Live plots and math channels

Embedder plots numeric telemetry from serial or RTT streams in the Monitor. You can view live time series, pair channels in an XY plot, show text status channels, and compute derived channels without changing firmware. The live plot UI requires the Embedder VS Code extension.

Emit Teleplot data

Prefix each telemetry line with >:

Serial.printf(">die_temp:%.2f§°C\r\n", die_temp);
Serial.printf(">motor_rpm:%d§RPM\r\n", motor_rpm);
Serial.printf(">accel_x:%lu:%.4f§g\r\n", millis(), accel_x);
Serial.printf(">fsm_state:%s|t\r\n", state_name);

The accepted forms are:

>channel:value
>channel:timestamp:value
>channel:value§unit
>channel:textValue|t

channel identifies the source channel.
timestamp is an optional monotonic millisecond value.
unit labels the Y axis.
|t marks a text or status channel.

Lines without > remain normal serial output and are ignored by the plot parser. Emit one channel per line, and log from the main loop or a task rather than a tight interrupt handler. Device timestamps preserve sample spacing when the serial transport batches data. The plotter anchors the first device timestamp to wall time. A backward jump greater than one second creates a new anchor, which handles device restarts.

Start and inspect a plot

Ask Embedder to plot the required signals:

Plot battery_voltage and charge_current from the connected device.
Put charge_current on the right axis.

The agent reads the firmware or serial history, starts the stream with plot_start, and checks the discovered names with plot_status. Starting a new live plot requires hardware confirmation and holds an exclusive live-session hardware lease for that target. plot_status reports:

Every active port
Discovered numeric channels and units
The saved session ID
The complete math-channel list for each port

With one active port, later plot operations can omit port. With several active ports, specify it.

Parse another serial format

If you cannot change the firmware, pass a JavaScript regular expression to plot_start. It must contain named channel and value groups:

{
  "transform_regex": "^\\[SENSOR\\] (?<channel>\\w+)=(?<value>[\\d.]+)(?<unit>[A-Za-z°]+)?$"
}

You can also capture timestamp in milliseconds and unit. Python-style (?P<name>...) groups are not accepted. When no Teleplot channels are detected, Embedder captures sample unmatched lines and asks the agent to prepare or correct the expression. It tests a new expression against buffered samples and reports whether it matched.

Configure source channels

plot_start also updates an active plot without restarting it. You can configure one channel or a batch with:

Visibility
Color
Left or right Y axis
Display label
Unit override
Y-axis minimum and maximum

You can filter incoming data to named channels when starting the stream. Text channels appear in a status panel rather than on a numeric axis. The plot toolbar lets you:

Pause or resume rendering
Clear the current data
Select all data, 30 seconds, 1 minute, or 5 minutes
Toggle source and math channel visibility
Rename the recording
Export CSV data
Save the current plot configuration

Use XY mode

XY mode aligns independently emitted channels by timestamp and plots one variable against another:

{
  "plot_mode": "xy",
  "xy_pairs": [
    {
      "x_channel": "voltage",
      "y_channel": "current",
      "label": "I-V curve"
    }
  ]
}

Only paired channels appear in XY mode. Switch back with:

{
  "plot_mode": "timeSeries"
}

For a pair across ports, use the stored channel names:

{
  "plot_mode": "xy",
  "xy_pairs": [
    {
      "x_channel": "COM3/voltage",
      "y_channel": "COM4/current"
    }
  ]
}

Create math channels

Math channels are evaluated in the plot view from the latest source values. Call plot_status first because references are case-sensitive and must use names the plot has discovered.

{
  "channels": [
    {
      "name": "power",
      "expression": "voltage * current",
      "unit": "W",
      "axis": "right"
    },
    {
      "name": "temp_smooth",
      "expression": "lowpass(temp, 5)",
      "unit": "°C"
    }
  ]
}

Each plot_set_math_channels call replaces the full list. Read the existing list, modify it, and send every channel you want to keep. Pass an empty list to clear all math channels. Math channel names must be unique and should not reuse a source channel name. A missing source produces a warning from the tool and a gap in the chart until all dependencies have data.

Expression grammar

Expressions accept:

Operators: +, -, *, /, unary + and -, and parentheses
Numeric literals: integers, decimals, and scientific notation
Bare channel names, such as voltage
Port-qualified names with a dot, such as COM3.voltage
Nested function calls

Conditions, comparisons, strings, assignments, and arbitrary JavaScript are rejected. The stateless functions are:

abs(x)
sqrt(x)
pow(x, n)
exp(x)
log(x)
min(a, b, ...)
max(a, b, ...)

The stateful functions are:

lowpass(x, cutoffHz) and highpass(x, cutoffHz), with a positive literal cutoff
ema(x, alpha), with a literal alpha from 0 to 1
moving_avg(x, window) and median(x, window), with a positive integer window
derivative(x) and integral(x)
rolling_mean(x, window) and rolling_std(x, window)
rolling_min(x, window) and rolling_max(x, window)
rolling_p2p(x, window) and rolling_rms(x, window)

Each stateful function occurrence owns separate state. Replacing the math-channel list resets all filter state. derivative uses seconds between source timestamps and starts with a gap. integral uses trapezoidal accumulation. In a multi-port plot, a bare name resolves to a source with that name. If more than one port emits the same name, qualify it with PORT.channel. A slash remains the division operator inside expressions.

Save and load recordings

Live numeric points are recorded under:

.embedder/plots

Each recording has tab-separated CSV data and JSON metadata with its port, baud rate, channels, timestamps, and point count. plot_load can list recordings or find one by session name, session ID, or channel name. The store keeps the 50 most recent completed sessions. plot_stop ends one port or every active plot. It finalizes the recording, clears its math-channel cache, releases the hardware activity, and can copy a single recording to a requested CSV path.

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Live plots and math channels

Emit Teleplot data

Start and inspect a plot

Parse another serial format

Configure source channels

Use XY mode

Create math channels

Expression grammar

Save and load recordings

​Emit Teleplot data

​Start and inspect a plot

​Parse another serial format

​Configure source channels

​Use XY mode

​Create math channels

​Expression grammar

​Save and load recordings

Emit Teleplot data

Start and inspect a plot

Parse another serial format

Configure source channels

Use XY mode

Create math channels

Expression grammar

Save and load recordings