From 9a4f14faf6d8627da07c2cfcb21b55655dcb5dc3 Mon Sep 17 00:00:00 2001 From: mikkeli Date: Fri, 9 Oct 2026 00:49:34 +0900 Subject: [PATCH] USB report: ~3 s per power change; flapping-charger edge case Summarises the measured cost as roughly 3 s blank per PD state change, with keep-awake in the app handling sleep, and notes that a marginal charger renegotiating PD repeatedly would cut the link each time. Co-Authored-By: Claude Opus 5.5 --- docs/impl/reports/USB-TABLET-LINK.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/docs/impl/reports/USB-TABLET-LINK.md b/docs/impl/reports/USB-TABLET-LINK.md index aa9897b..28b8cc8 100644 --- a/docs/impl/reports/USB-TABLET-LINK.md +++ b/docs/impl/reports/USB-TABLET-LINK.md @@ -126,6 +126,9 @@ Three PD unplug/replug cycles while pinging the tablet every 0.5 s: - So with the tablet awake, the hub's PD changes cost **~3.5 s on unplug** (full detach) and **~2.2 s on plug-in** (gadget reconnect only). Everything beyond that came from tablet sleep. - To the Orin, a sleeping tablet is indistinguishable from a dead link, except by heartbeat. +- Rule of thumb: **about 3 s blank per power-state change**. The app keeping the tablet awake (full UI or an overlay widget) takes sleep off the table. +- Known edge case, not a blocker: an underpowered or marginal charger that keeps falling back between PD and 5 V/1 A would cut the link on + every renegotiation, possibly every few seconds. Use a solid PD charger. If the link ever flaps periodically, suspect the charger first. - At ignition, accessory power drops during cranking, so a start is likely to produce both edges back to back (not tested in the car yet).