# Calarin prototype purchasing checklist — 2026-04-12

## Assumption
This checklist assumes:
- first PCB run = 5 units
- we want enough parts to assemble 5 boards without getting bricked by one dead module, one lifted pad, or one stupid shipping mistake

So the rule is:
- buy exact-ish quantities for cheap passives
- buy spares for anything painful, slow, or easy to kill

## Tier 1 — buy now, no debate
These are already supported by the clean schematic direction.

### Batteries
- 302540 LiPo, primary direction: buy 4 units
  - preferred source: Ecocell 302540
- 402030 LiPo, bring-up hedge: buy 2 units
  - preferred source: PMD Way 402030

Why:
- 302540 is the real product-direction battery
- 402030 prevents battery sourcing from blocking electronics bring-up

### Core silicon / critical parts
- ESP32-S3-WROOM-1 module: buy 8
- MSM261DGT003 microphone: buy 10
- W25Q128JVSIQ flash: buy 10
- IP5306-I2C: buy 10
- ME6210A33M3G LDO: buy 10

Why these counts:
- 5 needed for boards
- 3–5 extra protects against assembly loss, DOA parts, and one re-spin-level mistake without reordering everything

### Connectors / electromechanical
- USB-C connector (chosen schematic footprint family): buy 10
- tactile switch (chosen schematic footprint family): buy 15
- LED part used in schematic / chosen LED equivalent: buy 15
- programming/header connectors: buy 10 sets
- battery JST mating headers / cable adapters as needed: buy 10

Why:
- these are easy to damage mechanically
- spares are cheap insurance

## Tier 2 — buy in reels / strips / practical excess
### Passives
For the full passives set represented in the schematic:
- resistors: buy at least 20 of each value used
- capacitors: buy at least 20 of each value used
- pull-ups / dividers / decouplers: do not try to optimize this to the bone

Practical rule:
- if sourcing from DigiKey/Mouser/LCSC, just buy 20–50 of each value used
- for tiny 0402/0603 passives, err on the side of more, not less

Why:
- passives are the dumbest possible place to get blocked

## Tier 3 — prototype assembly support stuff
These are not the board BOM, but they matter if we want to actually build.

- solder paste / flux / wick / spare stencil path
- USB-C cables for power/programming
- at least 2 good bench battery leads / JST adapters
- enclosure prototype materials if doing immediate physical fit checks
- MagSafe magnet/ring samples for fit testing: buy 5–10 sample pieces

## Exact recommended first order
### Order A — immediately
- 4x Ecocell 302540
- 2x PMD 402030
- 8x ESP32-S3-WROOM-1
- 10x MSM261DGT003
- 10x W25Q128JVSIQ
- 10x IP5306-I2C
- 10x ME6210A33M3G
- 10x USB-C connectors
- 15x tactile switches
- 15x LEDs
- 10x programming/header sets
- 20–50x each passive value used in schematic

### Order B — if we want more battery certainty
- 4x 99Tech 302540 as secondary retail-source hedge

### Order C — only if retail battery path gets annoying
- LP302540 vendor/custom order inquiry
  - use if we need custom wire length / connector / more stable medium-run supply

## Hard rules
- Do not wait for the perfect battery before ordering the rest.
- Do not let the 402030 fallback become the product-shape anchor.
- Do not under-order the ESP32 modules or microphones.
- Do not buy exactly 5 of anything expensive-and-fragile and then act surprised.

## Decision-ready summary
If we want one clean purchasing move this week:
1. place the board-parts order
2. buy Ecocell 302540 packs
3. buy a couple PMD 402030 packs
4. move forward with prototype fit + bring-up in parallel

That is the fastest sane path.