hw: receiver enclosure v2 from the first assembly

hardware/receiver/WIRING.md

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+# tinyDecoders receiver: wiring and assembly
+
+This is the **receiver** (433 MHz decoder with OLED, `tinyDecoders/`), not a tinySensor emitter. Emitter boards are documented in `hardware/tinysensor/`.
+
+- Firmware: `tinyDecoders`, env `promicro` (`pio run -d tinyDecoders -e promicro -t upload`)
+- Enclosure: `openscad/receiver.scad`, Orca project `openscad/print/receiver.3mf`
+- Boards: SparkFun-style Pro Micro 5 V / 16 MHz (ATmega32U4), RXB6 433 MHz superheterodyne receiver, 0.91" SSD1306 OLED 128×32 (I2C, 0x3C, onboard regulator)
+
+![Receiver wiring](wiring.svg)
+
+## Connections
+
+Every wire is **soldered at both ends** (no Dupont, no JST). Lengths include slack: cut on site.
+
+| From | To (Pro Micro) | Net | Colour | Ends | Length |
+|---|---|---|---|---|---|
+| RXB6 DATA (DATA end) | pin **4** (PD4 / ICP1) | radio data | green, 1 heat-shrink ring | soldered / soldered | 40 mm |
+| RXB6 +5V (DATA end) | VCC splice | VCC | red | soldered / soldered | 60 mm |
+| RXB6 GND (DATA end) | GND splice | GND | black | soldered / soldered | 40 mm |
+| OLED SDA | pin **2** (SDA) | I2C data | green | soldered / soldered | 70 mm |
+| OLED SCL | pin **3** (SCL) | I2C clock | yellow | soldered / soldered | 70 mm |
+| OLED VCC | VCC splice | VCC | red | soldered / soldered | 80 mm |
+| OLED GND | GND splice | GND | black | soldered / soldered | 70 mm |
+| Pro Micro **VCC** (right row) | VCC splice | VCC | red | soldered / soldered | 30 mm |
+| Pro Micro **GND** (right row, 2nd from USB) | GND splice | GND | black | soldered / soldered | 30 mm |
+| RXB6 ANT (ANT end) | helical antenna 27.5 × Ø5 mm | antenna | — | soldered | — |
+
+Parts on the wires:
+
+| Part | Value | Between | Where |
+|---|---|---|---|
+| R1 | 3.3 kΩ | SDA – VCC | in line, at the Pro Micro end, in the free zone in front of the RXB6 (validated on the bench: ~4.3 V high, ~160 ns rise) |
+| R2 | 3.3 kΩ | SCL – VCC | same |
+| C1 | 100 nF ceramic | RXB6 +5V – GND | soldered on the RXB6 DATA-end pin stubs |
+| C2 | 10 µF: ceramic (X5R/X7R), or tantalum 16 V (**+ on +5V**: a reversed tantalum fails short), or electrolytic laid flat | RXB6 +5V – GND | same, next to C1; a standing electrolytic (11 mm) would hit the antenna |
+| R3 (optional) | 10–47 Ω | in series in the RXB6 +5V, before C2 | RC filter against USB and OLED charge-pump noise |
+
+Not connected: RXB6 DER, the second +5V and both GND pins of the RXB6 ANT end, every other Pro Micro pin.
+
+## Pin positions in the enclosure
+
+Pro Micro top view, micro-USB against the rear wall, seen from the front of the box:
+
+| | Rear (USB) → front |
+|---|---|
+| Left row | TX0, RX1, GND, GND, **2**, **3**, **4**, 5, 6, 7, 8, 9 |
+| Right row | RAW, **GND**, RST, **VCC**, A3, A2, A1, A0, 15, 14, 16, 10 |
+
+The first pin (9 / 10) is 1.5 mm from the front edge. The RXB6 lies across the box, DATA end on the left (near pins 2–4), ANT end on the right. Its DATA end carries +5V, DER, DATA, GND, with +5V and GND on the outside: **read the silkscreen** to know which pin falls to the front once the board is flipped.
+
+## Space under the RXB6
+
+The RXB6 shield sits 1 mm above the Pro Micro components, 2.7 mm above its board. It covers the left-row pins 3, 2, GND, GND and the right-row VCC: their solder joints have about **1.9 mm** of headroom.
+
+- Solder the Pro Micro wires **before** fitting the RXB6, lying flat, leaving **sideways** (along X), never over the components.
+- Signal wires: thin wire, 30 AWG wire-wrap (28 AWG at most). Power: 26 AWG is plenty (tens of mA).
+- **One wire per pin** under the shield. Bring VCC out with a single red wire to a splice in the free zone in front of the RXB6 (above the front half of the Pro Micro), where the RXB6 +5V, the OLED VCC and R1/R2 join under heat-shrink. Take GND from the right-row GND next to RAW: it lies just behind the RXB6, not under the shield.
+- The shield is at GND: put a piece of Kapton tape under it.
+
+## Assembly order
+
+1. Pro Micro: solder SDA, SCL, DATA, VCC and GND wires flat, sideways. Plug its 8 mm header pins into the plate rails (the 1.2 mm holes print closed up: drill them to 0.8 mm).
+2. RXB6: cut the pins to 2–3 mm stubs, solder C1, C2 (and R3) on the DATA-end stubs, then the DATA, +5V, GND wires and the helical antenna on ANT. Kapton under the shield, flip the board onto its two supports (shield on the supports, ergots at its ends), drop of glue.
+3. OLED: glue it in the face pocket, pins on the left (text upright), solder SDA, SCL, VCC, GND.
+4. Make the VCC and GND splices with R1 and R2, heat-shrink.
+5. USB test before closing: the OLED shows "Waiting for data", then decoded sources; RFLink lines come out on the USB serial port at 57600 baud.
+6. Close the plate: 4 × M3×6 cylinder-head machine screws (pilot 2.5 mm, drill 2.8 mm if a screw binds).