diff --git a/flash.c b/flash.c
index 3ac53fb..a24f6c2 100644
--- a/flash.c
+++ b/flash.c
@@ -22,7 +22,8 @@
 #include "nanovna.h"
 #include <string.h>
 
-int16_t lastsaveid = 0;
+uint16_t lastsaveid = 0;
+static uint32_t checksum_ok = 0;
 
 static int flash_wait_for_last_operation(void)
 {
@@ -42,80 +43,71 @@ static void flash_erase_page0(uint32_t page_address)
   FLASH->CR &= ~FLASH_CR_PER;
 }
 
-int flash_erase_page(uint32_t page_address)
+static void flash_erase_page(uint32_t page_address)
 {
   chSysLock();
   flash_erase_page0(page_address);
   chSysUnlock();
-  return 0;
 }
 
-void flash_program_half_word(uint32_t address, uint16_t data)
-{
-  flash_wait_for_last_operation();
-  FLASH->CR |= FLASH_CR_PG;
-  *(__IO uint16_t*)address = data;
-  flash_wait_for_last_operation();
-  FLASH->CR &= ~FLASH_CR_PG;
-}
-
-void flash_unlock(void)
+static inline void flash_unlock(void)
 {
   // unlock sequence
   FLASH->KEYR = 0x45670123;
   FLASH->KEYR = 0xCDEF89AB;
 }
 
+static void flash_program_half_word_buffer(uint16_t* dst, uint16_t *data, uint16_t size)
+{
+  uint32_t i;
+  flash_unlock();
+  // erase flash pages for buffer (aligned to FLASH_PAGESIZE)
+  for (i = 0; i < size; i+=FLASH_PAGESIZE)
+    flash_erase_page((uint32_t)dst + i);
+  // Save buffer
+  __IO uint16_t* p = dst;
+  for (i = 0; i < size/sizeof(uint16_t); i++){
+    flash_wait_for_last_operation();
+    FLASH->CR |= FLASH_CR_PG;
+    p[i] = data[i];
+    flash_wait_for_last_operation();
+    FLASH->CR &= ~FLASH_CR_PG;
+  }
+}
+
 static uint32_t
 checksum(const void *start, size_t len)
 {
   uint32_t *p = (uint32_t*)start;
-  uint32_t *tail = (uint32_t*)(start + len);
   uint32_t value = 0;
-  while (p < tail)
+  // align by sizeof(uint32_t)
+  len = (len + sizeof(uint32_t)-1)/sizeof(uint32_t);
+  while (len-- > 0)
     value = __ROR(value, 31) + *p++;
   return value;
 }
 
-const uint32_t save_config_area = SAVE_CONFIG_ADDR;
-
 int
 config_save(void)
 {
-  uint16_t *src = (uint16_t*)&config;
-  uint16_t *dst = (uint16_t*)save_config_area;
-  int count = sizeof(config_t) / sizeof(uint16_t);
-
+  // Apply magic word and calculate checksum
   config.magic = CONFIG_MAGIC;
   config.checksum = checksum(&config, sizeof config - sizeof config.checksum);
 
-  flash_unlock();
-
-  /* erase flash pages */
-  flash_erase_page((uint32_t)dst);
-
-  /* write to flahs */
-  while (count-- > 0) {
-    flash_program_half_word((uint32_t)dst, *src++);
-    dst++;
-  }
-
+  // write to flash
+  flash_program_half_word_buffer((uint16_t*)SAVE_CONFIG_ADDR, (uint16_t*)&config, sizeof(config_t));
   return 0;
 }
 
 int
 config_recall(void)
 {
-  const config_t *src = (const config_t*)save_config_area;
-  void *dst = &config;
+  const config_t *src = (const config_t*)SAVE_CONFIG_ADDR;
 
-  if (src->magic != CONFIG_MAGIC)
+  if (src->magic != CONFIG_MAGIC || checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
     return -1;
-  if (checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
-    return -1;
-
-  /* duplicated saved data onto sram to be able to modify marker/trace */
-  memcpy(dst, src, sizeof(config_t));
+  // duplicated saved data onto sram to be able to modify marker/trace
+  memcpy(&config, src, sizeof(config_t));
   return 0;
 }
 
@@ -124,33 +116,16 @@ caldata_save(uint32_t id)
 {
   if (id >= SAVEAREA_MAX)
     return -1;
-  uint16_t *src = (uint16_t*)&current_props;
-  uint16_t *dst;
-  int count = sizeof(properties_t) / sizeof(uint16_t);
-
-  dst = (uint16_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
 
+  // Apply magic word and calculate checksum
   current_props.magic = CONFIG_MAGIC;
-  current_props.checksum = checksum(
-      &current_props, sizeof current_props - sizeof current_props.checksum);
+  current_props.checksum = checksum(&current_props, sizeof current_props - sizeof current_props.checksum);
 
-  flash_unlock();
+  // write to flash
+  uint16_t *dst = (uint16_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
+  flash_program_half_word_buffer(dst, (uint16_t*)&current_props, sizeof(properties_t));
 
-  /* erase flash pages */
-  void *p = dst;
-  void *tail = p + sizeof(properties_t);
-  while (p < tail) {
-    flash_erase_page((uint32_t)p);
-    p += FLASH_PAGESIZE;
-  }
-
-  /* write to flahs */
-  while (count-- > 0) {
-    flash_program_half_word((uint32_t)dst, *src++);
-    dst++;
-  }
-
-  /* after saving data, make active configuration points to flash */
+  // after saving data, make active configuration points to flash
   active_props = (properties_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
   lastsaveid = id;
 
@@ -162,56 +137,50 @@ caldata_recall(uint32_t id)
 {
   if (id >= SAVEAREA_MAX)
     return -1;
-  properties_t *src;
-  void *dst = &current_props;
-
   // point to saved area on the flash memory
-  src = (properties_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
+  properties_t *src = (properties_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
 
-  if (src->magic != CONFIG_MAGIC)
-    goto load_default;
-  if (checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
+  if (src->magic != CONFIG_MAGIC || checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
     goto load_default;
 
-  /* active configuration points to save data on flash memory */
+  // active configuration points to save data on flash memory
   active_props = src;
   lastsaveid = id;
 
-  /* duplicated saved data onto sram to be able to modify marker/trace */
-  memcpy(dst, src, sizeof(properties_t));
+  // duplicated saved data onto sram to be able to modify marker/trace
+  memcpy(&current_props, src, sizeof(properties_t));
   return 0;
 load_default:
   load_default_properties();
-  return -1;
+  return lastsaveid;
 }
 
+// Used in interpolate
 const properties_t *
-caldata_ref(uint32_t id)
+caldata_reference(void)
 {
-  if (id >= SAVEAREA_MAX)
+  if (lastsaveid >= SAVEAREA_MAX)
     return NULL;
   const properties_t *src;
 
-  src = (const properties_t*)(SAVE_PROP_CONFIG_ADDR + id * SAVE_PROP_CONFIG_SIZE);
-
-  if (src->magic != CONFIG_MAGIC)
-    return NULL;
-  if (checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
+  src = (const properties_t*)(SAVE_PROP_CONFIG_ADDR + lastsaveid * SAVE_PROP_CONFIG_SIZE);
+  // Check crc cache mask (made it only 1 time)
+  if (checksum_ok&(1<<lastsaveid))
+    return src;
+  if (src->magic != CONFIG_MAGIC || checksum(src, sizeof *src - sizeof src->checksum) != src->checksum)
     return NULL;
+  checksum_ok|=1<<lastsaveid;
   return src;
 }
 
 void
 clear_all_config_prop_data(void)
 {
+  uint32_t i;
   flash_unlock();
 
-  /* erase flash pages */
-  void *p = (void*)save_config_area;
-  void *tail = p + SAVE_FULL_AREA_SIZE;
-  while (p < tail) {
-    flash_erase_page((uint32_t)p);
-    p += FLASH_PAGESIZE;
-  }
+  // erase flash pages
+  for (i = 0; i < SAVE_FULL_AREA_SIZE; i+=FLASH_PAGESIZE)
+    flash_erase_page(SAVE_CONFIG_ADDR + i);
 }
 
diff --git a/main.c b/main.c
index e0341a1..bdb01aa 100644
--- a/main.c
+++ b/main.c
@@ -83,13 +83,15 @@ static volatile vna_shellcmd_t  shell_function = 0;
 //#define ENABLE_PORT_COMMAND
 // Enable si5351 timing command, used for debug
 #define ENABLE_SI5351_TIMINGS
+// Enable i2c timing command, used for debug
+#define ENABLE_I2C_TIMINGS
 
 static void apply_CH0_error_term_at(int i);
 static void apply_CH1_error_term_at(int i);
 static void apply_edelay(void);
 
 static uint16_t get_sweep_mode(void);
-static void cal_interpolate(int s);
+static void cal_interpolate(void);
 static void update_frequencies(bool interpolate);
 static void set_frequencies(uint32_t start, uint32_t stop, uint16_t points);
 static bool sweep(bool break_on_operation, uint16_t sweep_mode);
@@ -985,7 +987,7 @@ VNA_SHELL_FUNCTION(cmd_scan)
   }
   set_frequencies(start, stop, points);
   if (cal_status & CALSTAT_APPLY)
-    cal_interpolate(lastsaveid);
+    cal_interpolate();
   pause_sweep();
   sweep(false, sweep_mode);
   // Output data after if set (faster data recive)
@@ -1062,7 +1064,7 @@ update_frequencies(bool interpolate)
   // set grid layout
   update_grid();
   if (interpolate)
-    cal_interpolate(lastsaveid);
+    cal_interpolate();
   RESET_SWEEP;
 }
 
@@ -1510,9 +1512,9 @@ cal_done(void)
 }
 
 static void
-cal_interpolate(int s)
+cal_interpolate(void)
 {
-  const properties_t *src = caldata_ref(s);
+  const properties_t *src = caldata_reference();
   uint32_t i, j;
   int eterm;
   if (src == NULL)
@@ -2174,8 +2176,17 @@ VNA_SHELL_FUNCTION(cmd_vbat_offset)
 VNA_SHELL_FUNCTION(cmd_si5351time)
 {
   (void)argc;
-//  si5351_set_timing(my_atoui(argv[0]), my_atoui(argv[1]));
+  int idx = my_atoui(argv[0]);
+  uint16_t value = my_atoui(argv[1]);
+  si5351_set_timing(idx, value);
+}
+#endif
 
+
+#ifdef ENABLE_I2C_TIMINGS
+VNA_SHELL_FUNCTION(cmd_i2ctime)
+{
+  (void)argc;
   uint32_t tim =  STM32_TIMINGR_PRESC(0U)  |
                   STM32_TIMINGR_SCLDEL(my_atoui(argv[0])) | STM32_TIMINGR_SDADEL(my_atoui(argv[1])) |
                   STM32_TIMINGR_SCLH(my_atoui(argv[2])) | STM32_TIMINGR_SCLL(my_atoui(argv[3]));
@@ -2384,6 +2395,9 @@ static const VNAShellCommand commands[] =
 #endif
 #ifdef ENABLE_SI5351_TIMINGS
     {"t"           , cmd_si5351time  , CMD_WAIT_MUTEX},
+#endif
+#ifdef ENABLE_I2C_TIMINGS
+    {"i"           , cmd_i2ctime     , CMD_WAIT_MUTEX},
 #endif
     {NULL          , NULL            , 0}
 };
@@ -2531,10 +2545,10 @@ static const I2CConfig i2ccfg = {
 //  STM32_TIMINGR_PRESC(5U)  |
 //  STM32_TIMINGR_SCLDEL(3U) | STM32_TIMINGR_SDADEL(3U) |
 //  STM32_TIMINGR_SCLH(3U)   | STM32_TIMINGR_SCLL(9U),
-  // 600kHz @ SYSCLK 48MHz, manually get values, x1.5 I2C speed, but need calc timings
-  STM32_TIMINGR_PRESC(3U)  |
-  STM32_TIMINGR_SCLDEL(2U) | STM32_TIMINGR_SDADEL(2U) |
-  STM32_TIMINGR_SCLH(4U)   | STM32_TIMINGR_SCLL(4U),
+  // 600kHz @ SYSCLK 48MHz, manually get values, x1.5 I2C speed
+  STM32_TIMINGR_PRESC(0U)  |
+  STM32_TIMINGR_SCLDEL(10U) | STM32_TIMINGR_SDADEL(10U) |
+  STM32_TIMINGR_SCLH(30U)   | STM32_TIMINGR_SCLL(50U),
 #else
 #error "Need Define STM32_I2C1SW and set correct TIMINGR settings"
 #endif
diff --git a/mcuconf.h b/mcuconf.h
index 8c8842a..ccf17cc 100644
--- a/mcuconf.h
+++ b/mcuconf.h
@@ -52,7 +52,6 @@
 #define STM32_ADCSW                         STM32_ADCSW_HSI14
 #define STM32_ADCPRE                        STM32_ADCPRE_DIV4
 #define STM32_MCOSEL                        STM32_MCOSEL_PLLDIV2
-#define STM32_ADCPRE                        STM32_ADCPRE_DIV4
 #define STM32_ADCSW                         STM32_ADCSW_HSI14
 #define STM32_USBSW                         STM32_USBSW_HSI48
 #define STM32_CECSW                         STM32_CECSW_HSI
diff --git a/nanovna.h b/nanovna.h
index 1450917..215e2e0 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -41,8 +41,7 @@
 #define FREQUENCY_OFFSET         8000
 // Frequency offset for 48k ADC (sin_cos table in dsp.c generated for 3k, 4k, 5k, 6k, if change need create new table )
 //#define FREQUENCY_OFFSET         5000
-// Apply calibration after made sweep, if set to 1, calibration move out from sweep cycle
-// On fast CPU it slow down sweep, on slow CPU can made faster (not need wait additional measure time)
+// Apply calibration after made sweep, (if set 1, then calibration move out from sweep cycle)
 #define APPLY_CALIBRATION_AFTER_SWEEP 0
 // Use real time build table (undef for use constant)
 //#define USE_VARIABLE_OFFSET
@@ -131,8 +130,9 @@ extern const char *info_about[];
 /*
  * dsp.c
  */
-// Define aic3204 source clock frequency (for 8MHz used fractional multiplier, and possible little phase error)
+// Define aic3204 source clock frequency (on 8MHz used fractional multiplier, and possible little phase error)
 #define AUDIO_CLOCK_REF       ( 8000000U)
+// Define aic3204 source clock frequency (on 10752000U used integer multiplier)
 //#define AUDIO_CLOCK_REF       (10752000U)
 // Disable AIC PLL clock, use input as CODEC_CLKIN (not stable on some devices, on long work)
 //#define AUDIO_CLOCK_REF       (86016000U)
@@ -200,6 +200,8 @@ void tlv320aic3204_write_reg(uint8_t page, uint8_t reg, uint8_t data);
 #define LCD_WIDTH                   320
 #define LCD_HEIGHT                  240
 
+// Used marker size settings
+#define _USE_BIG_MARKER_     0
 // Used font settings
 #define _USE_FONT_           0
 
@@ -226,7 +228,8 @@ extern const uint8_t x7x11b_bits[];
 #elif _USE_FONT_ == 2
 extern const uint8_t x10x14_bits[];
 #define FONT_START_CHAR   0x17
-#define FONT_MAX_WIDTH      12
+#define FONT_MAX_WIDTH      14
+#define FONT_WIDTH          11
 #define FONT_GET_HEIGHT     14
 #define FONT_STR_HEIGHT     16
 #define FONT_GET_DATA(ch)   (   &x10x14_bits[(ch-FONT_START_CHAR)*2*FONT_GET_HEIGHT  ])
@@ -287,6 +290,7 @@ extern int16_t area_height;
 #define NUM_INPUT_HEIGHT   32
 
 // On screen keyboard button size
+// Use full screen keyboard
 #if 1
 #define KP_WIDTH                  ((LCD_WIDTH) / 4)                     // numeric keypad button width
 #define KP_HEIGHT                 ((LCD_HEIGHT - NUM_INPUT_HEIGHT) / 4) // numeric keypad button height
@@ -294,6 +298,7 @@ extern int16_t area_height;
 #define KP_GET_X(posx)            ((posx) * KP_WIDTH)                   // numeric keypad left
 #define KP_GET_Y(posy)            ((posy) * KP_HEIGHT)                  // numeric keypad top
 #else
+// Use less size keyboard
 #define KP_WIDTH     48
 #define KP_HEIGHT    48
 // Key x, y position (0 - 15) on screen
@@ -555,7 +560,7 @@ void rtc_set_time(uint32_t dr, uint32_t tr);
 
 #define CONFIG_MAGIC 0x434f4e45 /* 'CONF' */
 
-extern int16_t lastsaveid;
+extern uint16_t lastsaveid;
 
 #define frequency0 current_props._frequency0
 #define frequency1 current_props._frequency1
@@ -578,7 +583,7 @@ extern int16_t lastsaveid;
 
 int caldata_save(uint32_t id);
 int caldata_recall(uint32_t id);
-const properties_t *caldata_ref(uint32_t id);
+const properties_t *caldata_reference(void);
 
 int config_save(void);
 int config_recall(void);
diff --git a/plot.c b/plot.c
index df89d8f..0904e44 100644
--- a/plot.c
+++ b/plot.c
@@ -967,7 +967,7 @@ static const uint8_t reference_bitmap[]={
   _BMP8(0b11000000),
 };
 
-#if _USE_FONT_ == 0
+#if _USE_BIG_MARKER_ == 0
 #define MARKER_WIDTH       7
 #define MARKER_HEIGHT     10
 #define X_MARKER_OFFSET    3
@@ -1031,7 +1031,7 @@ static const uint8_t marker_bitmap[]={
   _BMP8(0b00000000),
 };
 
-#elif _USE_FONT_ == 1
+#elif _USE_BIG_MARKER_ == 1
 #define MARKER_WIDTH       10
 #define MARKER_HEIGHT      13
 #define X_MARKER_OFFSET     4