Power Tab¶
The Power tab (tab 3) displays power-related data. The content varies significantly depending on which board is detected.
Pi 5: PMIC power rails¶
The Raspberry Pi 5 includes a PMIC (Power Management IC) that provides detailed per-rail power telemetry via vcgencmd pmic_read_adc.
Rail table¶
The tab displays a table with all 12 voltage and current rail pairs:
| Column | Description |
|---|---|
| Rail | Rail name (e.g., VDD_CORE, VDD_CPU) |
| Voltage | Rail voltage in volts |
| Current | Rail current in amps |
| Power | Calculated power in watts (V x I) |
Key rails¶
- VDD_CORE -- main SoC core voltage
- VDD_CPU -- CPU power rail
- VDD_IO -- I/O voltage
- EXT5V_V -- input voltage from the USB-C power supply
- BATT_V -- RTC battery voltage (if present)
Estimated total wattage¶
The estimated real power draw is calculated as:
This includes a correction factor to account for PMIC conversion losses.
A sparkline tracks total wattage over time.
Pi 4B: Voltage readings¶
On the Raspberry Pi 4 Model B, power monitoring uses vcgencmd measure_volts to read voltage levels for:
- core -- SoC core voltage
- sdram_c -- SDRAM controller voltage
- sdram_i -- SDRAM I/O voltage
- sdram_p -- SDRAM PHY voltage
Note
The Pi 4B does not have a PMIC with current sensing, so only voltage values are displayed. Current and wattage calculations are not available.
Pi Zero 2W¶
The Pi Zero 2W supports the same measure_volts readings as the Pi 4B (core and SDRAM voltages).
PCIe link status (Pi 5)¶
If the Pi 5 has a PCIe device connected (e.g., an NVMe SSD via HAT+), this section shows:
- Link generation (e.g., Gen 2, Gen 3)
- Lane width (e.g., x1)
- Downgrade detection -- warns if the link is running below its maximum capability
PCIe data is read from /sys/bus/pci/devices/*/current_link_speed and /sys/bus/pci/devices/*/current_link_width.
PoE status (Pi 5, Pi 4B)¶
If a PoE (Power over Ethernet) HAT is detected, this section shows:
- PoE status -- whether power is being supplied via PoE
- Current draw -- from
/sys/class/power_supply/rpi-poe*
Note
PoE detection requires a PoE HAT or PoE+ HAT to be installed. If no PoE hardware is detected, this section is hidden.
Graceful degradation¶
The Power tab adapts to available hardware:
| Board | PMIC rails | Voltages | PCIe | PoE |
|---|---|---|---|---|
| Pi 5 | Yes | -- | Yes | Yes |
| Pi 4B | -- | Yes | -- | Yes |
| Zero 2W | -- | Yes | -- | -- |
| Generic Linux | -- | -- | -- | -- |
On boards without any power features, the tab displays a message indicating that no power data is available.