diff --git a/optimized_user_settings.cfg b/optimized_user_settings.cfg
index 8d53a42..5496f3f 100644
--- a/optimized_user_settings.cfg
+++ b/optimized_user_settings.cfg
@@ -41,10 +41,17 @@ sensor_mcu: cartographer
 min_temp: 5
 max_temp: 105
 
-# ADXL345 is integrated in Cartographer probe
-# Configure as separate device on Cartographer MCU
+# ============================================================================
+# ADXL345 ACCELEROMETER (integrated in Cartographer probe)
+# ============================================================================
+# IMPORTANT: Select the correct cs_pin for your Cartographer version!
+# - Cartographer V3: cs_pin: cartographer:PA3
+# - Cartographer V4: cs_pin: cartographer:PA0
+# Using the wrong pin causes: "Invalid adxl345 id (got 0 vs e5)"
+# ============================================================================
+
 [adxl345]
-cs_pin: cartographer:PA3
+cs_pin: cartographer:PA3    # ← CHANGE TO cartographer:PA0 FOR V4!
 spi_bus: spi1
 axes_map: x, y, z
 
diff --git a/user_settings_clean.cfg b/user_settings_clean.cfg
index eb197e3..af3c4d9 100644
--- a/user_settings_clean.cfg
+++ b/user_settings_clean.cfg
@@ -41,10 +41,17 @@ sensor_mcu: cartographer
 min_temp: 5
 max_temp: 105
 
-# ADXL345 is integrated in Cartographer probe
-# Configure as separate device on Cartographer MCU
+# ============================================================================
+# ADXL345 ACCELEROMETER (integrated in Cartographer probe)
+# ============================================================================
+# IMPORTANT: Select the correct cs_pin for your Cartographer version!
+# - Cartographer V3: cs_pin: cartographer:PA3
+# - Cartographer V4: cs_pin: cartographer:PA0
+# Using the wrong pin causes: "Invalid adxl345 id (got 0 vs e5)"
+# ============================================================================
+
 [adxl345]
-cs_pin: cartographer:PA3
+cs_pin: cartographer:PA3    # ← CHANGE TO cartographer:PA0 FOR V4!
 spi_bus: spi1
 axes_map: x, y, z