diff --git a/F3:F303/NitrogenFlooding/ADUvsR b/F3:F303/NitrogenFlooding/ADUvsR
new file mode 100644
index 0000000..2432c8d
--- /dev/null
+++ b/F3:F303/NitrogenFlooding/ADUvsR
@@ -0,0 +1,34 @@
+1. interchannel difference (with ommeter influence)
+
+Rx	0	1	2	3	4	5	6	7	8	9
+106	388	387	387	386	385	385	386	384	384	384
+425	1064	1063	1064	1064	1063	1064	1063	1063	1062	1062
+1001	1471	1470	1469	1471	1470	1469	1471	1470	1469	1469
+2500	1763	1765	1765	1763	1765	1763	1763	1762	1763	1763
+5020	1888	1888	1888	1888	1889	1888	1889	1888	1890	1889
+1007	1958	1956	1957	1958	1959	1956	1957	1956	1957	1956
+
+2. ADU vs R (pure: without ommeter influence)
+Rx	ADU
+44	173
+103	380
+143	507
+236	778
+356	1073
+481	1329
+723	1718
+814	1836
+913	1952
+1010	2056
+1145	2181
+1340	2341
+1519	2464
+1701	2574
+2040	2745
+2910	3046
+3760	3231
+4710	3373
+5960	3502
+7420	3603
+8600	3663
+10060	3720
\ No newline at end of file
diff --git a/F3:F303/NitrogenFlooding/buttons.c b/F3:F303/NitrogenFlooding/buttons.c
index a1a0231..4344fcd 100644
--- a/F3:F303/NitrogenFlooding/buttons.c
+++ b/F3:F303/NitrogenFlooding/buttons.c
@@ -61,7 +61,7 @@ void process_keys(){
                 }
             }
         }
-        if(e != k->event){
+        if(e != k->event || e == EVT_HOLD){
             k->lastTms = Tms;
             lastUnsleep = Tms;
         }
diff --git a/F3:F303/NitrogenFlooding/hardware.h b/F3:F303/NitrogenFlooding/hardware.h
index fee3b5e..a1eaebc 100644
--- a/F3:F303/NitrogenFlooding/hardware.h
+++ b/F3:F303/NitrogenFlooding/hardware.h
@@ -86,11 +86,15 @@
 // refresh interval for screen windows
 #define WINDOW_REFRESH_TIMEOUT  (1000)
 
+typedef uint16_t btnevtmask; // event mask: less 8 - press, high 8 - hold
 // buttons masks bit0 - button0 etc
 #define BTN_ESC_MASK    (1<<0)
 #define BTN_LEFT_MASK   (1<<1)
 #define BTN_RIGHT_MASK  (1<<2)
 #define BTN_SEL_MASK    (1<<3)
+#define BTN_PRESS(e, mask)  ((e) & (mask))
+#define BTN_HOLD(e, mask)   ((e) & ((mask) << 8))
+#define BTN_PRESSHOLD(e, mask)  ((e) & ((mask) | ((mask)<<8)))
 
 // global sensors' data
 extern float Temperature, Pressure, Humidity, Dewpoint;
diff --git a/F3:F303/NitrogenFlooding/indication.c b/F3:F303/NitrogenFlooding/indication.c
index c61d0d3..1bbbdf6 100644
--- a/F3:F303/NitrogenFlooding/indication.c
+++ b/F3:F303/NitrogenFlooding/indication.c
@@ -40,8 +40,8 @@ static uint32_t ledT[LEDS_AMOUNT] = {0};
 static uint32_t ledH[LEDS_AMOUNT] = {199, 0, 0, 0};
 static uint32_t ledL[LEDS_AMOUNT] = {799, 1, 1, 1};
 
-static void refresh_mainwin(uint8_t evtmask);
-static void refresh_menu(uint8_t evtmask);
+static void refresh_mainwin(btnevtmask evtmask);
+static void refresh_menu(btnevtmask evtmask);
 
 // current menu
 static menu *curmenu = &mainmenu;
@@ -81,17 +81,17 @@ TRUE_INLINE void leds_proc(){
     }
 }
 
-static void refresh_mainwin(uint8_t evtmask){ // ask all parameters and refresh main window with new values
-    if(evtmask & BTN_ESC_MASK){ // force refresh
+static void refresh_mainwin(btnevtmask evtmask){ // ask all parameters and refresh main window with new values
+    if(BTN_PRESS(evtmask, BTN_ESC_MASK)){ // force refresh
         Sens_measured_time = Tms - SENSORS_DATA_TIMEOUT*2; // force refresh
         lastTupd = Tms;
         return; // just start measurements
     }
-    if(evtmask & BTN_SEL_MASK){ // switch to menu
+    if(BTN_PRESS(evtmask, BTN_SEL_MASK)){ // switch to menu
         init_menu(&mainmenu);
         return;
     }
-    if(evtmask) return; // left/right buttons - do nothing
+    if(evtmask) return; // left/right buttons press, any hold - do nothing
     cls();
     SetFontScale(1); // small menu items labels
     setBGcolor(COLOR_BLACK); setFGcolor(COLOR_LIGHTGREEN);
@@ -141,19 +141,19 @@ void init_menu(menu *m){
     refresh_menu(0);
 }
 
-static void refresh_menu(uint8_t evtmask){ // refresh menu with changed selection
+static void refresh_menu(btnevtmask evtmask){ // refresh menu with changed selection
     DBG("REFRESH menu");
     if(!curmenu){
         init_window(refresh_mainwin);
         return;
     }
-    if(evtmask & BTN_ESC_MASK){ // escape to level upper or to main window
+    if(BTN_PRESS(evtmask, BTN_ESC_MASK)){ // escape to level upper or to main window
         if(curmenu) curmenu = curmenu->parent;
         if(!curmenu){
             init_window(refresh_mainwin);
             return;
         }
-    } else if(evtmask & BTN_SEL_MASK){
+    } else if(BTN_PRESS(evtmask, BTN_SEL_MASK)){
         menuitem *selitem = &curmenu->items[curmenu->selected];
         menu *sub = selitem->submenu;
         void (*action)() = selitem->action;
@@ -161,9 +161,9 @@ static void refresh_menu(uint8_t evtmask){ // refresh menu with changed selectio
         if(sub){ // change to submenu
             curmenu = sub;
         } else return;
-    } else if(evtmask & BTN_LEFT_MASK){ // up
+    } else if(BTN_PRESSHOLD(evtmask, BTN_LEFT_MASK)){ // up
         if(curmenu->selected) --curmenu->selected;
-    } else if(evtmask & BTN_RIGHT_MASK){ // down
+    } else if(BTN_PRESSHOLD(evtmask, BTN_RIGHT_MASK)){ // down
         if(curmenu->selected < curmenu->nitems - 1) ++curmenu->selected;
     }
     cls();
@@ -198,15 +198,21 @@ static void refresh_menu(uint8_t evtmask){ // refresh menu with changed selectio
  * 2 - down
  * 3 - select/menu
  */
-TRUE_INLINE uint8_t btns_proc(){
+#if BTNSNO > 8
+#pragma error "Change this code!"
+#endif
+TRUE_INLINE btnevtmask btns_proc(){
     static uint32_t lastT = 0;
-    uint8_t evtmask = 0; // bitmask for active buttons (==1)
+    btnevtmask evtmask = 0; // bitmask for active buttons (==1)
     static keyevent lastevent[BTNSNO] = {0};
     if(lastUnsleep == lastT) return 0; // no buttons activity
     lastT = lastUnsleep;
     for(int i = 0; i < BTNSNO; ++i){
         keyevent evt = keystate(i, NULL); // T may be used for doubleclick detection
         if(evt == EVT_PRESS && lastevent[i] != EVT_PRESS) evtmask |= 1<<i;
+        if(evt == EVT_HOLD){
+            evtmask |= (0x100 << i);
+        }
         lastevent[i] = evt;
     }
     if(!evtmask) return 0;
@@ -219,7 +225,7 @@ void indication_process(){
     if(!LEDsON) return;
     leds_proc();
     if(ScrnState != SCREEN_RELAX) return; // dont process buttons when screen in updating state
-    uint8_t e = btns_proc();
+    btnevtmask e = btns_proc();
     if(dispstate == DISP_WINDOW){ // send refresh by timeout event
         if(e) lastTupd = Tms;
         else if(Tms - lastTupd > WINDOW_REFRESH_TIMEOUT){
diff --git a/F3:F303/NitrogenFlooding/menu.c b/F3:F303/NitrogenFlooding/menu.c
index 0165415..c9550f4 100644
--- a/F3:F303/NitrogenFlooding/menu.c
+++ b/F3:F303/NitrogenFlooding/menu.c
@@ -24,17 +24,26 @@
 #include "strfunc.h"
 #include "usb.h"
 
+#include <string.h>
+
 // integer parameter to change
 typedef struct{
-    uint32_t min;
-    uint32_t max;
-    uint32_t cur;
-    uint32_t *val;
-} u32par;
+    int32_t min;
+    int32_t max;
+    int32_t cur;
+    int32_t *val;
+} i32par_t;
+
+// function to run after selecting "yes" in yesno window
+typedef void (*yesfun_t)();
+yesfun_t yesfunction = NULL;
 
 // current parameter of uint32_t setter
-static u32par u32parameter = {0};
+static i32par_t i32parameter = {0};
 
+// string buffer for non-constant parname
+#define PARNMBUFSZ  (63)
+static char parnmbuff[PARNMBUFSZ+1];
 static const char *parname = NULL;
 
 // upper level menu to return from subwindow functions
@@ -43,6 +52,7 @@ static menu *uplevel = NULL;
 static void showadc(menu *m);
 static void htr1(menu *m);
 static void htr2(menu *m);
+static void savesettings(menu *m);
 
 static void testx(const char *text){
     USB_sendstr(text);
@@ -55,29 +65,28 @@ static void stest1(menu _U_ *m){testx("sub 1");}
 static void stest2(menu _U_ *m){testx("sub 2");}
 static void stest3(menu _U_ *m){testx("sub 3");}
 static void stest4(menu _U_ *m){testx("sub 4");}
-static void stest5(menu _U_ *m){testx("sub 5");}
 
 
-static menuitem submenu1items[] = {
+static menuitem settingsmenuitems[] = {
     {"test 1", NULL, stest1},
     {"test 2", NULL, stest2},
     {"test 3", NULL, stest3},
     {"test 4", NULL, stest4},
-    {"test 5", NULL, stest5},
+    {"Save", NULL, savesettings},
 };
 
-static menu submenu1 = {
+static menu settingsmenu = {
     .parent = &mainmenu,
     .nitems = 5,
     .selected = 0,
-    .items = submenu1items
+    .items = settingsmenuitems
 };
 
 static menuitem mainmenuitems[] = {
     {"ADC raw data", NULL, showadc},
     {"Heater1 power", NULL, htr1},
     {"Heater2 power", NULL, htr2},
-    {"Submenu1", &submenu1, NULL},
+    {"Settings", &settingsmenu, NULL},
     {"Test3", NULL, test3},
     {"Test4", NULL, test4},
 };
@@ -89,8 +98,8 @@ menu mainmenu = {
     .items = mainmenuitems
 };
 
-static void refresh_adcwin(uint8_t evtmask){
-    if(evtmask & BTN_ESC_MASK || evtmask & BTN_SEL_MASK){ // switch to menu
+static void refresh_adcwin(btnevtmask evtmask){
+    if(BTN_PRESS(evtmask, BTN_ESC_MASK | BTN_SEL_MASK)){ // switch to menu
         init_menu(uplevel);
         return;
     }
@@ -127,20 +136,28 @@ static void showadc(menu *m){
 }
 
 // window of uint32_t setter
-static void refresh_u32setter(uint8_t evtmask){
+static void refresh_i32setter(btnevtmask evtmask){
     int selected = 0;
-    if(evtmask & BTN_ESC_MASK){ // return to main menu
+    if(BTN_PRESS(evtmask, BTN_ESC_MASK)){ // return to main menu
         init_menu(uplevel);
         return;
     }
     cls();
-    if(evtmask & BTN_SEL_MASK){ // change value
-        *u32parameter.val = u32parameter.cur;
+    int incrdecr = 0;
+    if(BTN_PRESS(evtmask, BTN_SEL_MASK)){ // change value
+        *i32parameter.val = i32parameter.cur;
         selected = 1;
-    } else if(evtmask & BTN_LEFT_MASK){ // decrement
-        if(u32parameter.cur > u32parameter.min) --u32parameter.cur;
-    } else if(evtmask & BTN_RIGHT_MASK){ // increment
-        if(u32parameter.cur < u32parameter.max) ++u32parameter.cur;
+    } else if(BTN_PRESSHOLD(evtmask, BTN_LEFT_MASK)){ // decrement
+        if(BTN_HOLD(evtmask, BTN_LEFT_MASK)) incrdecr = -3;
+        else incrdecr = -1;
+    } else if(BTN_PRESSHOLD(evtmask, BTN_RIGHT_MASK)){ // increment
+        if(BTN_HOLD(evtmask, BTN_RIGHT_MASK)) incrdecr = 3;
+        else incrdecr = 1;
+    }
+    if(incrdecr){
+        i32parameter.cur += incrdecr;
+        if(i32parameter.cur < i32parameter.min) i32parameter.cur = i32parameter.min;
+        if(i32parameter.cur > i32parameter.max) i32parameter.cur = i32parameter.max;
     }
     setFGcolor(COLOR_CHOCOLATE);
     SetFontScale(2);
@@ -150,18 +167,62 @@ static void refresh_u32setter(uint8_t evtmask){
     Y += fontheight + fontheight/2;
     if(selected) setFGcolor(COLOR_GREEN);
     else setFGcolor(COLOR_BLUE);
-    CenterStringAt(Y, u2str(u32parameter.cur));
+    CenterStringAt(Y, u2str(i32parameter.cur));
 }
 
 // init pwm setter
 static void showpwm(menu *m, int nccr){
-    u32parameter.max = 100;
-    u32parameter.min = 0;
-    u32parameter.cur = (nccr == 3) ? TIM3->CCR3 : TIM3->CCR4;
-    u32parameter.val = (nccr == 3) ? (uint32_t*) &TIM3->CCR3 : (uint32_t*) &TIM3->CCR4;
+    i32parameter.max = PWM_CCR_MAX;
+    i32parameter.min = 0;
+    i32parameter.cur = (nccr == 3) ? TIM3->CCR3 : TIM3->CCR4;
+    i32parameter.val = (nccr == 3) ? (int32_t*) &TIM3->CCR3 : (int32_t*) &TIM3->CCR4;
     parname = m->items[m->selected].text;
     uplevel = m;
-    init_window(refresh_u32setter);
+    init_window(refresh_i32setter);
 }
 static void htr1(menu *m){showpwm(m, 3);}
 static void htr2(menu *m){showpwm(m, 4);}
+
+
+static void refresh_yesno(btnevtmask evtmask){
+    if(BTN_PRESS(evtmask, BTN_ESC_MASK)){ // return to main menu
+        init_menu(uplevel);
+        return;
+    }
+    cls();
+    const char *msgs[] = {"No", "Yes"};
+    static int current = 0; // current item: "NO"
+    int selected = 0; // not selected
+    if(BTN_PRESS(evtmask, BTN_SEL_MASK)){ // change value
+        selected = 1;
+    } else if(BTN_PRESS(evtmask, BTN_LEFT_MASK | BTN_RIGHT_MASK)){
+        current = !current;
+    }
+    setFGcolor(COLOR_CHOCOLATE);
+    SetFontScale(2);
+    int Y = fontheight + fontheight/2;
+    CenterStringAt(Y, parname);
+    SetFontScale(3);
+    Y += fontheight + fontheight/2;
+    if(selected) setFGcolor(COLOR_GREEN);
+    else setFGcolor(COLOR_BLUE);
+    CenterStringAt(Y, msgs[current]);
+    if(selected && current == 1) yesfunction();
+}
+
+static void savesdummy(){
+    USB_sendstr("Settings saved\n");
+}
+// save current settings
+static void savesettings(menu *m){
+    yesfunction = savesdummy;
+    uplevel = m;
+    const char *p = m->items[m->selected].text;
+    int l = strlen(p);
+    if(l > PARNMBUFSZ-1) l = PARNMBUFSZ-1;
+    strncpy(parnmbuff, p, l);
+    parnmbuff[l] = '?';
+    parnmbuff[l+1] = 0;
+    parname = parnmbuff;
+    init_window(refresh_yesno);
+}
diff --git a/F3:F303/NitrogenFlooding/menu.h b/F3:F303/NitrogenFlooding/menu.h
index 6596fde..b9cc208 100644
--- a/F3:F303/NitrogenFlooding/menu.h
+++ b/F3:F303/NitrogenFlooding/menu.h
@@ -18,6 +18,8 @@
 
 #pragma once
 
+#include "hardware.h"
+
 #include <stdint.h>
 
 struct _menu_;
@@ -37,4 +39,4 @@ typedef struct _menu_{
 extern menu mainmenu;
 
 // subwindow handler
-typedef void (*window_handler)(uint8_t evtmask);
+typedef void (*window_handler)(btnevtmask evtmask);
diff --git a/F3:F303/NitrogenFlooding/nitrogen.bin b/F3:F303/NitrogenFlooding/nitrogen.bin
index c64dc54..890f77a 100755
Binary files a/F3:F303/NitrogenFlooding/nitrogen.bin and b/F3:F303/NitrogenFlooding/nitrogen.bin differ
diff --git a/F3:F303/NitrogenFlooding/proto.c b/F3:F303/NitrogenFlooding/proto.c
index 9b8532d..298e27d 100644
--- a/F3:F303/NitrogenFlooding/proto.c
+++ b/F3:F303/NitrogenFlooding/proto.c
@@ -161,9 +161,9 @@ static int adcon(const char *cmd, int _U_ parno, const char *c, int32_t i){
 static int adcval(const char *cmd, int parno, const char _U_ *c, int32_t i){
     if(parno >= NUMBER_OF_ADC_CHANNELS) return RET_WRONGPARNO;
     if(parno < 0){ // all channels
-        for(i = 0; i < NUMBER_OF_ADC_CHANNELS; ++i) sendkey(cmd, i, getADCval(i));
+        for(i = 0; i < NUMBER_OF_ADC_CHANNELS; ++i) sendkey(cmd, i, ADCvals[i]);
     }else
-        sendkey(cmd, parno, getADCval(parno));
+        sendkey(cmd, parno, ADCvals[i]);
     return RET_GOOD;
 }
 static int adcvoltage(const char *cmd, int parno, const char _U_ *c, int32_t i){
diff --git a/F3:F303/NitrogenFlooding/spi.c b/F3:F303/NitrogenFlooding/spi.c
index 0d13b16..9007842 100644
--- a/F3:F303/NitrogenFlooding/spi.c
+++ b/F3:F303/NitrogenFlooding/spi.c
@@ -133,7 +133,7 @@ int spi_read(uint8_t *data, uint32_t n){
         SPIDR = 0;
         WAITX(!(SPI2->SR & SPI_SR_RXNE));
         data[x] = SPIDR;
-        USB_sendstr("rd got "); USB_sendstr(uhex2str(data[x]));
+        //USB_sendstr("rd got "); USB_sendstr(uhex2str(data[x]));
         newline();
     }
     return 1;
diff --git a/F3:F303/NitrogenFlooding/version.inc b/F3:F303/NitrogenFlooding/version.inc
index fdeef24..4949b60 100644
--- a/F3:F303/NitrogenFlooding/version.inc
+++ b/F3:F303/NitrogenFlooding/version.inc
@@ -1,2 +1,2 @@
-#define BUILD_NUMBER "280"
+#define BUILD_NUMBER "294"
 #define BUILD_DATE "2023-05-14"