diff --git a/src/gpio.c b/src/gpio.c
--- a/src/gpio.c
+++ b/src/gpio.c
@@ -6,6 +6,48 @@
 
 #include "gpio.h"
 
+#define CHANGE_PERIOD_MS 100
+#define CHANGE_ELAPSED (HAL_GetTick() - change_time_reset) > CHANGE_PERIOD_MS
+#define CHANGE_RESET change_time_reset = HAL_GetTick()
+
+// Increase on each press, and increase at a fast rate after duration elapsed of continuously holding down... somehow...
+static uint32_t change_time_reset = 0;
+
+
+// Increment/decrement unsigned variable with up/down buttons
+void user_input(uint16_t* to_modify)
+{
+    if(CHANGE_ELAPSED) {
+        if(!HAL_GPIO_ReadPin(SW_UP) ) {
+            CHANGE_RESET;
+            (*to_modify)++;
+        }
+        else if(!HAL_GPIO_ReadPin(SW_DOWN) && (*to_modify) > 0) {
+            CHANGE_RESET;
+            (*to_modify)--;
+        }
+    }
+}
+
+
+// Increment/decrement signed variable with up/down buttons
+void user_input_signed(int32_t* to_modify)
+{
+	//fixme: need to cast to 16/32 bits correctly
+    if(CHANGE_ELAPSED) {
+        if(!HAL_GPIO_ReadPin(SW_UP) ) {
+            CHANGE_RESET;
+            if (*to_modify < 32768)
+            	(*to_modify)++;
+        }
+        else if(!HAL_GPIO_ReadPin(SW_DOWN)) {
+            CHANGE_RESET;
+            if (*to_modify >= -32768)
+            	(*to_modify)--;
+        }
+    }
+}
+
 
 // Initialize GPIOs
 void gpio_init(void)