hermes-bot/CONTEXT.md

Current state

Last updated 2026-10-04. HANDOFF.md is the brief; this file tracks where the work stands.

Hardware on hand

Raspberry Pi 4 (8 GB), BrainCraft HAT, Arducam UC-346 camera. Not yet: servos, USB-C splitter, printed enclosure, speakers. Work until those arrive is limited to what the Pi, HAT and camera can do.

The Pi (hermes-bot)

• Ubuntu 24.04.5 server, kernel 6.8.0-1065-raspi (fully upgraded), flashed from talos. User hermes (key-only; passwordless sudo), SSH keys for kyle@vade (talos) and kyle@straylight.
• On Wi-Fi at 192.168.88.152 (MAC d8:3a:dd:0d:66:f5); eth0 is not cabled. The owner says it has a static IP on the rack switch; that address is not recorded here yet. USB link: 10.55.0.2 (see package 0b below); ssh hermes@10.55.0.2 works from talos. avahi-daemon is installed, but mDNS is off in systemd-resolved on talos, so hermes-bot.local doesn't resolve there; use the IP.
• cloud-init applies network-config and user-data on the first boot only. To change Wi-Fi later, edit /etc/netplan/50-cloud-init.yaml on the Pi, or bump instance_id in meta-data on system-boot. pi/50-cloud-init.yaml is a template for the Wi-Fi block; it is gitignored because it holds credentials.
• Installed: ROS 2 Jazzy (ros-base, ros-dev-tools, colcon, robot_state_publisher, xacro, camera_ros); python3-numpy/pil/spidev/lgpio/rpi-lgpio; a venv ~/venv (system site packages visible) with adafruit-circuitpython-rgb-display and Blinka. Workspace: ~/ros_ws, source synced from ros/ with rsync -a --delete --exclude __pycache__ ros/ hermes@<ip>:~/ros_ws/src/, then colcon build --symlink-install.
• CPU governor is ondemand; at full clock the face costs about half as much CPU. Set performance in the installer (package 5). It is not persistent yet.

Package 0a (platform proof on Ubuntu 24.04)

• Step 1 done: host/check-pi-platform.sh passes.
• Step 2 done: flashed, booted, upgraded; ROS installed; ros2 topic list works.
• Step 5 (display) done. ST7789 works on lgpio through Blinka (rpi-lgpio, no RPi.GPIO). Two gotchas: pass cs=None (the kernel drives CE0; claiming GPIO8 raises "GPIO busy"), and the 240x240 glass sits at y_offset=80 in the controller's RAM, for every rotation (the driver rotates in software and leaves the scan direction fixed). Mounted pose (microSD end up, USB-C edge on the left) needs content turned 90 degrees clockwise: rotation=270. Full-frame push is ~23 fps through the driver; the face pushes raw RGB565 with _block and reaches ~27-28 fps.
• Not done: audio (wm8960-soundcard overlay + mixer), camera (cam -l, camera_ros), PWM (waits for servos). Ask before rebooting the Pi.

Package 0b (USB link): Pi side and talos side working

• Pi: dtoverlay=dwc2,dr_mode=peripheral; robot-usb-gadget.service builds a configfs gadget (NCM usb0 + ACM ttyGS0, host MAC 02:68:65:72:6d:01, robot MAC 02:68:65:72:6d:02) before networking; serial-getty@ttyGS0 is enabled; /etc/netplan/60-usb0.yaml gives usb0 10.55.0.2/30 with no gateway, so the default route stays on Wi-Fi. Installed by pi/install-usb-gadget.sh (a backup of config.txt is config.txt.bak-usbgadget). NCM works on the Pi 4 with kernel 1065; ECM was not needed.
• netplan gotcha: match the gadget interface by name: usb0. A macaddress: match becomes PermanentMACAddress= in networkd, which a gadget interface lacks, so it stays unmanaged.
• talos (Omarchy, NetworkManager): host/omarchy/robot-usb-link.sh (needs sudo) adds profile hermes-robot-usb: 10.55.0.1/30 on the interface with MAC 02:68:65:72:6d:01, priority 100, never-default. Verified from talos: ping ~2.4 ms, SSH over the link.
• Not yet verified: serial login prompt (talos's /dev/ttyACM0 is root:uucp; use sudo screen /dev/ttyACM0 115200). The hermes account has no password, so the console shows a login prompt but cannot log in until the owner sets one; no autologin by design. Also not done: the nftables rewrite, the Pi booting with Wi-Fi off, replug and second-host recovery, get_throttled after a servo sweep on the splitter, the NixOS snippet, and straylight/other-host testing. Currently the Pi is powered from talos's USB port (bench test, no servos).

Face (ros/hermes_face)

• render.py: numpy port of docs/face-prototype.html, flat face only (head and lowpoly not ported). Phosphor and vector styles. States: sleeping idle listening thinking looking speaking. sleeping (new) is the "no agent connected" pose: eyes closed to thin lines, mouth short, dim and slowly breathing. looking returns to the state it interrupted. Tone mapping is a lookup table (RGB and RGB565 tables), glow is computed at half resolution, rotation is a free np.rot90.
• display.py: ST7789 driver plus an async pusher (render overlaps the SPI transfer).
• face_node.py: node hermes_face; subscribes /hermes/state (std_msgs/String) and /joint_states (pan_joint, tilt_joint, radians); starts in initial_state (sleeping), so it runs with nothing else up. Parameters: rotation (270), x_offset (0), y_offset (80), baudrate, fps, output (st7789 or none), phosphor (P7), style, persistence_ms, focus, jitter, intensity, initial_state.
• demo.py: no ROS. python -m hermes_face.demo --sequence cycles the states on the panel; --png-dir DIR writes a PNG per state without hardware.
• Tests: python3 -m pytest test in ros/hermes_face (25 pass on the Pi). Renderer parameters (focus, persistence_ms, intensity, jitter) are clamped; fps is clamped to 1-60.
• Measured on the Pi 4: ~9 ms per frame in isolation. With the CPU at full clock: 24% of a core at 20 fps and 40% at 30 fps (target was under 40% at 20 fps or more). Under ondemand the same load reads 40% at 20 fps and ~67% at 30 fps. No C++ rewrite was needed.
• Not yet: audio levels for the mouth (/audio/levels), hermes_mcp publishing states, launch file in hermes_bringup, head/lowpoly shapes, DotStar LEDs, button mute.
• Open: IPS black level. The backlight is on at full brightness, so black reads dark gray on camera. Dimming it needs a software PWM on GPIO26 (not a hardware PWM pin).

Next

1. Finish package 0b: nftables rewrite (accept 4713/8765 only on usb0 from 10.55.0.1), Wi-Fi-off boot test, replug recovery, NixOS snippet in host/nixos/.
2. Audio (package 1; needs the wm8960-soundcard overlay and a reboot), camera (package 3), then the rest of the packages in HANDOFF.md.

Repository

Branch master. .gitignore covers .remember/, caches, .venv/, *.orig, *.rej and pi/50-cloud-init.yaml. tools/check-pi-platform.sh duplicates host/check-pi-platform.sh and can probably go.

Security review notes (parked until the USB link is up)

An automated review of the initial commit flagged three items. All stem from the code predating the USB-gadget design (HANDOFF.md package 0b); none is exposed until the Pi runs the services.

• pi/robot_mcp_server.py: plain HTTP, ROBOT_MCP_BIND defaults to 0.0.0.0. Plan: default to 10.55.0.2, start after usb0.
• pi/pipewire/50-network-server.conf: TCP 4713 on all interfaces, unrestricted. Plan: keep, comment that the firewall is the protection.
• pi/nftables-robot.nft: still the Pi Zero version (single host IP, any interface). Package 0b rewrites it to accept only on the USB interface from 10.55.0.1.
• pi/install.sh permissions looked fine (/etc/robot-mcp.env is root:$USER, 640).

The owner wants to confirm the real IPs on the link before changing any of this. If the USB link doesn't work, revisit: TLS or a Tailscale-only bind for MCP and audio.