# koheron-esp32-bridge

ESP32 firmware that bridges the **Butterfly EDFA Rack** — a 1550 nm MOPA: a [Koheron CTL200](https://www.koheron.com/photonics/ctl200-digital-laser-controller/) driving a DFB seed into an Agiltron M511 EYDFA power amplifier (output up to ~1 W / 30 dBm) — to WiFi/MQTT for monitoring and control from Home Assistant (broker `192.168.0.102:1883`, anonymous).

The whole rack is presented as a **single HA device** (`butterfly_edfa_rack`). Topics, mirroring the lab's EDFA→MQTT convention:

```
lab/laser/butterfly_edfa_rack/availability      online | offline (LWT)
lab/laser/butterfly_edfa_rack/diag/<key>        ESP/network diagnostics
lab/laser/butterfly_edfa_rack/seed/<key>        Koheron CTL200      (increment 3)
lab/laser/butterfly_edfa_rack/amp/<key>         Agiltron M511       (increment 4)
lab/laser/butterfly_edfa_rack/set/<...>         commands            (increment 5)
```
HA discovery configs are published under `homeassistant/...`, all sharing one `device` block so entities group under the single rack device.

## Optical architecture

The rack is a **MOPA** (master-oscillator power-amplifier) at 1550 nm:

```
 Koheron CTL200            Agiltron M511 EYDFA (two-stage)
 ┌──────────────┐          ┌─────────────────────────────────────┐
 │ DFB1550LP    │  fibre   │  pre-amp stage  ──►  booster stage   │  fibre
 │ seed diode   ├─────────►│  (pump diode A)      (pump diode B,  ├────────►  output
 │ + TEC        │          │   ~170 mA, ~16 dBm    "pump-1")      │           (up to ~1 W
 └──────────────┘          └─────────────────────────────────────┘            / 30 dBm)
   ilaser, lason             input PD   preamp PD     output-1 PD
```

**The M511 has two internal pump diodes**, and the firmware reads both:

- **Pre-amp pump** — runs semi-independently at ~170 mA, lifts the seed to ~16 dBm (`amp/preamp_current_ma`, `amp/preamp_power_dbm`).
- **Booster pump = "pump-1"** — the controllable output stage (`amp/pump1_current_ma`, set via `set/amp/pump1_current_ma`).
- **"Pump-2"** is a second booster channel that this unit leaves at 0 mA regardless of settings (per `Lab/Equipment/Lasers/Agiltron EDFA`); we don't drive it. It is read but not exposed as a control.

Run the booster in **ACC (constant-current)** mode — APC stepping quantises the output. Below transparency the booster erbium fibre *absorbs* the pre-amp output, so output stays at the PD floor (−60 dBm) until the pump is high enough.

### Pump-1 vs output characterisation (2026-06-17)

Two sweeps. The transparency sweep used ~6 mW (7.8 dBm) seed into the EDFA; the high-power sweep added a 3 dB pad (input 3.2 dBm, within the ≤5 dBm benchtop spec) and a direct output-to-power-meter connection.

| Pump-1 | Output-1 (internal PD) | note |
|-------:|------------------------|------|
| 500–900 mA | −60 dBm | below transparency, signal absorbed |
| 1200 mA | 21.0 dBm | booster turns on |
| 1500 mA | 23.1 dBm | |
| 2000 mA | 25.9 dBm | |
| 2500 mA | 27.1 dBm / 514 mW | documented 0.5 W operating point |
| 3000 mA | 28.3 dBm / 679 mW | |
| 3500 mA | 29.3 dBm / 857 mW | |
| 4000 mA | 30.1 dBm / 1026 mW | **1 W rated ceiling** |
| 4500 mA | 30.85 dBm / 1216 mW | over-rating; curve still ~linear (not saturated) |

The unit (factory APC setpoint 30 dBm) comfortably exceeds 1 W: 1.22 W at 4500 mA with the output still climbing ~0.74 dB/500 mA and module temp only ~30 °C — so its true saturated maximum is higher, but driving a 1 W-rated pump diode past rating trades lifetime for diminishing return. Pump current overshoots ~2× briefly on each step up and settles in 2–4 s, so **ramp gradually** rather than jumping to the setpoint.

> **Internal PD vs external power meter:** at 4500 mA the internal PD reported 1.22 W while a Thorlabs meter measured **1.05 W** at the output (~0.6 dB high / residual loss). Treat the `amp/output*_power_dbm` telemetry as indicative, ~0.5–0.6 dB optimistic, not a calibrated power reading. (The earlier lab notes saw the opposite sign through a different connection, so the offset is path-dependent.)

> **Safety:** Class 4, >1 W, invisible 1550 nm. The firmware clamps pump-1 to a soft 4000 mA ceiling (≈ the 1 W rating, `PUMP_CURRENT_SOFT_MAX_MA`), liftable to the 8000 mA hard protocol max (`PUMP_CURRENT_HARD_MAX_MA`) only while the Pump Limit Override switch is on, and seed current to `SEED_CURRENT_MAX_MA` — guardrails against accidental over-drive, **not interlocks**. Above 1 W the Agiltron manual requires matched high-power connectors or a splice on the output, else the output fibre/amplifier can be damaged. Always drop the pump to 0 before unmating any fibre. Treat the output as hazardous unless it terminates in a power meter / beam dump.

## Hardware

Full parts list (seed, amplifier, supplies, fibre, wiring) is in [`BOM.md`](BOM.md).

- ESP32-D0WD-V3 dev board (WROOM-32 class), CP2102N USB bridge → `/dev/ttyUSB0`, MAC `b0:cb:d8:8f:ba:10`.
- The ESP32 USB port is used **only** for flashing/console (UART0).
- Two instrument links on separate hardware UARTs:

  | ESP32          | Instrument                          | Protocol |
  |----------------|-------------------------------------|----------|
  | GPIO17 (TX2) → | Koheron CTL200 RX (terminal block)  | ASCII, 115200 8N1, `\r\n`, `>>` prompt |
  | GPIO16 (RX2) ← | Koheron CTL200 TX                   | |
  | GPIO26 (TX1) → | Agiltron M511 RX (P2 pin 3)         | binary 0x55AA packets, 115200 8N1 |
  | GPIO25 (RX1) ← | Agiltron M511 TX (P2 pin 7)         | |
  | GND            | both grounds                        | |

  All links are 3V3 logic (CTL200 is 5V-tolerant). UART1 is remapped off its default flash-clashing pins.

> **Network:** the firmware pins a static IP `192.168.0.150` (gateway `.1`, /24) — see `USE_STATIC_IP` in `include/config.h`. This avoids the clash with the BKtel EDFA Pi on `.101` that a DHCP lease originally caused. `.150` is outside any device documented in the HA notes; move it if your DHCP pool overlaps.

## Toolchain

PlatformIO (Arduino framework), pinned in a project-local `.venv` so nothing is installed globally.

```bash
make            # show targets
make build      # compile
make upload     # compile + flash (PORT=/dev/ttyUSB0 by default)
make monitor    # serial console at 115200
make detect     # identify the chip on the port
```

A fresh checkout self-bootstraps the venv on first `make`.

## Configuration

Copy `include/secrets.example.h` → `include/secrets.h` (git-ignored) and fill in WiFi + MQTT details. Needed from increment 2 onward.

## Increment roadmap

- [x] **1 — toolchain check.** Blink + serial heartbeat; confirms build/upload/monitor.
- [x] **2 — WiFi + MQTT + HA discovery.** Joins WiFi, connects to broker with an LWT availability topic, publishes diagnostic entities (uptime, RSSI, IP).
- [x] **3 — Seed telemetry (read-only).** UART2 → Koheron `lason`/`ilaser`/`vlaser`/`rtset`/`rtact`/`itec`/`vtec`/`tboard`/`iphd`/`err`; published under `seed/...` as HA sensors. Verified live against CTL200 fw v0.21 (echo + value + `>>` framing, parsed correctly).
- [x] **4 — Amp telemetry (read-only).** UART1 → Agiltron `get_status` (binary 0x55AA, ported from `edfa.py`); publishes module/pre-amp temp, pre-amp & pump-1 currents, input/pre-amp/output dBm, warnings under `amp/...`. Verified against the live unit (SN Y4022708, PN EDFA-1C51113331111, device ID 0x0000006F). `amp/pump_enabled` reads the authoritative `get_settings` field.
- [x] **5 — control.** `set/...` for seed (`lason`, `ilaser`) and amp (pump on/off, pump-1 ACC current) as HA switch/number entities, with firmware current clamps. Verified end-to-end: MQTT command → seed lasing → booster ramp to 27 dBm. Seed TEC setpoint (`rtset`, in ohms) is also settable, with a read-only °C readout derived from the thermistor. A **Pump Limit Override** switch (`set/amp/pump_override`) lifts the pump-1 clamp from the soft 4000 mA (1 W) guardrail to the 8000 mA protocol max for supervised over-rating; it defaults off on every boot and re-clamps a running pump back to 4000 mA when switched off. (Future: seed `tecon`, amp APC power, Koheron `save`.)

## MQTT interface

State topics retained under `lab/laser/butterfly_edfa_rack/`:

| Topic suffix | Meaning |
|--------------|---------|
| `availability` | `online` / `offline` (LWT) |
| `diag/{uptime,rssi,ip}` | ESP / network diagnostics |
| `seed/link` | Koheron reachable? |
| `seed/laser_enabled` | seed laser on (1/0) |
| `seed/current_ma`, `seed/voltage_v` | seed drive |
| `seed/rt_setpoint_ohm`, `seed/rt_actual_ohm` | thermistor setpoint / actual |
| `seed/temp_c` | seed diode temperature (from `rt_actual` via NTC β-model, indicative) |
| `seed/tec_current_a`, `seed/tec_voltage_v`, `seed/board_temp_c` | seed TEC / board |
| `seed/photodiode_ma`, `seed/error` | seed monitor PD, CTL200 error code |
| `amp/link` | Agiltron reachable? |
| `amp/module_temp_c`, `amp/preamp_temp_c` | EDFA temperatures |
| `amp/preamp_current_ma`, `amp/preamp_power_dbm` | pre-amp stage |
| `amp/pump1_current_ma`, `amp/pump1_set_ma` | booster pump actual / setpoint |
| `amp/input_power_dbm`, `amp/output1_power_dbm`, `amp/output2_power_dbm` | optical powers |
| `amp/pump_enabled`, `amp/warnings` | booster state, decoded warnings |
| `amp/pump_override` | pump-1 limit override on (1/0) |

Command topics (publish to `lab/laser/butterfly_edfa_rack/set/`):

| Topic suffix | Payload | Action |
|--------------|---------|--------|
| `seed/laser` | `1` / `0` | Koheron `lason` |
| `seed/current_ma` | mA | Koheron `ilaser` (clamped ≤ `SEED_CURRENT_MAX_MA`) |
| `seed/rt_setpoint_ohm` | Ω | Koheron `rtset`, seed TEC setpoint (clamped `SEED_RT_SETPOINT_MIN/MAX_OHM`) |
| `amp/pump` | `1` / `0` | Agiltron pump on / off |
| `amp/pump1_current_ma` | mA | set ACC mode + pump-1 current (clamped ≤ soft 4000 mA, or ≤ hard 8000 mA when override on) |
| `amp/pump_override` | `1` / `0` | lift the pump-1 clamp from soft (4000 mA / 1 W) to hard (8000 mA). Default off; switching off re-clamps a running pump to soft |