diff --git a/src/stm32/adc.c b/src/stm32/adc.c
index 9f1a6d53..0d3f33ce 100644
--- a/src/stm32/adc.c
+++ b/src/stm32/adc.c
@@ -1,6 +1,6 @@
 // ADC functions on STM32
 //
-// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2019-2020  Kevin O'Connor <kevin@koconnor.net>
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
@@ -15,11 +15,23 @@
 
 DECL_CONSTANT("ADC_MAX", 4095);
 
+#define ADC_TEMPERATURE_PIN 0xfe
+DECL_ENUMERATION("pin", "ADC_TEMPERATURE", ADC_TEMPERATURE_PIN);
+
 static const uint8_t adc_pins[] = {
     GPIO('A', 0), GPIO('A', 1), GPIO('A', 2), GPIO('A', 3),
     GPIO('A', 4), GPIO('A', 5), GPIO('A', 6), GPIO('A', 7),
     GPIO('B', 0), GPIO('B', 1), GPIO('C', 0), GPIO('C', 1),
     GPIO('C', 2), GPIO('C', 3), GPIO('C', 4), GPIO('C', 5),
+
+#if CONFIG_MACH_STM32F1
+    ADC_TEMPERATURE_PIN,
+#elif CONFIG_MACH_STM32F2 || CONFIG_MACH_STM32F407
+    ADC_TEMPERATURE_PIN, 0x00, 0x00,
+#elif CONFIG_MACH_STM32F446
+    0x00, 0x00, ADC_TEMPERATURE_PIN,
+#endif
+
 #if CONFIG_MACH_STM32F4
     0x00, 0x00, 0x00, 0x00,
     GPIO('F', 6), GPIO('F', 7), GPIO('F', 8), GPIO('F', 9),
@@ -29,7 +41,8 @@ static const uint8_t adc_pins[] = {
 };
 
 #if CONFIG_MACH_STM32F1
-#define CR2_FLAGS (ADC_CR2_ADON | (7 << ADC_CR2_EXTSEL_Pos) | ADC_CR2_EXTTRIG)
+#define CR2_FLAGS (ADC_CR2_ADON | (7 << ADC_CR2_EXTSEL_Pos) | ADC_CR2_EXTTRIG \
+                   | ADC_CR2_TSVREFE)
 #else
 #define CR2_FLAGS ADC_CR2_ADON
 #endif
@@ -71,11 +84,11 @@ gpio_adc_setup(uint32_t pin)
     ADC_TypeDef *adc = ADC1;
     uint32_t adc_base = ADC1_BASE;
 #if CONFIG_MACH_STM32F4
-    if (chan >= 16) {
+    if (chan >= 19) {
         // On the STM32F4, some ADC channels are only available from ADC3
         adc = ADC3;
         adc_base += 0x800;
-        chan -= 16;
+        chan -= 19;
     }
 #endif
 
@@ -94,7 +107,13 @@ gpio_adc_setup(uint32_t pin)
         adc->CR2 = CR2_FLAGS;
     }
 
-    gpio_peripheral(pin, GPIO_ANALOG, 0);
+    if (pin == ADC_TEMPERATURE_PIN) {
+#if !CONFIG_MACH_STM32F1
+        ADC123_COMMON->CCR = ADC_CCR_TSVREFE;
+#endif
+    } else {
+        gpio_peripheral(pin, GPIO_ANALOG, 0);
+    }
 
     return (struct gpio_adc){ .adc = adc, .chan = chan };
 }