diff --git a/F0-nolib/Socket_fans/hardware.c b/F0-nolib/Socket_fans/hardware.c
index 827dabf..9b5d832 100644
--- a/F0-nolib/Socket_fans/hardware.c
+++ b/F0-nolib/Socket_fans/hardware.c
@@ -23,8 +23,9 @@
 
 #include "adc.h"
 #include "hardware.h"
+#include "proto.h"
 
-uint8_t ledsON = 0;
+buzzer_state buzzer = BUZZER_OFF; // buzzer state
 
 void adc_setup(){
     uint16_t ctr = 0; // 0xfff0 - more than 1.3ms
@@ -187,6 +188,62 @@ void Jump2Boot(){
     SysMemBootJump();
 }
 
+void buzzer_chk(){ // check buzzer state
+    static uint32_t lastTms = 0;
+    static buzzer_state oldstate = BUZZER_OFF;
+    uint32_t B, S; // length of beep and silence
+    if(buzzer == oldstate){ // keep current state
+        if(lastTms > Tms) return;
+        switch(buzzer){ // beep on/off
+            case BUZZER_LONG:
+                B = LONG_BUZZER_PERIOD;
+                S = LONG_BUZZER_PAUSE;
+                SEND("long ");
+            break;
+            case BUZZER_SHORT:
+                B = SHORT_BUZZER_PERIOD;
+                S = SHORT_BUZZER_PAUSE;
+                SEND("short ");
+            break;
+            default:
+            return;
+        }
+        if(CHK(BUZZER)){ // is ON
+            SEND("1->0\n");
+            OFF(BUZZER);
+            lastTms = Tms + S;
+        }else{ // is OFF
+            SEND("0->1\n");
+            ON(BUZZER);
+            lastTms = Tms + B;
+        }
+        sendbuf();
+        return;
+    }
+    SEND("New state: ");
+    switch(buzzer){ // change buzzer state
+        case BUZZER_ON:
+            ON(BUZZER);
+            SEND("on");
+        break;
+        case BUZZER_OFF:
+            OFF(BUZZER);
+            SEND("off");
+        break;
+        case BUZZER_LONG:
+            ON(BUZZER);
+            lastTms = Tms + LONG_BUZZER_PERIOD;
+            SEND("long");
+        break;
+        case BUZZER_SHORT:
+            ON(BUZZER);
+            lastTms = Tms + SHORT_BUZZER_PERIOD;
+            SEND("short");
+        break;
+    }
+    newline(); sendbuf();
+    oldstate = buzzer;
+}
 
 void exti4_15_isr(){
     EXTI->PR |= EXTI_PR_PR7; // clear pending bit
diff --git a/F0-nolib/Socket_fans/hardware.h b/F0-nolib/Socket_fans/hardware.h
index 8f76024..5f45d2d 100644
--- a/F0-nolib/Socket_fans/hardware.h
+++ b/F0-nolib/Socket_fans/hardware.h
@@ -61,16 +61,30 @@
 #define ON(x)           do{pin_set(x ## _port, x ## _pin);}while(0)
 #define OFF(x)          do{pin_clear(x ## _port, x ## _pin);}while(0)
 
+typedef enum{
+    BUZZER_OFF,     // buzzer is off
+    BUZZER_ON,      // continuous beeep
+    BUZZER_SHORT,   // short beeps with longer pause
+    BUZZER_LONG     // long beeps with shorter pause
+} buzzer_state;
+
+// Length of long and short time periods (ms)
+#define LONG_BUZZER_PERIOD      (4000)
+#define LONG_BUZZER_PAUSE       (6000)
+#define SHORT_BUZZER_PERIOD     (500)
+#define SHORT_BUZZER_PAUSE      (9500)
+
 extern volatile uint32_t Tms;
 extern volatile uint32_t Cooler0speed;
 extern volatile uint32_t Cooler1speed;
 extern volatile uint32_t Cooler1RPM;
-extern uint8_t ledsON;
+extern buzzer_state buzzer;
 
 void HW_setup(void);
 void adc_setup();
 void iwdg_setup();
 void pause_ms(uint32_t pause);
 void Jump2Boot();
+void buzzer_chk();
 
 #endif // __HARDWARE_H__
diff --git a/F0-nolib/Socket_fans/main.c b/F0-nolib/Socket_fans/main.c
index b6d86cd..645f69e 100644
--- a/F0-nolib/Socket_fans/main.c
+++ b/F0-nolib/Socket_fans/main.c
@@ -93,6 +93,7 @@ int main(void){
             IWDG->KR = IWDG_REFRESH;
             cmd_parser(txt);
         }
+        buzzer_chk();
     }
     return 0;
 }
diff --git a/F0-nolib/Socket_fans/proto.c b/F0-nolib/Socket_fans/proto.c
index eb899e8..e9fd16e 100644
--- a/F0-nolib/Socket_fans/proto.c
+++ b/F0-nolib/Socket_fans/proto.c
@@ -203,6 +203,30 @@ static inline void changeRPM(char *str){
     }
 }
 
+static inline void buzzercmd(char cmd){
+    SEND("Buzzer: ");
+    switch(cmd){
+        case '0':
+            buzzer = BUZZER_OFF;
+            SEND("off");
+        break;
+        case '1':
+            buzzer = BUZZER_ON;
+            SEND("on");
+        break;
+        case 'l':
+            buzzer = BUZZER_LONG;
+            SEND("long beeps");
+        break;
+        case 's':
+            buzzer = BUZZER_SHORT;
+            SEND("short beeps");
+        break;
+        default:
+            SEND("wrong command");
+    }
+}
+
 /**
  * @brief cmd_parser - command parsing
  * @param txt   - buffer with commands & data
@@ -226,6 +250,10 @@ void cmd_parser(char *txt){
             ADCget(txt[1]);
             goto eof;
         break;
+        case 'b': // buzzer
+            buzzercmd(txt[1]);
+            goto eof;
+        break;
         case 'C': // Cooler RPM
             coolerRPM(txt[1]);
             goto eof;
@@ -290,6 +318,7 @@ void cmd_parser(char *txt){
             "'Ax' - get ADC raw value (x=0..7)\n"
             "'a' - show current value of ADC1->DR\n"
             "'B' - buttons' state\n"
+            "'bx' - buzzer: x==0 - off, x==1 - on, x==l - long beeps, x==s - short beeps\n"
             "'Cx' - get cooler x (0/1) RPM\n"
             "'D' - activate DFU mode\n"
             "'M' - get MCU temperature\n"