Microscope camera kiosk

Touchscreen kiosk for the Raspberry Pi HQ camera (IMX477) used as a
microscope: live preview from boot, raw frame recording, full-resolution
stills, and automatic capture-SSD mounting.

- app.py: GTK3 fullscreen UI over cage — preview, REC/STOP, PHOTO,
  90-degree rotate button, tap-to-open exposure/gain/settings sliders,
  and an "SSD NOT MOUNTED" badge
- camera.py: picamera2 wrapper with separate video (ISP preview + packed
  12-bit raw) and still (4056x3040) configurations
- recorder.py: writer thread turning the raw stream into one Bayer frame
  per file plus index.jsonl/session.json, with dropped/missed accounting
- photos.py: still capture to DNG + JPEG, and a background worker that
  renders a viewable 16-bit sRGB TIFF from the 12-bit Bayer frame
- storage.py: SSD mount state and the date/time/format session layout
- tools/unpack_raw.py: desktop-side unpacker/demosaicer
- system/ + install.sh: systemd units, udev rule, mount helper, sudoers

Note: raw frames are written byte-for-byte as the sensor produced them, so
they stay decodeable regardless of how the stills pipeline evolves.

system/microscope-ssd

@@ -0,0 +1,96 @@
+#!/bin/bash
+# Manage the microscope capture SSD mount.
+#
+#   microscope-ssd mount    mount the SSD (waits briefly for it to appear)
+#   microscope-ssd umount   flush and unmount safely
+#   microscope-ssd status   print: mounted | stale | unmounted | absent
+#
+# Called by the udev-triggered microscope-ssd-mount.service when the drive is
+# plugged in, by fstab at boot, and by the kiosk UI (through a NOPASSWD sudoers
+# entry) when the operator taps MOUNT SSD.
+#
+# stdout stays machine-readable (status) while everything also lands in a log
+# file, because udev and systemd capture stdout in ways that are awkward to read.
+set -u
+
+MOUNT_POINT="${MICROSCOPE_MOUNT:-/mnt/microscope}"
+UUID="${MICROSCOPE_UUID:-caf4320b-0fa3-4674-bfa9-f17f6165f681}"
+OWNER="${MICROSCOPE_OWNER:-tyler:tyler}"
+DEV="/dev/disk/by-uuid/${UUID}"
+LOG_FILE="${MICROSCOPE_LOG:-/run/microscope-ssd.log}"
+
+log() {
+    local message="microscope-ssd: $*"
+    echo "$message" >>"$LOG_FILE" 2>/dev/null || true
+    echo "$message"
+}
+
+in_mounts() { grep -qs " ${MOUNT_POINT} " /proc/self/mounts; }
+
+do_status() {
+    # 'stale' means a mount entry survived a yank: the device node is gone.
+    if in_mounts; then
+        if [ -e "$DEV" ]; then echo mounted; else echo stale; fi
+    elif [ -e "$DEV" ]; then
+        echo unmounted
+    else
+        echo absent
+    fi
+}
+
+do_mount() {
+    mkdir -p "$MOUNT_POINT"
+
+    if in_mounts; then
+        if [ -e "$DEV" ]; then
+            log "already mounted"
+            return 0
+        fi
+        log "clearing stale mount entry"
+        umount -l "$MOUNT_POINT" 2>/dev/null || true
+    fi
+
+    for _ in $(seq 1 40); do
+        [ -e "$DEV" ] && break
+        sleep 0.25
+    done
+    if [ ! -e "$DEV" ]; then
+        log "SSD not present ($DEV)"
+        return 1
+    fi
+
+    if mount -t ext4 -o noatime,errors=remount-ro "$DEV" "$MOUNT_POINT"; then
+        chown "$OWNER" "$MOUNT_POINT" 2>/dev/null || true
+        chmod 755 "$MOUNT_POINT" 2>/dev/null || true
+        log "mounted $DEV at $MOUNT_POINT"
+        return 0
+    fi
+    log "mount failed"
+    return 1
+}
+
+do_umount() {
+    if ! in_mounts; then
+        log "not mounted"
+        return 0
+    fi
+    sync
+    if umount "$MOUNT_POINT"; then
+        log "unmounted (safe to unplug)"
+        return 0
+    fi
+    log "unmount failed - something is still using $MOUNT_POINT"
+    return 1
+}
+
+ACTION="${1:-status}"
+case "$ACTION" in
+    mount|umount) log "--- $(date -Is) action=$ACTION euid=$(id -u) ---" ;;
+esac
+
+case "$ACTION" in
+    mount)  do_mount ;;
+    umount) do_umount ;;
+    status) do_status ;;
+    *)      echo "usage: $0 {mount|umount|status}" >&2; exit 2 ;;
+esac