diff --git a/main/meteo_task.c b/main/meteo_task.c
index 0415774..41e052b 100644
--- a/main/meteo_task.c
+++ b/main/meteo_task.c
@@ -5,11 +5,81 @@
 #include <stdio.h>
 #include <FreeRTOS.h>
 #include <task.h>
+#include <math.h>
+#include <driver/hw_timer.h>
 #include "meteo_task.h"
 #include "ds18b20.h"
 #include "dht.h"
 #include "driver/gpio.h"
 
+static volatile uint32_t timestamp_ms = 0;
+static volatile uint32_t last_revolution_ts = 0;
+
+#define RPM_BUFFER_LEN 10
+static volatile uint16_t rpm_buffer[RPM_BUFFER_LEN] = {};
+static volatile int rpm_buffer_next = 0;
+static volatile int num_valid_average = 0;
+
+static void gpio_isr_handler(void *arg)
+{
+    uint32_t ts = timestamp_ms;
+    uint32_t cycle_ms = ts - last_revolution_ts;
+    last_revolution_ts = ts;
+
+    if (cycle_ms > 0xFFFF) {
+        cycle_ms = 0xFFFF;
+    }
+    rpm_buffer[rpm_buffer_next++] = (uint16_t) cycle_ms;
+    if (rpm_buffer_next == RPM_BUFFER_LEN) {
+        rpm_buffer_next = 0;
+    }
+    if (num_valid_average < RPM_BUFFER_LEN) {
+        num_valid_average++;
+    }
+}
+
+float get_rpm() {
+    float res;
+    float current = (float)(timestamp_ms - last_revolution_ts);
+
+    if (num_valid_average > 0) {
+        // we write num_valid_average only from here, so its safe to assume it stays nonzero
+        float average = 0;
+        int pos = rpm_buffer_next;
+        for (int i = 0; i < num_valid_average; i++) {
+            average += (float) rpm_buffer[pos];
+            pos--;
+            if (pos < 0) {
+                pos = RPM_BUFFER_LEN - 1;
+            }
+        }
+        average /= (float) (num_valid_average);
+
+        // now we have ms per revolution
+
+        if (current > average * 10.0f) {
+            // if wind stopped, invalidate the averaging buffer and use the current time from the last hall event
+            res = current;
+            num_valid_average = 0; // invalidate average results
+        } else {
+            res = average;
+        }
+    } else {
+        res = current;
+    }
+
+    float rpm = 60000.0f / res;
+    if (rpm < 1) {
+        rpm = 0;
+    }
+    return rpm; // RPM
+}
+
+void hw_timer_callback1(void *arg)
+{
+    timestamp_ms++;
+}
+
 void meteo_task(void* pvParameters)
 {
     // Try to unfuck GPIOs
@@ -18,21 +88,32 @@ void meteo_task(void* pvParameters)
     PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTMS_U, FUNC_GPIO14);
     PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTDO_U, FUNC_GPIO15);
 
+    // start timer used for timebase
+    hw_timer_init(hw_timer_callback1, NULL);
+    hw_timer_alarm_us(1000, true); // 1 ms timer
+
+    gpio_config_t io_conf;
+    io_conf.intr_type = GPIO_INTR_POSEDGE;
+    io_conf.mode = GPIO_MODE_INPUT;
+    io_conf.pin_bit_mask = 1 << 14;
+    io_conf.pull_down_en = 1;
+    io_conf.pull_up_en = 0;
+    gpio_config(&io_conf);
+    gpio_install_isr_service(0);
+    gpio_isr_handler_add(14, gpio_isr_handler, NULL);
+
     float dht_hum, dht_temp, ds_temp;
     while (1) {
         // this works ...
         ds_temp = ds18b20_measure_and_read(0, DS18B20_ANY);
-        if (ds_temp != ds_temp) { // NAN
-            printf("Fail to read temp\n");
-        } else {
-            printf("Dallas: %f °C\n", ds_temp);
-        }
 
-        if (dht_read_float_data(DHT_TYPE_DHT11, 12, &dht_hum, &dht_temp)) {
-            printf("DHT: %f °C, %f %%r.H\n", dht_temp, dht_hum);
+        if (!dht_read_float_data(DHT_TYPE_DHT11, 12, &dht_hum, &dht_temp)) {
+            dht_hum = dht_temp = NAN;
         }
 
-        vTaskDelay(pdMS_TO_TICKS(1000));
+        printf("Dallas: %.2f °C, DHT %.2f °C, %.1f %%r.H, HALL %.1f RPM\n", ds_temp, dht_temp, dht_hum, get_rpm());
+
+        vTaskDelay(pdMS_TO_TICKS(500));
     }
 
     vTaskDelete(NULL);