Extend AeroAlign with mixed CoG planning and telemetry base

2026-03-11 23:14:33 +01:00
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+# SkyLogic AeroAlign - CoG Scale Wiring
+
+**Version**: 0.1.0  
+**Date**: 2026-03-11  
+**Scope**: planned CoG scale node that shares the same Master and ESP-NOW fabric
+
+## Overview
+
+The CoG extension is based on two supports:
+
+- front support load cell
+- rear support load cell
+
+The recommended first implementation uses:
+
+- `1x ESP32-C3` or `1x ESP32-S3`
+- `2x HX711`
+- `2x single-point load cells` or your existing suitable load cells
+
+One HX711 per support keeps calibration and diagnostics simple.
+
+## Functional Model
+
+The CoG node reports three live values to the Master:
+
+- `front_weight_g`
+- `rear_weight_g`
+- `cog_position_mm`
+
+These values already fit the shared telemetry packet used by the current Master firmware.
+
+## Recommended Electronics
+
+| Part | Qty | Notes |
+|------|-----|-------|
+| ESP32-C3 or ESP32-S3 | 1 | same ecosystem as AeroAlign |
+| HX711 amplifier | 2 | one per support |
+| Load cell | 2 | typically 3 kg to 10 kg depending on model size |
+| LiPo or bench supply | 1 | portable or fixed jig |
+| TP4056 + regulator | optional | only for portable scale |
+
+## Wiring Strategy
+
+### HX711 #1: Front support
+
+| HX711 pin | Connection |
+|-----------|------------|
+| `VCC` | `3V3` |
+| `GND` | `GND` |
+| `DT` | `GPIO6` |
+| `SCK` | `GPIO7` |
+
+### HX711 #2: Rear support
+
+| HX711 pin | Connection |
+|-----------|------------|
+| `VCC` | `3V3` |
+| `GND` | `GND` |
+| `DT` | `GPIO8` |
+| `SCK` | `GPIO9` |
+
+These GPIOs are recommendations for the future CoG firmware. They are not yet hard-coded in the repo.
+
+## Load Cell Wiring
+
+Most 4-wire load cells expose:
+
+| Wire | Meaning |
+|------|---------|
+| Red | `E+` |
+| Black | `E-` |
+| Green | `A+` |
+| White | `A-` |
+
+Connect each load cell directly to one HX711.
+
+### Important
+
+Wire colors are not universal. Validate your load cells with the supplier datasheet or a multimeter before soldering.
+
+## Mechanical Layout
+
+```
+aircraft
+  |
+  +--> front support --> load cell #1 --> HX711 #1
+  |
+  +--> rear support  --> load cell #2 --> HX711 #2
+```
+
+The support spacing `L` must be known and entered into the system profile.
+
+## CoG Formula
+
+With front support at `x = 0` and rear support at `x = L`:
+
+`x_cog_from_front_support = rear_weight / (front_weight + rear_weight) * L`
+
+If you measure relative to the wing leading edge:
+
+`x_cog_from_leading_edge = support_offset_from_leading_edge + x_cog_from_front_support`
+
+## Calibration Plan
+
+Each support needs:
+
+1. zero / tare
+2. scale factor from known weight
+
+Recommended workflow:
+
+1. tare both supports empty
+2. place known weight on front support only
+3. save front factor
+4. repeat for rear support
+5. validate with known total weight centered between supports
+
+## Current Repo Status
+
+- shared protocol support exists in [telemetry_protocol.h](/Users/florianklaner/Github/AeroAlign/firmware/common/telemetry_protocol.h)
+- Master can already display CoG-style nodes in the existing UI
+- dedicated HX711 firmware is not implemented yet
+
+## Next Firmware Target
+
+Create a new node type, likely `firmware/cog_slave`, with:
+
+- HX711 reading
+- tare and scale calibration
+- CoG computation
+- ESP-NOW transmission using `DEVICE_TYPE_COG_SCALE`