# Ordering & Assembly Guide

## JLCPCB Order Settings

Upload `baby-mobile-panel.kicad_pcb` gerbers with these options:

| Setting | Value |
|---|---|
| Layers | 2 |
| PCB Thickness | 1.6mm (carrier) / 0.8mm works too |
| Surface Finish | LeadFree HASL (cheapest) or ENIG |
| **Castellated Holes** | **Yes** (required for adapters) |
| **V-Score** | **Yes** (break between carrier and adapters) |
| Quantity | 5 (minimum) |
| **Estimated Cost** | **~$8 for 5 panels** |

If ordering JLC assembly (SMT), upload `carrier_bom_jlc.csv`.
Otherwise, hand-solder the carrier components yourself — everything
is 0805 or larger except the TPS61220 (SC-70-5, fine-pitch but doable
with flux and a fine tip).


## Carrier Board BOM

| Ref | Part | Package | LCSC | ~Cost | Notes |
|---|---|---|---|---|---|
| U1 | TPS61220DCKR | SC-70-5 | C83951 | $0.80 | **Pin 1 dot on silk** |
| U2 | IS25LP128F-JBLE | SOIC-8 | C194872 | $1.80 | **Pin 1 dot on silk** |
| L1 | 4.7µH inductor | 0805 | C408336 | $0.15 | |
| C1 | 10µF ceramic | 0805 | C15850 | $0.05 | Boost input |
| C2 | 10µF ceramic | 0805 | C15850 | $0.05 | Boost output |
| C3 | 100nF ceramic | 0805 | C49678 | $0.01 | Flash decoupling |
| C4 | 100nF ceramic | 0805 | C49678 | $0.01 | (optional XIAO decoupling) |
| C5 | 10nF ceramic | 0805 | C1710 | $0.01 | Audio LPF |
| R1 | 4.7KΩ | 0805 | C17673 | $0.01 | Audio LPF |
| R2 | 10KΩ | 0805 | C17414 | $0.01 | Flash CS pullup |
| J1 | JST SH 10-pin SMD | 1.0mm | C160404 | $0.30 | Right-angle |
| J2,J3 | Female header 1×7 | 2.54mm | C124378 | $0.20 | XIAO socket (×2) |
| — | Seeed XIAO nRF52840 | module | — | $9.90 | From Seeed/Amazon |
| | **Carrier subtotal** | | | **~$13.30** | |

### Not on PCB (buy separately)

| Item | Source | ~Cost |
|---|---|---|
| JST SH 10-pin cable (both ends female) | Amazon/AliExpress | $1.50 |
| 30AWG wire (for adapter-to-JST) | Amazon | $5/spool |
| 2×AA battery holder | Reuse from toy | $0 |


## Breakaway Adapter BOM

The adapters are **passive PCBs** — no components except one JST SH
connector each. Buy the connector that matches your adapter:

| Adapter | JST SH Pins | LCSC | ~Cost |
|---|---|---|---|
| SOP-8 | 8-pin | C160402 | $0.25 |
| SOP-16 narrow | 10-pin | C160404 | $0.30 |
| SOP-16 wide | 10-pin | C160404 | $0.30 |

You only need one adapter per toy — snap off the right one.


## Assembly Order

### 1. Carrier board (do this first, test before connecting to toy)

1. **Solder U1 (TPS61220)** — align pin 1 dot. Tin one pad, place
   chip, reflow that pad, then solder remaining 4 pins.
2. **Solder L1, C1, C2** — boost converter circuit. Apply 2×AA
   battery voltage to VBAT/GND test points. Measure 3V3 output —
   should read 3.30V ±0.1V.
3. **Solder U2 (IS25LP128F)** — align pin 1 dot. Same technique as U1.
4. **Solder C3, R2** — flash decoupling and CS pullup.
5. **Solder R1, C5** — audio RC filter.
6. **Solder J1 (JST SH)** — align pin 1 mark.
7. **Solder J2, J3** — XIAO female headers.
8. **Plug in XIAO** — USB-C faces the left edge marked on silk.
9. **Test** — upload pin_discovery.ino, verify serial output.

### 2. Adapter board

1. **Snap off** the adapter matching your toy's MCU package.
2. **Solder JST connector** to adapter's top surface.
3. **Desolder** original MCU from toy PCB (hot air or iron + flux).
4. **Place adapter** in empty footprint, pin 1 aligned.
5. **Solder castellated edges** — the half-holes sit on the SOP pads.
   Apply flux, touch with iron, solder wicks into the half-hole.
6. **Plug JST cable** from adapter into carrier J1.

### 3. Map and wire

1. Upload **pin_discovery.ino** to XIAO.
2. Use multimeter + the serial tool to identify each SOP pin's function.
3. Create your pin map (see BRAIN_TRANSPLANT.md).
4. Update **baby_mobile_v2.ino** pin definitions.
5. Upload final firmware.
6. Upload audio via USB mass storage.


## Silkscreen Guide

All polarized components have pin 1 dots (●) on the silkscreen:
- **U1 (TPS61220):** dot near pin 1 (VIN)
- **U2 (IS25LP128F):** dot near pin 1 (~CS)
- **J1 (JST SH):** dot near pin 1 (VBAT)
- **Each adapter:** dot near SOP pin 1

The XIAO outline shows the board rectangle with a USB-C bump
on the left edge. Pin labels (D0-D10, 3V3, GND, 5V) are printed
next to each header hole.