nitefood/opsum5OPSUM - The Open PSU Meter project
Open PSU Meter ESP32 is an open-source printed circuit board by nitefood, from the nitefood/opsum repository on GitHub, published under the MIT licence. It is a 2-layer board of 80 × 50 mm with 51 parts on 84 nets, routed with 307 tracks and 268 vias.
It is built around the B0505S-2WR3, ADUM1201ARZ-RL7 and CH340N, with the INA226AIDGSR, CC0603KRX7R9BB104 and CL31A476MPHNNNE among its other parts. Its parts include 15 capacitors, 14 resistors, 6 diodes, 4 ICs and 2 connectors. It belongs with the power boards and the ESP32 boards of this library.
OPSUM is a DC voltmeter and ammeter board with 4mm banana socket inputs, that enables measuring and logging voltage, current and power, even when using a bench PSU that has no builtin telemetry feature. Communication between the board and the host happens via UART protocol over a dedicated USB port that is galvanically isolated from the PSU/DUT (power supply unit and device under test) side of the PCB, in order to protect the host-side (PC) from potentially destructive shorts or spikes happening on the DUT side.
This repository is structured as a monorepo: hardware design files, enclosure CAD files, firmware, host-side GUI tools, release binaries, communication protocol documentation, and third-party GUIs are kept together so you can build, flash, and evolve the project starting from a single source of truth.
| Enclosure render (outside) | Enclosure render (inside) |
|---|---|
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| PCB Layout | PCB 3D View |
|---|---|
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| 3D printed enclosure (top view) | 3D printed enclosure (sockets visible) |
|---|---|
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If you want to build the project yourself, the step-by-step approach is:
Disclaimer: the JLCPCB link above is a referral URL, I get a little kickback if you use it to subscribe or buy from them. Thanks for your support!
-FULL image (using esptool). Prebuilt binaries and usage instructions for esptool are in the dist section.If you want to flash a different firmware, or update/reflash the core firmware in the future, there is no need to disassemble the board to access the native MCU USB port. Just use the isolated USB port with the included flash tool, and reflash the board using a -OTA image. OPSUM's main firmware OTA image is packaged under dist as well.
This repository includes everything, ranging from the basic OPSUM GUI plus third-party client-side tools that support the Core firmware communication protocol, to enclosure CAD models, PCB layout design files, assembly guides and protocol specification documentation.
You are free to use whichever compatible client (or firmware) matches your needs.
| Folder | Contents |
|---|---|
| dist/ | release binaries + compilation and flash instructions |
| protocol-specs/ | DFU (flashing) and UART (runtime communication with the host) protocol specs |
| src/Firmware/ | Core (main) and DFU (flash update mode) firmware source code |
| src/GUI/ | host-side GUI tools source code root folder |
| src/GUI/flash-tool/ | desktop DFU flashing GUI source code |
| src/GUI/opsum-gui/ | minimal OPSUM runtime GUI frontend source code |
| third_party_tools/ | bundled alternative host-side tools and board-side firmware binaries |
| hardware/ | schematic, PCB layout, BOM, CPL, Gerbers and manufacturing guide |
| enclosure/ | CAD files for the OPSUM case |
| howto-build/ | Manual assembly and soldering step-by-step instructions for the OPSUM board project |
OPSUM is inteded as an open, community driven project. Anyone is welcome to contribute to it by creating or improving client-side tools, firmware, enclosure, PCB design, protocol specs or documentation!
This project was born out of the desire to improve my PCB design skills, and to document a complete DIY approach to getting a full featured ammeter from scratch, instead of buying one.
In this endeavor, I've received a lot of precious support and ideas from the JFIXX community. If you want to join us to say hello, his discord server is a welcoming and friendly place, full of very skilled and amazing techs!
If you like this project and want to support it, you can do so by clicking the button below. Thank you! <3
| Qty | Value | Footprint | References |
|---|---|---|---|
| 9 | 100n | Capacitor_SMD:C_0603_1608Metric | C2, C3, C4, C5, C6, C7, C8, C9, C10 |
| 4 | 47u | Capacitor_SMD:C_1206_3216Metric | C12, C13, C14, C15 |
| 4 | 5K1 | Resistor_SMD:R_0603_1608Metric | R1, R2, R11, R12 |
| 4 | MountingHole_Pad | MountingHole:MountingHole_2.7mm_M2.5_Pad_Via | MH1, MH2, MH3, MH4 |
| 3 | 10K | Resistor_SMD:R_0402_1005Metric | R3, R4, R8 |
| 3 | Fiducial | Fiducial:Fiducial_1mm_Mask2mm | FID1, FID2, FID3 |
| 2 | 10R | Resistor_SMD:R_0402_1005Metric | R6, R7 |
| 2 | 10u | Capacitor_SMD:C_1206_3216Metric | C1, C11 |
| 2 | 2K2 | Resistor_SMD:R_0603_1608Metric | R13, R14 |
| 2 | GREEN | LED_SMD:LED_0805_2012Metric | LED1, LED2 |
| 2 | SS14 | Diode_SMD:D_SMA | D1, D3 |
| 1 | 100K | Resistor_SMD:R_0402_1005Metric | R10 |
| 1 | 330R | Resistor_SMD:R_0402_1005Metric | R9 |
| 1 | 3mR | WSL3637:WSL3637_VIS | R5 |
| 1 | ADuM1201AR | Package_SO:SOIC-8_3.9x4.9mm_P1.27mm | U2 |
| 1 | B0505S-2WR3 | B_S-2WR2_MNS:B_S-2WR2_MNS | PS1 |
| 1 | CH340N | Package_SO:JEITA_SOIC-8_3.9x4.9mm_P1.27mm | U1 |
| 1 | DPDT | EasyEDA_Lib:SW-TH_SK22D02G5 | SW1 |
| 1 | ESP32-S3-ZERO | ESP32-S3-ZERO:MODULE_ESP32-S3-ZERO | U3 |
| 1 | HL2309 | Package_TO_SOT_SMD:SOT-23-3 | Q1 |
| 1 | INA226 | Package_SO:TSSOP-10_3x3mm_P0.5mm | U4 |
| 1 | KH-TYPE-C-16P | KH-TYPE-C-16P:KINGHELM_KH-TYPE-C-16P | J1 |
| 1 | MMSZ5242B | Diode_SMD:D_SOD-123 | D4 |
| 1 | PANEL_DISPLAY_I2C | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J6 |
| 1 | SMAJ36A | Diode_SMD:D_SMA | D2 |
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It measures 80 × 50 mm and has 2 copper layers, 1.6 mm thick.
51 parts, built around the B0505S-2WR3, ADUM1201ARZ-RL7, CH340N and INA226AIDGSR. 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 nitefood/opsum repository on GitHub, at the commit this page was made from: the board is hardware/KiCad/Open_PSU_Meter_ESP32.kicad_pcb and its schematic hardware/KiCad/Open_PSU_Meter_ESP32.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).