Ad5254bo

AD5254 Quad-Digipot Breadboard Breakout

A custom breakout board that does what you were trying to build by hand (an AD5254 on a TSSOP adapter) — but designed to be factory-assembled by PCBWay so you never solder the fine-pitch chip, and shaped to plug into a breadboard like a fat DIP.

One board = 4 channels (the AD5254 is a quad digipot). Two boards (addresses 0x2C and 0x2D) = the full 8 channels on one I²C bus.

This is a logic-level, low-voltage board (3.3 V I²C). It carries no stim voltage — the wiper outputs run over to the daughtercards. So it's a simple, low-stakes first custom PCB.

STATUS: Gerbers generated & DRC-clean (2026-08-02)

Board laid out in KiCad 10 from generate.py, 0 DRC violations, 0 unconnected, rendered and visually verified. Ready to upload for a quote:

• ad5254-breakout-gerbers.zip — Gerbers + drill (drop into PCBWay/JLCPCB).
• ad5254bo.kicad_pcb — editable board. render-top.png / render-bottom.png.
• generate.py — the script that builds it (re-run to tweak).

What's on the board

• U1 — AD5254BRUZ100 (TSSOP-20), factory-soldered.
• C1 — 0.1 µF (0603): VDD decoupling, close to the chip.
• WP tied to VDD on-board (writes always enabled — avoids the write-protect gotcha).
• AD0, AD1 tied to GND on-board → I²C address 0x2C.
• Ground pours top + bottom, stitched.
• 2× 1×8 headers, 0.1" pitch, rows 0.6" apart so the board straddles a breadboard's center trench.
• I²C pull-ups: NOT on-board — by design. Pull-ups belong once on the shared bus, not per board (two of these boards on one bus would double them up). Add one 4.7 kΩ SDA→3V3 and one SCL→3V3 on the breadboard, as you already do.

Final board size: 20 × 24 mm, 2-layer.

Second board / address 0x2D

Both AD0 and AD1 are tied to GND (→ 0x2C). For the 0x2D board, edit generate.py (set pin 4 / AD0 to VDD instead of GND) and re-run — or add the solder-jumper option. Two boards (0x2C + 0x2D) give the full 8 channels.

Header pinout (16 pins broken out)

As actually built (verified against generate.py 2026-08-02). Pin 1 is the end marked by the square pad / silk triangle; the table runs pin 1 → pin 8.

For basic use you need VDD (J2.1), GND (J1.8), SDA (J1.7), SCL (J2.5), and the four wipers W0 (J1.1), W1 (J1.4), W2 (J2.6), W3 (J2.2).

Each channel exposes its wiper W, plus the A and B terminals, so it drops straight into the openEMSstim daughtercard network (which uses A + W as a rheostat). For simple use you only need VDD, GND, SDA, SCL, and the four W pins.

Board parameters (for a PCBWay quote)

• Size: ~23 mm × 18 mm (0.9" × 0.7")
• Layers: 2
• Thickness: 1.6 mm FR4
• Copper: 1 oz
• Min trace/space: 6/6 mil (well within standard, cheapest tier)
• Surface finish: HASL (cheapest) or ENIG
• Quantity: 5 (typical minimum) — you need 2, so you'll have spares

Plug those into PCBWay's instant quote for the bare-board price; add the BOM (bom.csv) + assembly for the assembled price. See "Getting a quote."

Address

To make the second board answer at 0x2D instead of 0x2C, the only change is AD0 → VDD instead of GND. Two clean ways:

• Order two board variants (trivial netlist change), or
• Add two solder-jumper pads (AD0/AD1 selectable GND vs VDD) so one board design covers both — recommended; costs nothing and keeps one design.

Getting a quote / to fab-ready files

1. Ballpark now: put the board parameters above into PCBWay's instant-quote calculator (bare board), and their assembly calculator with bom.csv for the assembled adder. That's your cost, today.
2. To actually order, PCBWay needs Gerbers + placement. That's a ~15-minute layout of this simple board in KiCad (free) from the netlist.txt here — I can walk you through it step by step, or PCBWay's own assembly/design service can lay it out from this spec. Either way the design is fully defined here; only the layout/export step remains.

Still required after assembly

A pre-assembled board removes the soldering, not the checks: probe it on the breadboard, run the firmware I²C scan (S command) to confirm it answers at its address, and read a wiper back (d) — same bring-up we did on the bench.