Field Power And Connectivity Triager

Field Power And Connectivity Triager

Use this skill when the project works on the bench but breaks when powered the way it will be used in the real world.

Resources

• references/power-path-triage.md - USB vs VIN vs 3V3 diagnosis workflow
• references/wifi-and-peak-current.md - WiFi startup, brownout, and current-peak behavior
• references/measurement-checklist.md - what to measure before blaming the code
• ../../docs/board-support/uno-r4-family.md - Uno R4 family board caveats where relevant

When to Use

Use this skill when the request includes:

• "works on USB but not on my power supply"
• WiFi connects on the bench but not in deployment
• field-only resets, brownouts, or sensor instability
• suspected regulator or wiring-path weakness
• battery, VIN, or 3V3 supply-path questions

Workflow

1. Reproduce the split:

• USB works
• intended power path fails

2. Open references/power-path-triage.md to classify the supply path. 3. If WiFi or radio startup is involved, open references/wifi-and-peak-current.md. 4. Capture actual measurements from references/measurement-checklist.md before assuming the failure is in user code. 5. If the target is Uno R4 WiFi, open ../../docs/board-support/uno-r4-family.md and keep the connectivity-side hardware split explicit.

Core Rules

• "Works on USB" is evidence about the power path, not proof the code is sound.
• WiFi startup current peaks are first-class suspects on ESP32-class boards.
• Diagnose the supply path before tuning network code blindly.
• Treat sensor instability under field power as a possible power-integrity issue

until measurements say otherwise.

Verification

• Confirm the failure reproduces only on the intended power path.
• Confirm voltage and current conditions during the failing phase, not only at

idle.

• Confirm whether the failure happens at boot, during WiFi association, or later

under load.

• Confirm whether the same sketch behaves consistently once the power path is

corrected.

Integration

• Pair with power-budget-calculator when the issue may be under-sized source

capacity.

• Pair with ota-deployment-guardian when OTA fails only under field power.
• Pair with circuit-debugger when the board wiring itself is suspect.

Measurement Checklist

Use this reference before concluding the problem is in firmware.

Capture These Measurements

• source voltage
• board input voltage
• 3V3 rail voltage
• whether voltage changes during WiFi start or peripheral activity
• whether the board resets, hangs, or simply loses connectivity

Evidence To Keep

• exact power source used
• exact connection point used on the board
• whether peripherals share the same source
• whether the behavior changes after warm-up

Decision Hint

If the sketch is identical and only the power path changes, power integrity deserves priority over code changes.

Power Path Triage

Use this reference to classify the real supply path before deeper debugging.

Identify The Path

• USB port
• VIN pin
• regulated 3V3 input
• battery plus onboard regulation
• external regulator feeding peripherals and board together

Each path has different risk points.

Common Failure Shapes

USB Works, VIN Fails

Possible causes:

• weak external source
• wrong VIN voltage
• poor wiring path
• regulator headroom or heat issues

USB Works, 3V3 Injection Fails

Possible causes:

• bypassing the board's intended regulation path
• unstable external 3V3 rail
• insufficient transient response

Sensors Drift Only Off USB

Possible causes:

• noisier supply
• grounding differences
• regulator interaction with analog front ends

First Measurements

• supply voltage at source
• voltage at board input during load
• voltage at 3V3 rail during radio or sensor activity
• whether the board resets or just fails to connect

WiFi And Peak Current

Use this reference when WiFi or radio behavior changes across power paths.

Failure Pattern

Common report:

• board connects over USB
• board fails to connect or reboots on intended supply

That pattern often points to transient current demand or supply integrity, not to SSID or password bugs.

What To Check

• quality of the USB cable or alternate wiring path
• source current capability
• regulator transient behavior
• boot-time voltage sag during WiFi association

Useful Questions

• does failure happen before IP assignment?
• does serial output suggest brownout or reboot?
• does the board remain alive but disconnected, or does it restart?
• is the problem worse with peripherals active?

Practical Guidance

• reduce variables: test the same sketch on both paths
• avoid assuming a bench supply setting means the board actually sees that

voltage under load

• remember that ESP32-class boards can have sharper current peaks than simpler

MCU boards