From 9b7b9e90943e78c0048384407ed98b26331b443b Mon Sep 17 00:00:00 2001
From: Justin Mitchell <justin@jmitch.com>
Date: Mon, 15 Jun 2026 12:26:21 -0400
Subject: [PATCH] Skip X3 fingerprint probe on non-C3 boards

Prevent I2C pin collision on S3/ESP32 boards by skipping the X3/X4 fingerprint probe. The probe's I2C pins (GPIO20/0) conflict with onboard peripherals like the BQ27220 gauge and reconfigure strapping pins. Force deviceType to X4 for non-C3 builds.
---
 lib/hal/HalGPIO.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/hal/HalGPIO.cpp b/lib/hal/HalGPIO.cpp
index 1fffde56..c7cc4622 100644
--- a/lib/hal/HalGPIO.cpp
+++ b/lib/hal/HalGPIO.cpp
@@ -202,12 +202,22 @@ void HalGPIO::begin() {
   SPI.begin(EPD_SCLK, SPI_MISO, EPD_MOSI, EPD_CS);
 #endif
 
+#if FREEINK_MCU_C3
   _deviceType = detectDeviceTypeWithFingerprint();
 
   if (deviceIsX4()) {
     pinMode(BAT_GPIO0, INPUT);
     pinMode(UART0_RXD, INPUT);
   }
+#else
+  // Non-C3 boards (S3/ESP32) are single-device builds; their pins, panel, and
+  // battery backend all come from BoardConfig::ACTIVE. The X3/X4 fingerprint probe
+  // targets Xteink C3 hardware and drives Wire on X3_I2C_SDA/SCL (GPIO20/0) — which
+  // collides with this board's own I2C (e.g. Sticky's BQ27220 gauge shares GPIO0)
+  // and reconfigures strapping pins. Skip it; _deviceType stays X4 ("not X3"),
+  // the correct non-X3 branch for every deviceIsX3() consumer.
+  _deviceType = DeviceType::X4;
+#endif
 }
 
 void HalGPIO::update() {