JunKimmmy/USBPowerMeter8A compact USB-C passthrough power meter that displays real-time voltage, current, and power on an integrated 128×64 OLED screen.
USBPowerMeter is an open-source printed circuit board by JunKimmmy, from the JunKimmmy/USBPowerMeter repository on GitHub. It is a 4-layer board of 33.5 × 24 mm with 84 parts on 80 nets, routed with 499 tracks and 153 vias.
It is built around the INA238AIDGSR, LMR36006FSC3RNXRQ1 and MSMCP1640T-I/CHY, with the TS24CA, BRCS5P06MA and BZT52C12 among its other parts. Its parts include 25 capacitors, 21 resistors, 4 ICs, 4 transistors and 4 connectors. It belongs with the STM32 boards of this library.
A compact USB-C passthrough power meter that displays real-time voltage, current, and power on an integrated 128×64 OLED screen. It sits inline between a USB-C charger and a device — all USB signals pass through transparently while the onboard MCU samples the INA238 power monitor and drives the display.
| Parameter | Value |
|---|---|
| Input voltage range | 0.3 V – 48 V |
| Max continuous current | 5 A |
| ADC resolution | 16-bit (INA238) |
| Display | 128×64 OLED (SSD1315), I²C |
| MCU | STM32G030K6T6 (LQFP-32) |
| MCU/peripheral supply | 3.3 V buck from VBUS |
| OLED supply | 3.8 V boost |
| Passthrough | USB-C male + USB-C female |
Designed in KiCad 10. All custom symbols and footprints are in libs/.
| IC | Function |
|---|---|
| INA238 | 16-bit high-precision power/current/voltage monitor (shunt + bus voltage) |
| STM32G030K6T6 | Measurement processing, graph engine, display control |
| SSD1315 | 128×64 OLED controller (I²C) |
| LMR36006 | VBUS-to-3.3 V synchronous buck regulator |
| DGS0010A | 3.8 V boost supply for OLED |
3D-printable enclosure designed in OnShape: View in OnShape
All components were hand-soldered. Firmware was flashed over SWD using an ST-Link V3 Mini.
| Video | Description |
|---|---|
| PCB Assembly | Hand-soldering all components onto the board |
| Display Testing | OLED display bring-up and meter UI |
| Buzzer Testing | Buzzer tone testing |
The meter was tested by powering a mini hotplate (~20 V supply). The power graph clearly shows the hotplate's heating element ramping up linearly from 0 W as it heats, plateauing around 42 W once it reaches temperature, then dropping sharply when switched off.
Written in C using STM32CubeIDE with the STM32 HAL. Targets the STM32G030K6T6.
| Mode | Description |
|---|---|
| Main Meter | Two-column header (VOLT / AMPS), large 2× readout, full-width power row, footer with running averages |
| Current Graph | 128-sample rolling plot of current (mA), dashed line = running average, header shows live + avg + peak |
| Power Graph | Same layout as current graph but for power (mW) |
Navigate between modes with the onboard buttons.
| File | Purpose |
|---|---|
main.c | HAL init, main loop, buzzer tone engine |
meter.c | Display screens, graph circular buffer, button debounce |
oled.c | SSD1315 OLED driver (I²C, page-mode framebuffer) |
ina238.c | INA238 driver — shunt/bus voltage, current, power registers |
boot.c | Animated boot screen |
banana.c / banana_frames.c | Dancing-banana easter egg animation |
generate_frames.py | Converts 249×246 GIF PROGMEM bitmaps to SSD1315 page-format C arrays |
Firmware/ST/ in STM32CubeIDESTM32G030K6TX_FLASH.ldUSBpowermeter.kicad_pro KiCad project
USBpowermeter.kicad_sch Schematic
USBpowermeter.kicad_pcb PCB layout
libs/
Library.kicad_sym Custom schematic symbols
Library.pretty/ Custom footprints
3dmodels/ STEP models for 3D viewer
Firmware/ST/
Core/Src/ Application source (C)
Core/Inc/ Application headers
Drivers/ STM32 HAL + CMSIS
generate_frames.py Bitmap conversion tool
images/ PCB renders, enclosure CAD, real photos
videos/ Assembly and testing footage| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | TP4 | TestPoint:TestPoint_Pad_D1.0mm | TP18, TP20, TP21, TP22, TP23, TP24, TP25, TP27, TP28 |
| 8 | 1uF | Capacitor_SMD:C_0402_1005Metric | C2, C4, C6, C10, C12, C13, C27, C28 |
| 6 | 100nF | Capacitor_SMD:C_0402_1005Metric | C3, C5, C9, C11, C22, C23 |
| 6 | 10kΩ | Resistor_SMD:R_0402_1005Metric | R9, R14, R23, R24, R25, R26 |
| 6 | LOGO | LOGO | G***, G***, G***, G***, G***, G*** |
| 4 | 10uF | Capacitor_SMD:C_0402_1005Metric | C15, C16, C17, C21 |
| 3 | 100kΩ | Resistor_SMD:R_0402_1005Metric | R7, R8, R13 |
| 3 | 10nF | Capacitor_SMD:C_0402_1005Metric | C24, C29, C30 |
| 3 | TS24CA | Library:SW-SMD_2P-TS24CA | SW3, SW4, SW6 |
| 2 | 10R | Resistor_SMD:R_0402_1005Metric | R4, R5 |
| 2 | 4.7kΩ | Resistor_SMD:R_0402_1005Metric | R2, R3 |
| 2 | 47kΩ | Resistor_SMD:R_0402_1005Metric | R20, R21 |
| 2 | TP5 | TestPoint:TestPoint_Pad_2.0x2.0mm | TP19, TP26 |
| 1 | 100nF | Capacitor_SMD:C_0603_1608Metric | C1 |
| 1 | 100Ω | Resistor_SMD:R_0402_1005Metric | R12 |
| 1 | 10uF | Capacitor_SMD:C_0805_2012Metric | C18 |
| 1 | 1MΩ | Resistor_SMD:R_0402_1005Metric | R15 |
| 1 | 2.2uF | Capacitor_SMD:C_0402_1005Metric | C26 |
| 1 | 215k | Resistor_SMD:R_0402_1005Metric | R10 |
| 1 | 22uH | Inductor_SMD:L_APV_ANR3015 | L1 |
| 1 | 2N7002K_C414015 | Package_TO_SOT_SMD:SOT-23-3 | Q1 |
| 1 | 330kΩ | Resistor_SMD:R_0402_1005Metric | R19 |
| 1 | 4.7uF | Capacitor_SMD:C_0402_1005Metric | C25 |
| 1 | 4.7uH | Inductor_SMD:L_0603_1608Metric | L2 |
| 1 | 5mΩ | Resistor_SMD:R_1206_3216Metric | R1 |
| 1 | 620kΩ | Resistor_SMD:R_0402_1005Metric | R16 |
| 1 | BRCS5P06MA | Library:SOT-23-3_L2.9-W1.3-P1.90-LS2.4-BR | Q2 |
| 1 | BZT52C12 | Library:SOD-123_L2.7-W1.6-LS3.7-RD | D4 |
| 1 | FDN335N | Package_TO_SOT_SMD:SOT-23-3 | Q4 |
| 1 | FDN338P_C347511 | Package_TO_SOT_SMD:SOT-23-3 | Q3 |
| 1 | FPC-05FB-30PH20 | Library:FPC-SMD_30P-P0.50_FPC-05FB-30PH20 | J3 |
| 1 | HX PZ1.27-2X7P TP | Library:HDR-SMD_14P-P1.27_HX-PZ1.27-2X7P-TP | J4 |
| 1 | INA238AIDGSR | Library:VSSOP-10_L3.0-W3.0-P0.50-LS4.9-BL | U2 |
| 1 | LMR36006FSC3RNXRQ1 | Library:VQFN-12_L3.0-W2.0-P0.65-BL_TI_RNX | U3 |
| 1 | MINI MSK12CO2 | Library:SW-SMD_MSK12CO2 | SW5 |
| 1 | MLT-5020 | C94598:BUZ-SMD_L5.0-W5.5-P4.60 | BZ1 |
| 1 | MSMCP1640T-I/CHY | Package_TO_SOT_SMD:SOT-23-6 | U4 |
| 1 | SMAJ58CA_C2943847 | Library:SMA_L4.2-W2.6-LS5.0-BI | D1 |
| 1 | STM32G030K6T6TR | Library:LQFP-32_L7.0-W7.0-P0.80-LS9.0-BL | U1 |
| 1 | USB4155-03-C | Library_new:GCT_USB4155-03-C_REVA | J5 |
| 1 | USB4215-03-A | Library_new:CONN_8p94X6p5X3p16_12L_GCC | J1 |
It measures 33.5 × 24 mm and has 4 copper layers, 1.6 mm thick.
84 parts, built around the INA238AIDGSR, LMR36006FSC3RNXRQ1, MSMCP1640T-I/CHY and TS24CA. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
From the JunKimmmy/USBPowerMeter repository on GitHub, at the commit this page was made from: the board is USBpowermeter.kicad_pcb and its schematic USBpowermeter.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask JunKimmmy before reusing the design.
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