diff --git a/cpu/esp32/include/periph_cpu.h b/cpu/esp32/include/periph_cpu.h
index 26ac5edb8498b150f65af3162d80708e7b9f34de..8a69809f1831c720276c578f87a68326cd4d635c 100644
--- a/cpu/esp32/include/periph_cpu.h
+++ b/cpu/esp32/include/periph_cpu.h
@@ -206,10 +206,14 @@ typedef enum {
  */
 #define HAVE_ADC_RES_T
 typedef enum {
-    ADC_RES_9BIT = 0,       /**< ADC resolution: 9 bit */
-    ADC_RES_10BIT,          /**< ADC resolution: 10 bit */
-    ADC_RES_11BIT,          /**< ADC resolution: 11 bit */
-    ADC_RES_12BIT,          /**< ADC resolution: 12 bit */
+    ADC_RES_6BIT  = 0xf0,   /**< ADC resolution: 6 bit is not supported */
+    ADC_RES_8BIT  = 0xf1,   /**< ADC resolution: 8 bit is not supported  */
+    ADC_RES_9BIT  = 0,      /**< ADC resolution: 9 bit */
+    ADC_RES_10BIT = 1,      /**< ADC resolution: 10 bit */
+    ADC_RES_11BIT = 2,      /**< ADC resolution: 11 bit */
+    ADC_RES_12BIT = 3,      /**< ADC resolution: 12 bit */
+    ADC_RES_14BIT = 0xf2,   /**< ADC resolution: 14 bit is not supported */
+    ADC_RES_16BIT = 0xf3,   /**< ADC resolution: 16 bit is not supported */
 } adc_res_t;
 /** @} */