diff --git a/src/stm32/n32g45x_adc.c b/src/stm32/n32g45x_adc.c
index d27e70c9..52cee2f5 100644
--- a/src/stm32/n32g45x_adc.c
+++ b/src/stm32/n32g45x_adc.c
@@ -14,6 +14,8 @@
 #include "sched.h" // sched_shutdown
 #include "n32g45x_adc.h" // ADC
 
+#define ADC_INVALID_PIN 0xFF
+
 DECL_CONSTANT("ADC_MAX", 4095);
 
 #define ADC_TEMPERATURE_PIN 0xfe
@@ -21,42 +23,42 @@ DECL_ENUMERATION("pin", "ADC_TEMPERATURE", ADC_TEMPERATURE_PIN);
 
 static const uint8_t adc_pins[] = {
     // ADC1
-    0, GPIO('A', 0), GPIO('A', 1), GPIO('A', 6),
-    GPIO('A', 3), GPIO('F', 4), 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    ADC_TEMPERATURE_PIN, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
+    ADC_INVALID_PIN, GPIO('A', 0), GPIO('A', 1), GPIO('A', 6),
+    GPIO('A', 3), GPIO('F', 4), ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_TEMPERATURE_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
     // ADC2
-    0, GPIO('A', 4), GPIO('A', 5), GPIO('B', 1),
+    ADC_INVALID_PIN, GPIO('A', 4), GPIO('A', 5), GPIO('B', 1),
     GPIO('A', 7), GPIO('C', 4), GPIO('C', 0), GPIO('C', 1),
     GPIO('C', 2), GPIO('C', 3), GPIO('F', 2), GPIO('A', 2),
-    GPIO('C', 5), GPIO('B', 2), 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
+    GPIO('C', 5), GPIO('B', 2), ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
 #if CONFIG_MACH_N32G455 // ADC3/4 for G455 only
     // ADC3
-    0, GPIO('B', 11), GPIO('E', 9), GPIO('E', 13),
+    ADC_INVALID_PIN, GPIO('B', 11), GPIO('E', 9), GPIO('E', 13),
     GPIO('E', 12), GPIO('B', 13), GPIO('E', 8), GPIO('D', 10),
     GPIO('D', 11), GPIO('D', 12), GPIO('D', 13), GPIO('D', 14),
     GPIO('B', 0), GPIO('E', 7), GPIO('E', 10), GPIO('E', 11),
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
     // ADC4
-    0, GPIO('E', 14), GPIO('E', 15), GPIO('B', 12),
-    GPIO('B', 14), GPIO('B', 15), 0, 0,
-    0, 0, 0, 0,
-    GPIO('D', 8), GPIO('D', 9), 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
-    0, 0, 0, 0,
+    ADC_INVALID_PIN, GPIO('E', 14), GPIO('E', 15), GPIO('B', 12),
+    GPIO('B', 14), GPIO('B', 15), ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    GPIO('D', 8), GPIO('D', 9), ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
+    ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN, ADC_INVALID_PIN,
 #endif
 };