This guide explains how to adapt earlier MiniSS Mainboard revisions (RevA/RevB) for use with Raspberry Pi Compute Module 5 (CM5). Some steps also apply to CM4 Lite.
Disclaimer
These are hardware modifications that may void warranty and can damage your board if done improperly. Proceed at your own risk. Always verify voltages with a multimeter before powering the system.
| Symptom / Goal | Affected Revisions | Section | Risk |
|---|---|---|---|
| 5V power/voltage insufficient | RevA, RevB | Bypass on-board power switch | Medium |
| SD card not detected (Lite only) | RevA (very first batch) | SD power fix (RevA only) | Low |
Note on boot devices
Only Lite models (CM4 Lite / CM5 Lite) boot from SD card. Non-Lite models boot from on-board eMMC.
RevA
- RevA — early batch may require the SD power fix below.
RevB
- RevB / RevB2 — use the 5V bypass only if you encounter brown-outs or boot instability with CM5.
Some units require a more direct 5V path. This mod disables the on-board power-switch IC by cutting JP1 and shorting JP2, then adding a direct 5V jumper wire between the two pads shown in Step 2.
Tools: precision knife, soldering iron, flux, 22–20 AWG wire, multimeter.
-
Cut JP1 (open-circuit) and short JP2 (solder bridge).
This effectively bypasses the power-switch IC path.
-
Locate two 5V points to be connected. (refer to image below for exact pads) Verify both points read ~5.0 V relative to GND with the multimeter.
-
Add a 22 AWG or 20 AWG wire between the two 5V points.
Keep the wire short, avoid sharp bends, and provide strain relief.
-
Verification:
With power applied, confirm stable 5V at the destination pad under load; check that the board boots normally.
Note
After this change, 5V is effectively hard-wired across the path. Ensure upstream supply/USB path and protections are adequate for your use case.
This applies to the very first batch of RevA and primarily affects CM4 Lite (SD-boot). Some newer bootloaders changed SD power expectations. With older CM4 Lite bootloaders this wasn’t an issue, but newer bootloaders can expose SD power delivery quirks on the very first RevA batch. If your CM4 Lite still cannot detect the SD card, supply SD power via the following modification.
If there is no 3.3 V on Pin 2 of the SD power header, you can bridge Pin 1 (3.3 V source) to Pin 2 (SD power rail) to supply SD power directly. This effectively bypasses the board’s SD power switch control
Steps:
- Power off the board.
- Measure Pin 2 (expected 3.3 V when enabled). If 0 V, proceed.
- Solder a short jumper from Pin 1 → Pin 2.
- Power on and verify:
- Confirm 3.3 V present on Pin 2.
- SD card is now detected by the bootloader/OS.
Reminder
Non-Lite Compute Modules boot from eMMC and will not use SD, so this fix is unnecessary for them.