diff --git a/GUI/Calendar.c b/GUI/Calendar.c
index b9e1ca1..c7734b3 100644
--- a/GUI/Calendar.c
+++ b/GUI/Calendar.c
@@ -4,11 +4,7 @@
 #include "Calendar.h"
 #include "nrf_log.h"
 
-#if defined(S112)
-#define PAGE_HEIGHT 150
-#else
-#define PAGE_HEIGHT 64
-#endif
+#define PAGE_HEIGHT ((__HEAP_SIZE / 50) - 4)
 
 #define GFX_printf_styled(gfx, fg, bg, font, ...) \
             GFX_setTextColor(gfx, fg, bg);        \
diff --git a/Keil/EPD-nRF51.uvprojx b/Keil/EPD-nRF51.uvprojx
index 7c75362..1ecaf79 100644
--- a/Keil/EPD-nRF51.uvprojx
+++ b/Keil/EPD-nRF51.uvprojx
@@ -338,7 +338,7 @@
             <v6Rtti>0</v6Rtti>
             <VariousControls>
               <MiscControls></MiscControls>
-              <Define>BLE_STACK_SUPPORT_REQD NRF51822 NRF_SD_BLE_API_VERSION=2 S130 NRF51 SOFTDEVICE_PRESENT SWI_DISABLE0</Define>
+              <Define>BLE_STACK_SUPPORT_REQD NRF51822 NRF_SD_BLE_API_VERSION=2 S130 NRF51 SOFTDEVICE_PRESENT SWI_DISABLE0 __HEAP_SIZE=4096 __STACK_SIZE=2048</Define>
               <Undefine></Undefine>
               <IncludePath>..\config;..\EPD;..\GUI;..\SDK\12.3.0_d7731ad;..\SDK\12.3.0_d7731ad\components\toolchain;..\SDK\12.3.0_d7731ad\components\toolchain\cmsis\include;..\SDK\12.3.0_d7731ad\components\drivers_nrf\clock;..\SDK\12.3.0_d7731ad\components\drivers_nrf\common;..\SDK\12.3.0_d7731ad\components\drivers_nrf\delay;..\SDK\12.3.0_d7731ad\components\drivers_nrf\gpiote;..\SDK\12.3.0_d7731ad\components\drivers_nrf\hal;..\SDK\12.3.0_d7731ad\components\drivers_nrf\spi_master;..\SDK\12.3.0_d7731ad\components\drivers_nrf\twi_master;..\SDK\12.3.0_d7731ad\external\segger_rtt;..\SDK\12.3.0_d7731ad\components\libraries\fds;..\SDK\12.3.0_d7731ad\components\libraries\fstorage;..\SDK\12.3.0_d7731ad\components\libraries\experimental_section_vars;..\SDK\12.3.0_d7731ad\components\libraries\log;..\SDK\12.3.0_d7731ad\components\libraries\log\src;..\SDK\12.3.0_d7731ad\components\libraries\pwr_mgmt;..\SDK\12.3.0_d7731ad\components\libraries\scheduler;..\SDK\12.3.0_d7731ad\components\libraries\trace;..\SDK\12.3.0_d7731ad\components\libraries\timer;..\SDK\12.3.0_d7731ad\components\libraries\util;..\SDK\12.3.0_d7731ad\components\ble\common;..\SDK\12.3.0_d7731ad\components\ble\ble_advertising;..\SDK\12.3.0_d7731ad\components\softdevice\common\softdevice_handler;..\SDK\12.3.0_d7731ad\components\softdevice\s130\headers;..\SDK\12.3.0_d7731ad\components\softdevice\s130\headers\nrf51</IncludePath>
             </VariousControls>
@@ -356,7 +356,7 @@
             <ClangAsOpt>1</ClangAsOpt>
             <VariousControls>
               <MiscControls></MiscControls>
-              <Define>BLE_STACK_SUPPORT_REQD NRF51822 NRF_SD_BLE_API_VERSION=2 S130 NRF51 SOFTDEVICE_PRESENT SWI_DISABLE0</Define>
+              <Define>BLE_STACK_SUPPORT_REQD NRF51822 NRF_SD_BLE_API_VERSION=2 S130 NRF51 SOFTDEVICE_PRESENT SWI_DISABLE0 __HEAP_SIZE=4096 __STACK_SIZE=2048</Define>
               <Undefine></Undefine>
               <IncludePath>..\config;..\EPD;..\GUI;..\SDK\12.3.0_d7731ad;..\SDK\12.3.0_d7731ad\components\toolchain;..\SDK\12.3.0_d7731ad\components\toolchain\cmsis\include;..\SDK\12.3.0_d7731ad\components\drivers_nrf\clock;..\SDK\12.3.0_d7731ad\components\drivers_nrf\common;..\SDK\12.3.0_d7731ad\components\drivers_nrf\delay;..\SDK\12.3.0_d7731ad\components\drivers_nrf\gpiote;..\SDK\12.3.0_d7731ad\components\drivers_nrf\hal;..\SDK\12.3.0_d7731ad\components\drivers_nrf\spi_master;..\SDK\12.3.0_d7731ad\components\drivers_nrf\twi_master;..\SDK\12.3.0_d7731ad\external\segger_rtt;..\SDK\12.3.0_d7731ad\components\libraries\fds;..\SDK\12.3.0_d7731ad\components\libraries\fstorage;..\SDK\12.3.0_d7731ad\components\libraries\experimental_section_vars;..\SDK\12.3.0_d7731ad\components\libraries\log;..\SDK\12.3.0_d7731ad\components\libraries\log\src;..\SDK\12.3.0_d7731ad\components\libraries\pwr_mgmt;..\SDK\12.3.0_d7731ad\components\libraries\scheduler;..\SDK\12.3.0_d7731ad\components\libraries\trace;..\SDK\12.3.0_d7731ad\components\libraries\timer;..\SDK\12.3.0_d7731ad\components\libraries\util;..\SDK\12.3.0_d7731ad\components\ble\common;..\SDK\12.3.0_d7731ad\components\ble\ble_advertising;..\SDK\12.3.0_d7731ad\components\softdevice\common\softdevice_handler;..\SDK\12.3.0_d7731ad\components\softdevice\s130\headers;..\SDK\12.3.0_d7731ad\components\softdevice\s130\headers\nrf51</IncludePath>
             </VariousControls>
diff --git a/Makefile.nRF51 b/Makefile.nRF51
index e970a36..0b21bfa 100644
--- a/Makefile.nRF51
+++ b/Makefile.nRF51
@@ -118,6 +118,11 @@ LDFLAGS += -Wl,--gc-sections
 # use newlib in nano version
 LDFLAGS += --specs=nano.specs -lc -lnosys
 
+nrf51822_xxaa: CFLAGS += -D__HEAP_SIZE=4096
+nrf51822_xxaa: CFLAGS += -D__STACK_SIZE=2048
+nrf51822_xxaa: ASMFLAGS += -D__HEAP_SIZE=4096
+nrf51822_xxaa: ASMFLAGS += -D__STACK_SIZE=2048
+
 
 .PHONY: $(TARGETS) default all clean help flash flash_softdevice
 
diff --git a/SDK/12.3.0_d7731ad/components/toolchain/arm/arm_startup_nrf51.s b/SDK/12.3.0_d7731ad/components/toolchain/arm/arm_startup_nrf51.s
index 4f76255..fde9487 100644
--- a/SDK/12.3.0_d7731ad/components/toolchain/arm/arm_startup_nrf51.s
+++ b/SDK/12.3.0_d7731ad/components/toolchain/arm/arm_startup_nrf51.s
@@ -46,7 +46,7 @@ Heap_Size       EQU __STARTUP_CONFIG_HEAP_SIZE
                 ELIF :DEF: __HEAP_SIZE
 Heap_Size       EQU __HEAP_SIZE
                 ELSE
-Heap_Size       EQU     3600
+Heap_Size       EQU     2048
                 ENDIF
 
                 AREA    HEAP, NOINIT, READWRITE, ALIGN=3