DLR PST Sim ⚡🔄

Embedded transformer tap control on ESP32-C3 using Embassy async runtime. Subscribes to DLR ratings over MQTT, actuates relays to switch transformer taps, publishes output state.

Pre-requisites

• rust 1.93+
• probe-rs (cargo install probe-rs-tools)
• ESP32-C3 development board
• 4-channel relay module
• Multi-tap transformer

Hardware

Component	Purpose	Interface
ESP32-C3	Microcontroller	WiFi + MQTT
4-Channel Relay	Tap switching	GPIO
Multi-tap Transformer	Voltage adjustment	AC

Pinout

flowchart LR
classDef default fill:transparent,stroke:#333

subgraph esp32_c3
  gpio2
  gpio3
  gpio4
  gpio5
  wifi
end

subgraph relay_module [4-channel relay]
  relay1
  relay2
  relay3
  relay4
end

subgraph transformer [multi-tap xfmr]
  tap1
  tap2
  tap3
  tap4
end

gpio2 --> relay1 --> tap1
gpio3 --> relay2 --> tap2
gpio4 --> relay3 --> tap3
gpio5 --> relay4 --> tap4

Loading

MQTT Topics

Per ems/topic_structure_adr.md. Payload is FloatSample {ts, value} unless noted.

Subscribed:

• sites/{site_id}/devices/{dlr_device_id}/measurements/dynamic_rating/amps
• sites/{site_id}/devices/{device_id}/commands/set/tap_position/none — EnumSample

Published:

• sites/{site_id}/devices/{device_id}/measurements/output_voltage/volts
• sites/{site_id}/devices/{device_id}/measurements/tap_position/none — EnumSample
• sites/{site_id}/devices/{device_id}/measurements/status/none — EnumSample, LWT-backed

Tap Control Logic

The transformer adjusts tap position based on the dynamic rating received from dlr-operating-envelope:

• Higher rating → lower tap (higher voltage)
• Lower rating → higher tap (lower voltage)
• Gradual adjustments to prevent voltage spikes

Project Structure

├── Cargo.toml                 # package, features, target config
├── rust-toolchain.toml        # pinned 1.93.0
├── build.rs                   # compile-time cfg.yml baking
├── cfg.yml                    # wifi_ssid, mqtt_host per env
├── .cargo/config.toml         # probe-rs runner + target
├── src/
│   ├── main.rs                # entry point
│   ├── app.rs                 # library — embassy tasks
│   ├── network.rs             # WiFi + embassy-net setup
│   ├── mqtt.rs                # MQTT pub/sub client
│   ├── config.rs              # cfg.yml loader
│   ├── relay/
│   │   ├── mod.rs
│   │   ├── relay_driver.rs    # GPIO actuation
│   │   ├── relay_client.rs    # high-level relay API
│   │   └── relay_client_test.rs
│   └── transformer/
│       ├── mod.rs
│       ├── transformer_driver.rs    # tap position state machine
│       ├── transformer_client.rs    # high-level tap control
│       └── transformer_client_test.rs
└── tests/
    ├── integration_test.rs    # on-device embedded-test suite
    ├── hil_test.rs            # flash firmware + verify MQTT round-trip
    └── fixtures/              # testcontainer helpers

Testing Strategy

1. Unit — *_test.rs colocated per module, run on host via cargo cmd unit
2. Integration — integration_test.rs runs on-device via embedded-test + probe-rs
3. Hardware-in-loop — hil_test.rs flashes firmware, starts a testcontainer MQTT broker, verifies the full subscribe/publish loop

Usage

# Build + flash firmware
cargo build --bin=dlr-pst-sim --release

# Run on-device integration tests
cargo cmd integration

# Run hardware-in-loop tests (requires device on USB + testcontainers)
cargo cmd hardware-in-loop

# Monitor RTT output
probe-rs attach --chip esp32c3