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Measure the target’s current, voltage, and energy while it runs a known workload, such as boot, a radio burst, or sleep. Use this page to choose an instrument and to work with the Monitor’s Power tab, which the PPK2 and Joulescope share. Setup, wiring, and limits for each instrument are on its own page. Before you start, decide on the instrument, wiring, supply, workload, and measurement duration.

Choose the instrument

Nordic PPK2

Power the target at 800–5000 mV in source-meter mode, or measure current from an external supply in ampere-meter mode.

Joulescope

Measure current and voltage inline with an external supply, with statistics, streaming, and JLS recordings.

Digilent WaveForms

Power a small target from the device’s supplies and record their voltage and current in the Power tab. Analog input recordings open in Oscilloscope.
Follow the wiring and limits for your exact model and front panel. Before you measure, check for other power paths into the target, such as USB or a debugger, because they change the reading. If you remove a board’s current-measurement jumper, put it back before you return to ordinary debugging.

Stream live power in the Monitor

Use the Monitor’s Power tab to watch a PPK2 or Joulescope in real time without writing a script.
1

Open a Power tab for the instrument

In the Monitor, select +. Under On the bench, select your PPK2 or Joulescope. A Power tab opens, bound to that device. You can also open Power from Views and choose the instrument from the device chip at the start of the toolbar.
2

Approve setup

If the toolbar shows Set up & connect, select it. Selecting it approves the installs the instrument needs, and the toolbar shows each step. See Connect a bench instrument for the device states.
3

Choose the settings

In the Setup panel, choose the sample rate and the instrument’s options. To show or hide the panel, select the Power setup chip, the settings summary next to the device chip in the toolbar. See PPK2 or Joulescope.
4

Start the stream

Select Start. The status changes from Connecting to Live, and readouts appear on the chart.
Embedder saves the Setup values for each device when you select Start. DUT power is never restored automatically.

Control the stream

While the stream runs, the Power setup chip is locked and the Setup panel closes. Stop the stream to change the settings. The device chip is also locked while the stream runs or DUT power is on. When Embedder or a hardware script measures power, the Power tab shows that measurement’s live preview in place of the stream controls. Select New capture to leave the preview.

Share the instrument with Embedder

A live stream uses only its instrument, so Embedder can build, flash, or debug the board from chat while the stream runs. When a chat needs the same PPK2 or Joulescope, Embedder stops the stream, saves the chart window as a power capture, and shows Paused: with the chat’s name and the instrument it needs. The stream starts again about 10 seconds after the chat finishes with the instrument. A Joulescope stream, or a PPK2 stream in source-meter mode, doesn’t restart if a chat still holds the board at that moment, and the tab stays on Paused:. When the chat has finished, select Stop, then Start. Check the DUT power switch before you start, because a stream started with it off keeps the target’s current path off. While a chat holds the board, the toolbar shows In use by and the chat’s name. Start and Resume are unavailable, and you can’t turn DUT power on. A stream that is already running keeps its Pause and Stop controls. Embedder refuses anything that would switch the target’s power off while the chat holds the board:
  • Turning DUT power off reports “Hardware is in use by another workflow”.
  • Stopping a PPK2 stream in source-meter mode reports “An agent is using the board this PPK2 powers”.
Try again when the chat finishes. Run /hardware-queue to see what holds the board.

Control DUT power

The DUT power switch starts off, and a stream started with it off keeps the target’s current path off. Turn DUT power on before or during a stream.
  • Joulescope: the switch connects or disconnects the current path from your external supply to the target. It doesn’t set a supply voltage. If a JS320 fuse has tripped, turning DUT power on shows an error instead of streaming a flat 0 A trace. Fix the overcurrent cause, then ask Embedder to clear the fuse.
  • PPK2 in source-meter mode: the switch turns the PPK2’s output to the target on or off. DUT power turns off when the stream stops. Turn DUT power off before you change the mode or voltage.
  • PPK2 in ampere-meter mode: there is no DUT power switch, because the external supply powers the target.

Read the chart

The chart shows a rolling window of the most recent samples.
  • The readouts on the chart show the latest current, voltage, and power, each with its average and peak. The Total row shows the charge and energy for the samples in the chart.
  • The readouts also show the sample rate. If the instrument applies a different rate than you requested, the rate is marked actual. Elapsed time appears beside the Live status in the toolbar.
  • When the chart has more than one series, select a readout to hide or show its series.
  • Drag across a region to zoom both axes. Select Reset zoom, or double-click the chart, to return to the full window.

Record a longer test

Define the workload and its settling period, measure for the required interval, and save the trace or statistics.
  • For long Joulescope tests, use statistics, streaming, or a JLS recording. Keep a one-shot Joulescope capture to 60 seconds or less.
  • For long PPK2 tests, use a slow live stream or a background script. See PPK2.
  • For a long live view, choose a sample rate where 4,000 windows cover the interval, because Stop saves only the most recent 4,000 windows. At 2 Hz, they cover about 33 minutes. At 100 Hz, they cover 40 seconds. A live stream ends on its own after 24 hours.
Keep the firmware revision, supply voltage, duration, and any jumper changes with the result. Restore the board’s normal connections before ordinary debugging.

Compare runs

Embedder saves each power capture in its own folder under .embedder/captures/ in your project, grouped by chat session. This covers the capture a live stream saves when you select Stop and the Joulescope captures Embedder takes from chat. Each folder holds: To reopen a capture, select Capture history in the Power tab. When a live stream stops, Embedder also adds the saved capture’s path to the open chat, so you can ask about that run without looking up the folder. To compare two runs, measure the same workload over the same interval, then name the captures or their folders:

Correlate activity

Hold the target in a known firmware state, or use Joulescope digital markers. When marker results don’t have timestamps aligned to current samples, measure each settled state separately and compare them. See Combined workflows for relating power to firmware behavior.

Troubleshoot

  • Current reads zero: check the current path, the supply, and DUT power.
  • Readings are unexpected: check for other power sources and the voltage-sense wiring.
  • “A run started outside chat cannot approve installs”: select Set up & connect in the toolbar, or ask Embedder in chat to start the measurement so you can approve the install.
  • “Hardware is in use by another workflow”: a chat holds the board. Wait for it to finish, or run /hardware-queue to see what holds it.
  • “The PPK2 is in use by an agent” or “The Joulescope is in use by an agent”: a chat is using the instrument. Start the stream after the chat finishes with it.
  • Stream shows “Paused:”: a chat needed the instrument. The stream restarts on its own about 10 seconds after the chat finishes. If it’s still paused after that, select Stop, then Start.
For device-specific problems, see the troubleshooting for PPK2, Joulescope, or Digilent.
Last modified on November 13, 2026