diff --git a/stm-firmware/include/stm-periph/stm32-gpio-macros.h b/stm-firmware/include/stm-periph/stm32-gpio-macros.h
index f94e4da..0dd3097 100644
--- a/stm-firmware/include/stm-periph/stm32-gpio-macros.h
+++ b/stm-firmware/include/stm-periph/stm32-gpio-macros.h
@@ -25,6 +25,7 @@
 #define PUPDR_DELETE(pin) ~(0x3U << ((pin) * 2))
 #define OUTPUT(pin)  (0x01U << ((pin) * 2))
 #define PULLUP(pin) (0x1U << ((pin)* 2))
+#define PULLDOWN(pin) (0x2U << ((pin)* 2))
 #define ALTFUNC(pin) ((0x2) << ((pin) * 2))
 #define PINMASK(pin) ((0x3) << ((pin) * 2))
 #define SETAF(PORT,PIN,AF)  PORT->AFR[((PIN) < 8 ? 0 : 1)] |= (AF) << (((PIN) < 8 ? (PIN) : ((PIN) - 8)) * 4)