Kai Mallari's Notes'

EC - Sleep Wake Recovery

3 min read

Sleep/Wake Recovery

Symptom: Laptop screen went dark (lid closed, power interrupted, or idle timeout). On wake: tethering not working, external display blank, iPad disconnected. Root Cause: macOS sleep powers down the USB bus, drops the PTP session, deregisters Bonjour services, and may lose the HDMI handshake. Referred from: DIT Triage - C1 Crashed, DIT Triage - Display Problems, DIT Triage - Tether Drops

Diagnosis

The Cascade (what broke)

When macOS sleeps, these things happen simultaneously:

  1. USB bus powers down → camera PTP session terminates → tethering stops
  2. HDMI output drops → external display loses signal → may not auto-recover on wake
  3. Bonjour service deregisters → Capture Pilot and Live for Studio disconnect from iPads
  4. Wi-Fi may disconnect or switch to low-power mode → network path to router interrupted
  5. If sleep lasted long enough for DHCP lease to expire → IP addresses may change

This is not a single failure — it is a cascade of five independent subsystem failures that all need individual recovery.

Fix

Recovery Sequence (in this order — order matters)

Step 1: Wake the laptop

  • Open lid or press a key. If FileVault is enabled, enter the login password. If this is the photographer’s laptop and you don’t have the password, you’re locked out. Call the photographer.
  • Budget: 5-15 seconds.

Step 2: Recover the display

  • Wait 10-20 seconds for the HDMI handshake to re-establish. The external display may flash or cycle inputs.
  • If the display doesn’t come back: unplug the HDMI cable from the adapter, wait 5 seconds, replug.
  • If that doesn’t work: unplug the USB-C adapter from the laptop, wait 5 seconds, replug.
  • If still no display: the adapter may have overheated during sleep. Let it cool for a minute, or use a different adapter.
  • Budget: 10-30 seconds.

Step 3: Recover USB/tethering

  • Check if Capture One shows “Camera Detected.” It may auto-reconnect.
  • If not: disconnect the USB tether cable from the laptop, wait 5 seconds, reconnect.
  • If still not detected: power cycle the camera (off, wait 10 seconds, on).
  • Budget: 10-20 seconds.

Step 4: Verify Capture One

  • If Capture One is open and the session is loaded, skip this step.
  • If Capture One was closed by macOS during sleep (rare but possible on low memory): relaunch and open the session.
  • Budget: 5-15 seconds.

Step 5: Recover network services

  • Check Wi-Fi connection on the laptop. If disconnected, reconnect to the DIT router network.
  • Capture Pilot: check the iPad. It should reconnect automatically within 15 seconds. If not, force-close and reopen the app.
  • Live for Studio: check the iPad. If “Session Not Found,” the Bonjour service may need to re-register. In Capture One, stop and restart the Live for Studio share.
  • Budget: 15-30 seconds.

Step 6: Test end-to-end

  • Trigger one capture. Verify it appears in Capture One, on the external display, and on the iPad.

Total recovery: 45-120 seconds depending on how many components need manual recovery.

Prevention

  • Disable sleep entirely: System Settings > Battery > Low Power Mode OFF. Options > Prevent automatic sleeping when the display is off ON. Or run caffeinate -d in Terminal (prevents display sleep).
  • Disable lid-close sleep: If using clamshell mode, the laptop must be connected to external power AND an external display. Otherwise, closing the lid triggers sleep. Consider keeping the lid open.
  • Set display timeout to Never: System Settings > Lock Screen > Turn display off after: Never (while on power adapter).
  • Include sleep prevention in pre-shoot checklist: Verify these settings are applied before the first capture, not after the first sleep incident.

Documentation

Graph View

Backlinks