fix(x4): assert the battery-MOSFET latch at boot

One X4 hardware revision does not self-latch its battery rail, so it seems
unresponsive off USB power. selectDevice(XteinkX4) runs holdPowerRails(),
which asserts GPIO13; that is a no-op on units that self-latch through a
pull. Matches the fix CrossInk shipped in 1.5.0-rc-2.

Deliberately no panel-controller probe on either device. Probing the X4
display bus hung display init (bit-banged GPIO on pins the mounted SD card
shares), and calling selectDevice(XteinkX3) before Storage.begin() switched
sd.powerEnable to GPIO13 and hung SD mount on X3. X3 keeps ACTIVE on the
XTEINK_X4 default until setDisplayX3(), as in every prior release, so its
boot path is unchanged from 4.7.1.

Adds XteinkDetect to lib_deps, a CRUMBLE_DISABLE_PANEL_PROBE escape hatch
and a tiny-bitter-noprobe diagnostic env.

Author: imshentastic

lib/hal/HalDisplay.cpp

@@ -1,7 +1,9 @@
 #include <HalDisplay.h>
 #include <HalGPIO.h>
+#include <XteinkDetect.h>
 
 #include "HalSpiBus.h"
+#include "Logging.h"
 
 // Global HalDisplay instance
 HalDisplay display;
@@ -20,6 +22,8 @@ void HalDisplay::begin(bool seamless) {
     einkDisplay.setDisplayX3();
   }
 
+  // No panel-controller probe here: bit-banging the display bus at this point
+  // hung X4 boot (SD shares SCLK/MOSI and is already mounted). See setup().
   einkDisplay.begin();
 
   if (seamless) {

platformio.ini

@@ -49,7 +49,10 @@ crossink_version = 1.3.0
 ;         the stock 6.25 MB slot again (SD-card flash from CrossInk works).
 ; v4.7.1: Portuguese hyphenation (+ 'pol' ISO mapping), status-bar deghost
 ;         zone sized from layout math, prebake tool-build repair.
-crumble_version = 4.7.1
+; v4.7.2: freeink-sdk resynced to upstream e6a8048; X4 battery-latch assert
+;         for the non-self-latching revision; settings deferred-save log
+;         spam fixed. Newer UC8279/UC8179 panels remain unsupported.
+crumble_version = 4.7.2
 
 [base]
 platform = https://github.com/pioarduino/platform-espressif32/releases/download/55.03.37/platform-espressif32.zip
@@ -280,6 +283,14 @@ lib_deps =
   SDCardManager=symlink://freeink-sdk/libs/hardware/SDCardManager
   BoardConfig=symlink://freeink-sdk/libs/hardware/BoardConfig
   PowerManager=symlink://freeink-sdk/libs/hardware/PowerManager
+; CrumBLE 4.7.2: XteinkDetect supplies applyXteinkDisplayController(), the
+; bus probe that tells an original X4/X3 (SSD1677 / UC8253) from the newer
+; production runs that swapped in an UltraChip UC8179 / UC8279. Without it
+; BoardConfig::ACTIVE.displayController never leaves its profile default and
+; a new-panel unit picks the wrong driver -> dead display. We keep using our
+; own gpio.deviceIsX3() for the X3-vs-X4 split; only the controller probe is
+; taken from here.
+  XteinkDetect=symlink://freeink-sdk/libs/hardware/XteinkDetect
   bblanchon/ArduinoJson @ 7.4.2
   ricmoo/QRCode @ 0.0.1
   bitbank2/PNGdec @ ^1.0.0
@@ -541,3 +552,13 @@ extends = simulator_base
 build_flags =
   ${simulator_base.build_flags}
   -DSIMULATOR_DEVICE_X3
+
+; Diagnostic variant of tiny-bitter: identical firmware with the boot-time
+; panel-controller probe compiled out, plus DBG logging. Used to bisect whether
+; a boot problem comes from the probe or from the freeink-sdk update itself.
+; Not a shipping env.
+[env:tiny-bitter-noprobe]
+extends = env:tiny-bitter
+build_flags =
+  ${env:tiny-bitter.build_flags}
+  -DCRUMBLE_DISABLE_PANEL_PROBE

src/main.cpp

@@ -1,5 +1,7 @@
 #include <Arduino.h>
 #include <BluetoothHIDManager.h>
+#include <BoardConfig.h>   // CrumBLE 4.7.2: panel-controller profile selection
+#include <XteinkDetect.h>  // CrumBLE 4.7.2: pre-SD panel-controller probe
 
 // v18.9.9.245: for BT-off-by-default boot-time memory release. Same header
 // used by CrossPointWebServerActivity's FT-enter release path.
@@ -2830,6 +2832,43 @@ void setup() {
           gpio.deviceIsX3() ? "X3" : "X4", gpio.isUsbConnected() ? 1 : 0, isSilentReboot ? 1 : 0,
           static_cast<unsigned long>(snapshotTarget));
 
+  // CrumBLE 4.7.2: resolve which panel controller this unit carries, BEFORE the
+  // SD card is mounted. Xteink switched newer X4/X3 runs from SSD1677/UC8253 to
+  // the UltraChip UC8179/UC8279 on the same board, so the driver can only be
+  // picked by asking the silicon -- but the probe bit-bangs the display pins as
+  // raw GPIO, and SD shares SCLK/MOSI on this hardware. Running it after
+  // Storage.begin() hung X4 boot (the disturbed card clamps the shared bus and
+  // the panel never hears CMD_SOFT_RESET); XteinkDetect.h's contract is to call
+  // it before SDCardManager::begin(), which is what this placement honors.
+  //
+  // The probe reads its pins from BoardConfig::ACTIVE, so the X3/X4 profile has
+  // to be chosen first. ACTIVE defaults to XTEINK_X4; point it at the X3 sibling
+  // when our own fingerprint says X3, so the promotion lands on UC8253->UC8279
+  // rather than SSD1677->UC8179. On a confirmed X3 promotion, switch to the
+  // XteinkX3Uc8279 profile: HalDisplay::begin()'s setDisplayX3() re-selects
+  // XteinkX3 otherwise, which would reset displayController back to UC8253.
+  //
+  // Fail-safe: promotion needs two independent passes to both match the UC81xx
+  // VER/FLG signature AND agree byte-for-byte. An original SSD1677/UC8253 does
+  // not answer register 0x70 at all, so the bus floats, both passes fail, and
+  // the profile default stands -- existing units keep today's driver.
+#ifndef CRUMBLE_DISABLE_PANEL_PROBE
+  // v4.7.2: assert the X4 battery-MOSFET latch (GPIO13) via holdPowerRails().
+  // No-op on self-latching X4s; the revision that doesn't self-latch stays
+  // powered only while the button is held without it.
+  //
+  // X4 only, and nothing here on X3 -- both learned on hardware. Probing the X4
+  // display bus hung display init; calling selectDevice(XteinkX3) here switched
+  // sd.powerEnable to GPIO13 and hung Storage.begin(). X3 must keep ACTIVE on the
+  // XTEINK_X4 default until setDisplayX3(), as every release before this one.
+  if (!gpio.deviceIsX3()) {
+    BoardConfig::selectDevice(BoardConfig::Board::XteinkX4);
+    LOG_INF("DISPLAY", "X4: SSD1677 (default); battery latch asserted");
+  } else {
+    LOG_INF("DISPLAY", "X3: UC8253 (default); profile deferred to setDisplayX3()");
+  }
+#endif
+
   // SD Card Initialization
   // We need 6 open files concurrently when parsing a new chapter
   if (!Storage.begin()) {