diff --git a/sonoff/_changelog.ino b/sonoff/_changelog.ino
index d82502b4d..249c87014 100644
--- a/sonoff/_changelog.ino
+++ b/sonoff/_changelog.ino
@@ -1,6 +1,7 @@
 /*********************************************************************************************\
  * 6.6.0.17 20191009
  * Add command SetOption34 0..255 to set backlog delay. Default value is 200 (mSeconds) (#6562)
+ * Add command Gpio 255 to show physical GPIO configuration of all non-flash pins (#6407)
  *
  * 6.6.0.16 20191008
  * Change PZEM004T default address mask from 0.0.0.x to 192.168.1.x for legacy reason (#6585)
diff --git a/sonoff/language/bg-BG.h b/sonoff/language/bg-BG.h
index 482c6284a..609da691e 100644
--- a/sonoff/language/bg-BG.h
+++ b/sonoff/language/bg-BG.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Подсветка"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/cs-CZ.h b/sonoff/language/cs-CZ.h
index 2df00a647..c0e3fefdf 100644
--- a/sonoff/language/cs-CZ.h
+++ b/sonoff/language/cs-CZ.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/de-DE.h b/sonoff/language/de-DE.h
index 5849a1a46..f92507180 100644
--- a/sonoff/language/de-DE.h
+++ b/sonoff/language/de-DE.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/el-GR.h b/sonoff/language/el-GR.h
index 7ccf5ae40..e07d8811b 100644
--- a/sonoff/language/el-GR.h
+++ b/sonoff/language/el-GR.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/en-GB.h b/sonoff/language/en-GB.h
index 28008be9e..a18f2342e 100644
--- a/sonoff/language/en-GB.h
+++ b/sonoff/language/en-GB.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/es-ES.h b/sonoff/language/es-ES.h
index b2fc99e75..193cc57e7 100644
--- a/sonoff/language/es-ES.h
+++ b/sonoff/language/es-ES.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/fr-FR.h b/sonoff/language/fr-FR.h
index 101b659c7..aefca66f4 100644
--- a/sonoff/language/fr-FR.h
+++ b/sonoff/language/fr-FR.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "RétroÉcl"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/he-HE.h b/sonoff/language/he-HE.h
index 96fbc8863..5830b394f 100644
--- a/sonoff/language/he-HE.h
+++ b/sonoff/language/he-HE.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/hu-HU.h b/sonoff/language/hu-HU.h
index ae19f1d75..dd4d5a645 100644
--- a/sonoff/language/hu-HU.h
+++ b/sonoff/language/hu-HU.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Háttérfény"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/it-IT.h b/sonoff/language/it-IT.h
index 51aa07540..4ec8728f2 100644
--- a/sonoff/language/it-IT.h
+++ b/sonoff/language/it-IT.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/ko-KO.h b/sonoff/language/ko-KO.h
index 2c11f02db..d1729fbce 100644
--- a/sonoff/language/ko-KO.h
+++ b/sonoff/language/ko-KO.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/nl-NL.h b/sonoff/language/nl-NL.h
index 19f7872b8..7be14d2b5 100644
--- a/sonoff/language/nl-NL.h
+++ b/sonoff/language/nl-NL.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/pl-PL.h b/sonoff/language/pl-PL.h
index 9fceb490d..6d5767ed7 100644
--- a/sonoff/language/pl-PL.h
+++ b/sonoff/language/pl-PL.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/pt-BR.h b/sonoff/language/pt-BR.h
index ccea3e78d..1b2aa0ef9 100644
--- a/sonoff/language/pt-BR.h
+++ b/sonoff/language/pt-BR.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Luz de fundo"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/pt-PT.h b/sonoff/language/pt-PT.h
index e89e01710..54cc61d87 100644
--- a/sonoff/language/pt-PT.h
+++ b/sonoff/language/pt-PT.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Luz negra"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/ru-RU.h b/sonoff/language/ru-RU.h
index 441994c1b..fbf006e3d 100644
--- a/sonoff/language/ru-RU.h
+++ b/sonoff/language/ru-RU.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/sk-SK.h b/sonoff/language/sk-SK.h
index 757e48173..d26e418d0 100644
--- a/sonoff/language/sk-SK.h
+++ b/sonoff/language/sk-SK.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/sv-SE.h b/sonoff/language/sv-SE.h
index 200023970..72b977208 100644
--- a/sonoff/language/sv-SE.h
+++ b/sonoff/language/sv-SE.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/tr-TR.h b/sonoff/language/tr-TR.h
index c8d006513..4fae8e0cf 100755
--- a/sonoff/language/tr-TR.h
+++ b/sonoff/language/tr-TR.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/uk-UK.h b/sonoff/language/uk-UK.h
index daaf299fa..2b046389d 100644
--- a/sonoff/language/uk-UK.h
+++ b/sonoff/language/uk-UK.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/zh-CN.h b/sonoff/language/zh-CN.h
index 1fcb3ef3d..8ca50943c 100644
--- a/sonoff/language/zh-CN.h
+++ b/sonoff/language/zh-CN.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/language/zh-TW.h b/sonoff/language/zh-TW.h
index 6939de541..bc535f70e 100644
--- a/sonoff/language/zh-TW.h
+++ b/sonoff/language/zh-TW.h
@@ -541,6 +541,9 @@
 #define D_SENSOR_SAIR_TX       "SAir Tx"
 #define D_SENSOR_SPI_CS        "SPI CS"
 #define D_SENSOR_SPI_DC        "SPI DC"
+#define D_SENSOR_SPI_MISO      "SPI MISO"
+#define D_SENSOR_SPI_MOSI      "SPI MOSI"
+#define D_SENSOR_SPI_CLK       "SPI CLK"
 #define D_SENSOR_BACKLIGHT     "Backlight"
 #define D_SENSOR_PMS5003       "PMS5003"
 #define D_SENSOR_SDS0X1_RX     "SDS0X1 Rx"
diff --git a/sonoff/sonoff_template.h b/sonoff/sonoff_template.h
index ca09fce44..0bb460800 100644
--- a/sonoff/sonoff_template.h
+++ b/sonoff/sonoff_template.h
@@ -285,6 +285,10 @@ const char kSensorNames[] PROGMEM =
   D_SENSOR_SM2135_CLK "|" D_SENSOR_SM2135_DAT "|"
   ;
 
+const char kSensorNamesFixed[] PROGMEM =
+  D_SENSOR_SPI_MISO "|" D_SENSOR_SPI_MOSI "|" D_SENSOR_SPI_CLK "|"
+  D_SENSOR_USER;
+
 // User selectable ADC0 functionality
 enum UserSelectableAdc0 {
   ADC0_NONE,           // Not used
diff --git a/sonoff/support.ino b/sonoff/support.ino
index 8dbbc3316..33841cc26 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -1067,11 +1067,16 @@ void SetModuleType()
   my_module_type = (USER_MODULE == Settings.module) ? Settings.user_template_base : Settings.module;
 }
 
+bool FlashPin(uint32_t pin)
+{
+  return (((pin > 5) && (pin < 9)) || (11 == pin));
+}
+
 uint8_t ValidPin(uint32_t pin, uint32_t gpio)
 {
   uint8_t result = gpio;
 
-  if (((pin > 5) && (pin < 9)) || (11 == pin)) {
+  if (FlashPin(pin)) {
     result = GPIO_NONE;  // Disable flash pins GPIO6, GPIO7, GPIO8 and GPIO11
   }
   if ((WEMOS == Settings.module) && (!Settings.flag3.user_esp8285_enable)) {
diff --git a/sonoff/support_command.ino b/sonoff/support_command.ino
index b36abf714..459048088 100644
--- a/sonoff/support_command.ino
+++ b/sonoff/support_command.ino
@@ -868,11 +868,25 @@ void CmndGpio(void)
     Response_P(PSTR("{"));
     bool jsflg = false;
     for (uint32_t i = 0; i < sizeof(Settings.my_gp); i++) {
-      if (ValidGPIO(i, cmodule.io[i])) {
+      if (ValidGPIO(i, cmodule.io[i]) || ((GPIO_USER == XdrvMailbox.payload) && !FlashPin(i))) {
         if (jsflg) { ResponseAppend_P(PSTR(",")); }
         jsflg = true;
+        uint8_t sensor_type = Settings.my_gp.io[i];
+        if (!ValidGPIO(i, cmodule.io[i])) {
+          sensor_type = cmodule.io[i];
+          if (GPIO_USER == sensor_type) {  // A user GPIO equals a not connected (=GPIO_NONE) GPIO here
+            sensor_type = GPIO_NONE;
+          }
+        }
+        uint8_t sensor_name_idx = sensor_type;
+        const char *sensor_names = kSensorNames;
+        if (sensor_type > GPIO_FIX_START) {
+          sensor_name_idx = sensor_type - GPIO_FIX_START -1;
+          sensor_names = kSensorNamesFixed;
+        }
         char stemp1[TOPSZ];
-        ResponseAppend_P(PSTR("\"" D_CMND_GPIO "%d\":{\"%d\":\"%s\"}"), i, Settings.my_gp.io[i], GetTextIndexed(stemp1, sizeof(stemp1), Settings.my_gp.io[i], kSensorNames));
+        ResponseAppend_P(PSTR("\"" D_CMND_GPIO "%d\":{\"%d\":\"%s\"}"),
+          i, sensor_type, GetTextIndexed(stemp1, sizeof(stemp1), sensor_name_idx, sensor_names));
       }
     }
     if (jsflg) {