> ## Documentation Index > Fetch the complete documentation index at: https://docs.embedder.com/llms.txt > Use this file to discover all available pages before exploring further. # Joulescope > Measure current, voltage, and energy with JS110, JS220, or JS320. Use a Joulescope inline with an external supply to measure current and voltage during a known firmware workload. Captures appear in the Monitor's **Power** tab. Identify the model and serial number before measuring; JS110, JS220, and JS320 differ in ranges, sampling, and digital I/O. ## Prepare Connect Joulescope by USB, close competing applications, and complete Embedder's requested dependency setup. JS320 requires Python 3.12 or newer and `pyjoulescope_driver` 2.3.4 or newer. Device firmware older than 1.1.3 is rejected on JS320. ## Wire the current and voltage paths Joulescope does not supply voltage. Connect it between an external supply and the target using the wiring for the installed model and front panel. For a JS110-style panel, supply connects to IN and the target to OUT. For JS220 or JS320 terminals, route supply positive through `I+` and `I-` to target VDD, connect the voltage-sense terminals as required, and share the reference ground. In a two-wire setup, tie `V+` to `I+`; for Kelvin sensing, sense voltage at the target. Use the exact device limits. Enabling the DUT current path permits current from the external supply; it does not set a supply voltage. On JS320, resolve the cause of a tripped fuse before asking Embedder to clear it and re-enable that path. ## Measure a workload ```text theme={"system"} The JS220 is wired inline to an external 3.3 V supply. Capture current and voltage for three seconds during the idle workload and open the Power view. Report current, voltage, power, and energy for the capture. ``` Specify the supply, settling period, workload, duration, and final current-path state. Use automatic current ranging unless a known workload needs a fixed range. In a [hardware script](/debug-mode/hardware-scripts), `joulescope_measure()` performs a bounded capture; one-shot captures are limited to **60 seconds**. When choosing ranges and sample rates, use the connected model's supported settings: * **JS110:** supports the 2 A current range and 5 V voltage range; host samples can reach 2 MS/s. * **JS220:** uses a 10 A range instead of JS110's 2 A range, supports 15 V or 2 V voltage ranges, and caps host output at 1 MS/s. * **JS320:** supports 15 V or 2 V voltage ranges and a configurable autorange window. Its supported sample rates differ from the earlier models; ask for the accepted rates rather than reusing a JS110/JS220 rate. These are measurement settings, not permission to exceed the device's input ratings. Check the applied settings before comparing results. ## Record a longer test For a live view, open setup in the Monitor's **Power** tab and choose **Joulescope**, then select the available current and voltage ranges. Press **Start**, use **Pause** / **Resume** as needed, and press **Stop** to finish and save a capture. The live view's **Sample rate** controls statistics windows per second, separately from the raw acquisition sample rate. The DUT power control enables or disables the external supply's current path. Choose the result you need: * **Periodic statistics:** request current, voltage, and power statistics at a defined interval. Reset charge and energy accumulators when starting a new workload. A single statistics read returns the latest statistics window, not an aggregate of the entire time spent waiting. * **Live samples:** start a stream, read samples during the test, then stop it and save the result you need. * **Raw recording:** record selected current, voltage, or power signals to a `.jls` file, then stop the recording and open its result. JLS recordings support longer tests and offline inspection in Joulescope software. ```text theme={"system"} Record current and voltage to idle-cycle.jls during a two-minute workload. Stop recording when the workload ends and show the saved recording in Power. Keep the external supply unchanged throughout the test. ``` Stop a live sample stream before starting a JLS recording. Record the workload, firmware revision, supply voltage, and settling period with the result so another run is comparable. To revisit a completed recording, give its `.jls` path and ask Embedder to open it in **Power**. This view requires both current and voltage signals in the recording. Long recordings are summarized for display; retain the JLS file for full sample-level inspection. ## Correlate digital activity For digital markers, give the GPI pin and target logic voltage. JS110 supports configurable I/O voltage; JS220 uses its internal 3.3 V reference or an externally wired Vref. On JS320, choose internal 3.3 V or the external VREF connection explicitly; wire external VREF to the target's logic supply when using it. You can read GPI states, drive supported GPO pins, or measure between observed GPI edges. Specify a maximum duration and the final GPO state. The GPI-window measurement uses software polling and is suitable for longer state windows, not microsecond timing. **JS220** can decode two 8N1 UART streams while measuring power. JS110 and JS320 do not expose this UART helper. ```text theme={"system"} Decode the target TX line on JS220 gpi1 at 115200 baud while measuring for five seconds. Report the received text and the whole-capture current statistics. ``` The UART result contains bytes without timestamps aligned to current samples. Use it to confirm that markers arrived during a capture. To compare current by state, hold the target in each known state and measure settled intervals separately. ## Update JS320 firmware If a JS320 needs a firmware update, ask Embedder to prepare a dedicated hardware script using `joulescope_firmware_update()`. Stop measurements and disconnect the software session first, while leaving USB plugged in. Review and approve the update separately from a measurement; after it finishes, reconnect and verify the reported firmware version. ## Configure a live stream Set the sample rate before you start. The rate counts statistics windows per second, not raw ADC samples. Each live sample is one on-device window with mean, minimum, and maximum values. * JS110 and JS220 serve the `1`, `2`, `5`, `10`, `20`, `50`, and `100` Hz ladder. * JS320 serves `1` Hz through `10` kHz. * The device rounds a request to a rate it can serve. The toolbar shows the applied rate when it differs from the request. Pick the voltage range and current range in the Setup panel before starting. A JS320 exposes a minimum and maximum current-range window; a JS110 or JS220 selects a single current range. See [live power controls](/debug-mode/power-analyzer#stream-live-power-in-the-monitor) for pausing, recording, and stopping the stream. ## Troubleshoot * **Zero current:** verify the current path and external supply; check for a tripped JS320 fuse. * **Wrong voltage:** check voltage-sense wiring and the selected measurement range. * **Range or sample rate rejected:** use settings supported by that model. * **Device unavailable:** close competing applications and complete setup; JS320 may require a Python, driver, or firmware update. * **Long capture fails:** use statistics, streaming, or a JLS recording instead of a one-shot capture. * **Digital marker missing:** verify the pin, ground, I/O reference, and signal duration. See [Combined workflows](/debug-mode/combined-workflows) for relating power to firmware behavior.