuleState::INITIALIZING);

    d->proc->setProcessEnvironment(penv);
    d->proc->start(d->proc->program(), d->proc->arguments());
    if (!d->proc->waitForStarted())
        return false;

    // wait for the service to show up & initialize
    bool workerFound = false;
    bool moduleInitDone = false;
    QElapsedTimer timer;
    timer.start();
    do {
        handleIncomingControl();

        if (!workerFound && state() != prevState)
            workerFound = true;
        if (state() == ModuleState::IDLE)
            moduleInitDone = true;

        if (!workerFound || !moduleInitDone)
            std::this_thread::sleep_for(microseconds_t(1500));

        if (timer.elapsed() > 10 * 1000)
            break;
    } while (!workerFound || !moduleInitDone);

    if (!workerFound) {
        raiseError(
            "Module communication interface did not show up in time! The module might have crashed or may not be "
            "configured correctly.");
        d->proc->kill();
        return false;
    }

    if (!moduleInitDone) {
        raiseError("Module initialization failed! The module might have failed or was taking too long to initialize.");
        d->proc->kill();
        return false;
    }

    // verify IPC/API compatibility before issuing further control commands
    if (!testIpcApiVersion(true)) {
        d->proc->terminate();
        return false;
    }

    if (state() != ModuleState::ERROR)
        setState(prevState);

    // send settings to the worker, if we have any (might be the case if we are trying
    // to resurrect a crashed worker)
    sendSettings();

    // Keep control events flowing while the worker is alive and no module run thread is active.
    d->ctlEventTimer->start();

    return true;
}
```

--------------------------------

### Prepare MLinkModule Process

Source: https://syntalos.org/api/files/mlinkmodule_8cpp

Initializes the module process, verifies communication, sets process niceness and realtime priority, and loads necessary scripts.

```cpp
bool MLinkModule::prepare(const RunInfo &info)
{
    // ensure we are reading any messages from the module process
    d->ctlEventTimer->start();

    // at this point, ensure the module process is actually running
    if (!isProcessRunning()) {
        if (!runProcess())
            return false;
    }

    // use version check as a "ping" to see if the worker is alive
    if (!testIpcApiVersion(false)) {
        raiseError("Failed to communicate with module process! Version check failed.");
        return false;
    }

    // set module process niceness
    if (!d->callClientSimple<SetNicenessRequest>(this, SET_NICENESS_CALL_ID, [&](auto &req) {
            req.nice = defaultThreadNiceness();
        }))
        return false;

    // set module process realtime priority, but only if the engine approved this
    // module for realtime scheduling within the shared RtKit budget (otherwise the
    // worker would self-elevate past the limit). A priority of 0 disables realtime.
    if (!d->callClientSimple<SetMaxRealtimePriority>(this, SET_MAX_RT_PRIORITY_CALL_ID, [&](auto &req) {
            req.priority = isRealtimeApproved() ? defaultRealtimePriority() : 0;
        }))
        return false;

    // send all port information to the module (sets topology / metadata on worker side)
    if (!sendPortInformation())
        return false;

    // set the script to be run, if any exists and we are using a transient worker
    // (for persistent workers, the script has already been loaded in initialize())
    // resetPorts is NOT requested here: the worker keeps the ports that sendPortInformation()
    // just provided so the script can call get_input_port() / get_output_port() at module level.
    if (d->workerMode == ModuleWorkerMode::TRANSIENT) {
        if (!loadCurrentScript(false))
            return false;
    }

    // ensure we use the latest settings data received from the worker
    handleIncomingControl();
```

--------------------------------

### virtual bool loadSettings(const QString &confBaseDir, const QVariantHash &settings, const QByteArray &extraData)

Source: https://syntalos.org/api/files/moduleapi_8h

Loads module settings from the provided containers. Returns true on success.

```APIDOC
## virtual bool loadSettings(const QString &confBaseDir, const QVariantHash &settings, const QByteArray &extraData)

### Description
Loads module settings from the provided containers. Returns true on success.

### Method
loadSettings(const QString &confBaseDir, const QVariantHash &settings, const QByteArray &extraData)

### Parameters
- **confBaseDir** (QString) - Required - The base directory for configuration files.
- **settings** (QVariantHash&) - Required - The settings hash to load from.
- **extraData** (QByteArray&) - Required - The extra data buffer to load from.

### Returns
bool - True if loading succeeded, false otherwise.
```

--------------------------------

### allow_async_start: bool

Source: https://syntalos.org/docs/pysy-mlink-api

Whether start() is run in parallel with other modules for this module. On startup, Syntalos can send START to all external modules in parallel, not waiting for them to finish individual START actions. This is the async-start method, and it results in much better aligned start times of modules. However, some modules may need to modify stream metadata in START and must ensure it is received before their streams are started. Those modules may want to disable async-start for themselves, so they run exclusively and the engine waits for them to complete START actions.

```APIDOC
## allow_async_start: bool

### Description
Whether start() is run in parallel with other modules for this module. On startup, Syntalos can send START to all external modules in parallel, not waiting for them to finish individual START actions. This is the async-start method, and it results in much better aligned start times of modules. However, some modules may need to modify stream metadata in START and must ensure it is received before their streams are started. Those modules may want to disable async-start for themselves, so they run exclusively and the engine waits for them to complete START actions.

### Type
- **bool** - Boolean flag.
```

--------------------------------

### MLinkModule Run Preparation

Source: https://syntalos.org/api/files/mlinkmodule_8cpp

Handles the module's startup preparations, including sending a prepare run request and waiting for the module to reach the READY state.

```cpp
// call the module's own startup preparations
    const auto sg = storageGroup();
    PrepareRunRequest prepReq{
        .runUuid = info.uuid,
        .subjectId = info.subject.id.toStdString(),
        .subjectGroup = info.subject.group.toStdString(),
        .experimentId = info.experimentId.toStdString(),
        .isEphemeral = info.isEphemeral,
        .edlRootPath = sg ? sg->path().string() : std::string{},
        .moduleName = name().toStdString(),
    };
    if (!d->callSliceClientSimple(
            this,
            PREPARE_RUN_CALL_ID,
            prepReq,
            15,
            IpcCallFlag::TimeoutIsError | IpcCallFlag::SkipWaitOnError))
        return false;

    QElapsedTimer timer;
    timer.start();
    while (state() != ModuleState::READY) {
        handleIncomingControl();
        qApp->processEvents();
        if (state() == ModuleState::ERROR)
            return false;

        // we give modules 30sec to prepare, in case they are very slow
        if (timer.elapsed() > 30 * MS_PER_S) {
            raiseError("Timeout while waiting for module. Module did not transition to 'ready' state in 30 seconds.");
            return false;
        }
    }

    // Final drain to pick up any control events (e.g. settings changes) that arrived
    // concurrently with the READY state. Port changes are acknowledged synchronously
    // via request-response, so they are already applied by the time READY is seen.
    handleIncomingControl();

    // register output port forwarding from exported data streams to internal data transmission
    if (!registerOutPortForwarders())
        return false;
    if (state() == ModuleState::ERROR)
        return false;

    // ensure common metadata on the output ports is up-to-date
    updateCommonStreamMetadata();

    d->portChangesAllowed = false;
    return true;
}
```

--------------------------------

### Build Syntalos on Debian/Ubuntu

Source: https://syntalos.org/tutorials/d1_new-cpp-module

Install the required dependencies for building Syntalos on Debian/Ubuntu, then create a build directory, configure with Meson, and compile with Ninja. Run these commands from the Syntalos source root.

```bash
sudo apt install \
    git ca-certificates \
    cmake \
    gettext \
    libaravis-dev \
    libavcodec-dev \
    libavformat-dev \
    libavutil-dev \
    libegl-dev \
    libeigen3-dev \
    libglib2.0-dev \
    libgstreamer1.0-dev \
    libgstreamer-plugins-base1.0-dev \
    libkf6archive-dev \
    libkf6texteditor-dev \
    libkf6dbusaddons-dev \
    libmimalloc-dev \
    libopencv-dev \
    libpipewire-0.3-dev \
    libqt6opengl6-dev \
    libiceoryx-introspection-dev \
    libqt6svg6-dev \
    libswscale-dev \
    libusb-1.0-0-dev \
    libv4l-dev \
    libxml2-dev \
    libxxhash-dev \
    libsystemd-dev \
    systemd-dev \
    meson \
    ninja-build \
    qt6-base-dev \
    qt6-serialport-dev \
    qt6-multimedia-dev \
    udev \
    uuid-dev
mkdir build && cd build
meson setup --buildtype=debugoptimized ..
ninja
sudo ninja install
```

--------------------------------

### SyncTimer::start

Source: https://syntalos.org/api/files/syclock_8h

Starts the timer, setting the start time to the current master clock time.

```APIDOC
## SyncTimer::start

### Description
Starts the timer, setting the start time to the current master clock time.

### Method
void start() noexcept

```

--------------------------------

### Handle Requirements File and Generate Setup Script

Source: https://syntalos.org/api/files/pyvenvmanager_8cpp

This block processes the requirements file, creates a temporary shell script for environment initialization, and executes the creation process in a terminal.

```cpp
    if (requirementsFile.isEmpty()) {
        // we have no requirements file and want to create a blank venv, so we just create an empty dummy file
        QTextStream rqfOut(&tmpReqFile);
        rqfOut << "\n";
        tmpReqFile.close();
        LOG_INFO(logVEnv, "Creating empty virtualenv {}", venvName);
    } else {
        QFile reqFile(requirementsFile);
        if (!reqFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
            LOG_WARNING(logVEnv, "Unable to open file {} for reading.", requirementsFile);
            return std::unexpected(QStringLiteral("Unable to open requirements file \"%1\": %2")
                                       .arg(requirementsFile, reqFile.errorString()));
        }

        QTextStream rqfIn(&reqFile);
        QTextStream rqfOut(&tmpReqFile);
        while (!rqfIn.atEnd()) {
            QString line = rqfIn.readLine();
            // We can filter requirements here, but currently don't need to do so
            rqfOut << line << "\n";
        }
        tmpReqFile.close();

        LOG_INFO(logVEnv, "Creating virtualenv \"{}\" using requirements file: {}", venvName, requirementsFile);
    }

    LOG_INFO(logVEnv, "Creating new Python virtualenv in: {}", venvDir);
    QTextStream out(&shFile);
    out << "#!/bin/bash\n\n"
        << "run_check() {\n"
        << "    echo -e \"\\033[1;33m-\\033[0m \\033[1m$@\\033[0m\"\n"
        << "    $@\n"
        << "    if [ $? -ne 0 ]\n"
        << "    then\n"
        << "        echo \"\"\n"
        << "        read -p \"Command failed to run. Press [Enter] to exit.\"\n"
        << "        exit 1\n"
        << "    fi\n"
        << "}\n"
        << "export PATH=$PATH:/app/bin\n\n"

        << "cd " << shellQuote(venvDir) << "\n"
        << "run_check virtualenv ."
        << "\n"
        << "run_check source " << shellQuote(QStringLiteral("%1/bin/activate").arg(venvDir)) << "\n"
        << "run_check pip install -r " << shellQuote(tmpRequirementsFname) << "\n"

        << "echo \"\"\n"
        << "read -p \"Success! Press [Enter] to exit.\""
        << "\n";
    shFile.flush();
    shFile.setPermissions(QFileDevice::ExeUser | QFileDevice::ReadUser | QFileDevice::WriteUser);
    shFile.close();

    int ret = runInTerminal(
        tmpCommandFile,
        QStringList(),
        venvDir,
        QStringLiteral("Creating virtual Python environment"));

    shFile.remove();
    tmpReqFile.remove();
    if (ret == 0) {
        injectSyntalosMlinkIntoVenv(venvDir);

        if (!requirementsFile.isEmpty()) {
            const auto b3sumResult = blake3HashForFile(requirementsFile);

            if (!b3sumResult.has_value())
                return std::unexpected(
                    QStringLiteral("Unable to compute requirements checksum: %1").arg(b3sumResult.error()));

            if (!writeRequirementsHashMetadata(venvDir, b3sumResult.value()))
                LOG_WARNING(logVEnv, "Unable to persist requirements metadata for virtualenv: {}", venvName);
        }

        return venvDir;
    }

    // failure, let's try to remove the bad virtualenv (failures to do so are ignored)
    QDir(venvDir).removeRecursively();

    return std::unexpected(
        QStringLiteral("Environment creation failed - refer to the terminal log for more information."));
}
```

--------------------------------

### prepare()

Source: https://syntalos.org/api/classes/classsyntalos_1_1mlinkmodule

Prepares for an experiment run.

```APIDOC
## virtual bool prepare(const RunInfo &info) override

### Description
Prepares for an experiment run.

### Parameters
- **info** (const RunInfo&) - Required - Run information.

### Returns
bool - True if preparation succeeded, false otherwise.
```

--------------------------------

### Open File for Writing

Source: https://syntalos.org/api/files/tsyncfile_8cpp

Opens the file, initializes the header with metadata, and performs 8-byte alignment.

```cpp
bool TimeSyncFileWriter::open(const std::string &modName, const Uuid &collectionId, const MetaStringMap &userData)
{
    if (m_file.is_open())
        m_file.close();

    m_writeFailed = false;
    m_lastError.clear();
    errno = 0;
    m_file.open(m_fname, std::ios::binary | std::ios::out | std::ios::trunc);
    if (!m_file) {
        const auto err = errno;
        m_lastError = std::format(
            "Unable to open file '{}' for writing: {}",
            m_fname,
            err != 0 ? std::error_code(err, std::generic_category()).message() : std::string("Unknown error"));
        return false;
    }

    // ensure block size is not extremely small
    if (m_blockSize >= 0 && m_blockSize < 128)
        m_blockSize = 128;

    m_bIndex = 0;
    XXH3_64bits_reset(m_xxh3State);

    // serialize userData to JSON
    std::ostringstream jsonBuf;
    writeJsonObject(jsonBuf, userData);
    const auto userDataJson = jsonBuf.str();

    // compute creation time
    const auto creationTimeSecs = std::chrono::duration_cast<std::chrono::seconds>(
                                      (m_creationTimeOverride.value_or(std::chrono::system_clock::now()))
                                          .time_since_epoch())
                                      .count();
    m_creationTimeOverride.reset();

    // write file header - magic number raw (not checksummed)
    writeRawLE<uint64_t>(TSYNC_FILE_MAGIC);

    csWriteValue<uint16_t>(TSYNC_FILE_VERSION_MAJOR);
    csWriteValue<uint16_t>(TSYNC_FILE_VERSION_MINOR);
    csWriteValue<int64_t>(static_cast<int64_t>(creationTimeSecs));

    csWriteValue(modName);
    csWriteValue(collectionId.toHex()); // UUID as hex string
    csWriteValue(userDataJson);

    csWriteValue<uint16_t>(static_cast<uint16_t>(m_tsMode));
    csWriteValue<int32_t>(m_blockSize);

    csWriteValue(m_timeNames.first);
    csWriteValue<uint16_t>(static_cast<uint16_t>(m_timeUnits.first));
    csWriteValue<uint16_t>(static_cast<uint16_t>(m_time1DType));

    csWriteValue(m_timeNames.second);
    csWriteValue<uint16_t>(static_cast<uint16_t>(m_timeUnits.second));
    csWriteValue<uint16_t>(static_cast<uint16_t>(m_time2DType));

    m_file.flush();
    if (!checkStreamState("Writing header"))
        return false;
    const auto headerBytes = static_cast<int>(m_file.tellp());
    if (headerBytes <= 0) {
        m_writeFailed = true;
        m_lastError = std::format("Could not determine amount of bytes written for header of '{}'.", m_fname);
        return false;
    }
    const int padding = (headerBytes * -1) & (8 - 1); // 8-byte align header
    for (int i = 0; i < padding; i++)
        csWriteValue<uint8_t>(0);

    // write end of header and header CRC-32
    writeBlockTerminator(false);
    m_file.flush();
    return checkStreamState("Writing header");
}
```

--------------------------------

### Install Syntalos via Flatpak and allow serial device access

Source: https://syntalos.org/get

Install Syntalos via Flatpak from Flathub and grant the current user access to serial devices. Requires Flatpak and Flathub to be configured. The Flatpak command installs the org.syntalos.syntalos application.

```bash
flatpak install flathub org.syntalos.syntalos
```

```bash
sudo usermod -a -G dialout $USER
```

--------------------------------

### SecondaryClockSynchronizer.start

Source: https://syntalos.org/docs/pysy-mlink-api

Initialize and begin synchronization. Returns `True` on success.

```APIDOC
## SecondaryClockSynchronizer.start

### Description
Initialize and begin synchronization. Returns `True` on success.

### Method Signature
`start() -> bool`

### Parameters
None

### Returns
- **bool** - `True` on success.
```

--------------------------------

### Install C++ toolchain on Debian-based systems

Source: https://syntalos.org/docs/modules/cpp-workbench

Command to install the necessary compiler and build tools required for the C++ Workbench module on Debian-based Linux distributions.

```bash
sudo apt install gcc g++ pkgconf meson ninja-build
```

--------------------------------

### AbstractModule window show and position with QMetaObject::invokeMethod

Source: https://syntalos.org/api/files/moduleapi_8cpp

Shows how AbstractModule positions and shows a window via QMetaObject::invokeMethod with a queued connection. Handles Wayland (using Winpos::WindowPositioner) and X11 fallback, centering vertically on the cursor on first show and restoring the saved position on re-show. Also raises and activates the window, noting Wayland and X11 behavior.

```cpp
QMetaObject::invokeMethod(
            w,
            [w, needsInitialPos, cursorPos]() {
                w->show();
#ifdef SY_PREFER_WAYLAND
                auto wnd = w->windowHandle();
                auto posHelper = wnd ? wnd->findChild<Winpos::WindowPositioner *>() : nullptr;
                if (wnd && !posHelper)
                    posHelper = new Winpos::WindowPositioner(wnd, wnd);
                if (posHelper) {
                    if (needsInitialPos) {
                        // First show: center vertically on the cursor.
                        // cursorPos is zone-relative (screen origin subtracted above).
                        // height() is valid here; show() has triggered the layout pass.
                        auto pos = cursorPos;
                        pos.setY(pos.y() - (w->height() / 2));
                        posHelper->move(pos);
                    } else {
                        // Re-show: restore the last compositor-confirmed position.
                        // On Wayland the surface is destroyed on hide() and recreated
                        // on show(), so the compositor would otherwise reassign a new
                        // default placement. Calling move() here queues the saved
                        // position as pendingPosition; WindowPositioner applies it in
                        // initializeWayland() once the surface role is created.
                        posHelper->move(posHelper->position());
                    }
                }
#else
                if (needsInitialPos) {
                    // First show only: on X11 without Winpos, Qt retains the widget
                    // position across hide()/show() cycles so we only need to set it
                    // the very first time.  cursorPos is in global screen coordinates.
                    auto pos = cursorPos;
                    pos.setY(pos.y() - (w->height() / 2));
                    w->move(pos);
                }
#endif
                // raise() is a no-op on Wayland, but activate does bring
                // the window to the front if it was hidden on most Wayland
                // compositors... On X11, raise() is enough, but activating
                // the window too does not hurt and is what the user expects.
                w->raise();
                w->activateWindow();
            },
            Qt::QueuedConnection);
    }
}
```

--------------------------------

### showSettingsUi()

Source: https://syntalos.org/api/classes/classsyntalos_1_1mlinkmodule

Shows the configuration UI of this module.

```APIDOC
## virtual void showSettingsUi() override

### Description
Shows the configuration UI of this module.
```

--------------------------------

### FUNC_DONE_TIMESTAMP macro definition

Source: https://syntalos.org/api/files/syclock_8h

Computes a timestamp for when a function completed, not the average between start and end time. Takes a starting timepoint and returns the time since that point in microseconds.

```cpp
#define FUNC_DONE_TIMESTAMP(
    INIT_TIME,
    F
)
    ({                                                                                   \
        F;                                                                               \
        std::chrono::duration_cast<microseconds_t>(symaster_clock::now() - (INIT_TIME)); \
    })
```

--------------------------------

### mainWinState / setMainWinState

Source: https://syntalos.org/api/classes/classsyntalos_1_1globalconfig

Gets or sets the main window state (e.g., toolbar/dock layout) as a QByteArray.

```APIDOC
## QByteArray mainWinState() const

### Description
Returns the main window state.

### Returns
- **QByteArray** - The state data.

## void setMainWinState(const QByteArray &state)

### Description
Sets the main window state.

### Parameters
- **state** (const QByteArray&) - Required - The state data.

### Returns
- void
```

--------------------------------

### ACK failure JSON example

Source: https://syntalos.org/docs/network-ctl-protocol

Example of an ACK message on failure, adding an `"error"` field with a human-readable error message. The `success` field is `false`.

```json
{
  ...
  "success": false,
  "error": "Module 'camera' failed to initialize"
}
```