Goal: build the first version of hydraamulet, a wearable control device for the Hydra.
Hardware (decided 2026-09-11):
- Buy the Waveshare ESP32-S3-Touch-LCD-1.85: round 1.85 inch capacitive touch LCD (360x360, ST77916 + CST816S), ESP32-S3R8 (8MB PSRAM, 16MB flash), dual microphone array (noise/echo suppression, voice recognition and wake word), QMI8658 6-axis IMU, 3.7V Li battery header, USB-C.
- BUY LINK: https://www.amazon.com.be/dp/B0H2GVN7F5 for 48.99 EUR. Variant in the CNC-milled aluminium case, the most amulet-shaped option. No battery included; order a 3.7V MX1.25 cell with it. Listing does not mention a speaker, so plan on display plus buzzerless feedback for v1.
- Chosen over the ESP32-S3-Touch-LCD-1.28 and the M5Stack Dial because neither has a microphone. The mic enables voice steering on the amulet, in line with Hydra Commander.
- Docs: https://www.waveshare.com/wiki/ESP32-S3-Touch-LCD-1.85
Scope for v1:
- Connect the amulet to the Hydra over radio: Bluetooth (BLE) or WiFi. Decide which link fits best (BLE to a nearby head or node, or WiFi straight onto the venue network / hydraneck).
- Send basic steering commands to the Hydra from the amulet (the minimal set that proves the control path end to end).
- Show connection state and the active command on the round display.
- Voice input via the onboard mics is the follow-up once the command path works.
Radio constraint:
- The ESP32-S3 radio is 2.4 GHz only. It does not support 5 GHz or 6E. All venues emit the SSID "experiencenet" on WiFi 6E, so the amulet cannot join it.
- WiFi plan: broadcast a second SSID "experiencenet_amulet" on 2.4 GHz from the hydraneck routers. Rollout tracked in #700.
- BLE remains the fallback if the 2.4 GHz SSID is not wanted, but needs a BLE-capable receiver near the operator.
Open questions:
- Which Hydra endpoint receives the commands (cluster API vs a node).
- Whether spoken feedback is wanted later (then add the 1.85C speaker variant or an external speaker).