Prototyping

Test Points and Solder Jumpers

Test Points

A test point is a dedicated, accessible node placed on the board purely to make verification easier. During bring-up you will probe nets with a multimeter, an oscilloscope, or a logic analyser. Without deliberate test point placement, you end up probing IC pins or via holes, which is frustrating, inaccurate, and slow.

KiCad provides test point schematic symbols with associated footprints. The most practical type for hand-assembled boards is the beaded loop, a small through-hole loop that accepts a multimeter probe or oscilloscope hook clip without slipping. SMT pad test points also work well with pogo pin fixtures for batch testing.

Place test points at every node that matters during commissioning:

• Power rails — add test points on each regulated supply (e.g. 12 V input after the polarity protection diode, 5 V output of U1). Verify these before populating anything downstream.
• Ground reference — a dedicated GND test point saves time when you need a probe ground clip. Place it near the power supply section.
• Signal outputs and control lines — comparator outputs, gate drive signals, and any net you expect to toggle during bring-up. Probing these without a breakout cable is worth the board area.

Label test points clearly on the silkscreen: TP1: 12V, TP2: 5V, TP3: GND, and so on. Your commissioning procedure can then refer to them explicitly: apply power, measure TP1 for 12 V, measure TP2 for 5 V, then proceed. This staged approach catches power supply faults before they damage downstream components.

Solder Jumpers

A solder jumper is a small pad footprint placed in series with, or bridging across, a net. It lets you make configuration decisions after the board is assembled, without cutting traces or adding wire. Used well, solder jumpers let the same board be tested in multiple configurations, extending the useful life of a prototype.

Jumpers come in two default states:

• Normally closed (NC) — the two pads are bridged by a thin copper web under soldermask. To break the connection, score through the web with a knife. To restore it, bridge the pads with solder.
• Normally open (NO) — the two pads are separated. Close the connection by bridging them with a blob of solder.

Three-pad variants act as a 1P2T switch, letting you route a signal to one of two destinations by selecting which pair of pads to bridge.

A common application is disabling a peripheral. If the LED connected to a GPIO pin is not needed in a particular test configuration, place an NC solder jumper in series with D1. During development the LED is active; cutting the jumper disables it without a board respin. A silkscreen callout such as cut to disable LED makes the intent clear to anyone working on the board later.

Solder jumpers can carry firmware configuration too. A GPIO sampled at startup, with one end of a jumper tied to that pin and the other tied to GND or VCC, gives a hard-wired setting that software cannot accidentally change. This suits node address selection or mode settings that are intended to be set once.

The alternative for configuration is a 0-ohm resistor in a standard 0402 or 0603 footprint. It achieves the same result, is easier to assemble in volume, and leaves pads accessible for measurement. Use whichever fits your assembly process.

Bodges, Trace Cutting and Jumper Wires

Bodges, Trace Cutting, and Jumper Wires

A bodge is a deliberate post-assembly modification to correct a routing error or trial a circuit change without ordering a new board. For a single-net change, a clean bodge is faster than a respin.

The standard bodge workflow:

• Identify the net. Trace the connection from source to destination on the schematic, then locate the corresponding trace on the board.
• Cut the trace. Score through the copper with a sharp knife, perpendicular to the trace direction. Make two cuts a millimetre apart and lift the copper section between them. Two cuts give a cleaner break than a single scrape.
• Verify isolation. Set your multimeter to continuity mode and confirm there is no connection across the cut. An incomplete cut will pass current and the modification will not work. Do not proceed without a passing continuity check.
• Bridge with wire. Route a fine wire (30 AWG wire-wrap or stripped magnet wire) from the source pad to the new destination, soldering each end. If the wire must cross other traces, use insulated wire or sleeve it with heat-shrink.

Keep bodge wires short and tack them down with kapton tape if they are likely to flex during use. Document every bodge with a photo and a note in your design log. If the change proves correct, incorporate it into the next board revision so the fix is permanent.