From 46a3ab60075bff3414d2bde0cedd3e7557a38164 Mon Sep 17 00:00:00 2001
From: true <trueserve@users.noreply.github.com>
Date: Sun, 25 Jun 2023 05:01:16 -0700
Subject: [PATCH] bootloader: flash page erase is on-demand, now fits in 2K

Flash pages are only erased as needed during the flash routine, which makes flashing faster as well as making the transfer consistent.

Later datasheets have the flash clock set to 2MHz. I've set it to 2MHz here. I may undo this change later depending on how slow loading a 14K firmware feels.

Was able to save enough space to reduce bootloader size from almost 2.5K to 2K exactly. Adjusted flash offsets to start from 0x800.

GPIO values are now mostly reset to power-on defaults.

Fixed some formatting. Removed dead code.
---
 bootloader_hk32f030m_uart_xmodem/.cproject    |   2 +-
 ...ootloader_hk32f030m_uart_xmodem_v0.0.2.bin | Bin 0 -> 2048 bytes
 ...ootloader_hk32f030m_uart_xmodem_v0.0.2.hex | 134 ++++++++++++++++++
 ...otloader_hk32f030m_uart_xmodem _dbg.launch |  10 +-
 .../code/inc/flash.h                          |   5 +-
 .../code/inc/usart.h                          |   4 +-
 .../code/inc/user_io.h                        |   1 -
 .../code/inc/xmodem.h                         |   4 +-
 .../code/src/flash.c                          |  75 ++++------
 .../code/src/main.c                           |  46 +++---
 .../code/src/usart.c                          |  76 ++--------
 .../code/src/user_io.c                        |  48 +++++--
 .../code/src/xmodem.c                         |  57 ++++----
 .../HK32F030M/Source/startup_hk32f030mf4p6.s  |  74 +++++-----
 .../CMSIS/HK32F030M/Source/system_hk32f030m.c |  49 +++----
 15 files changed, 336 insertions(+), 249 deletions(-)
 create mode 100644 bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.bin
 create mode 100644 bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.hex

diff --git a/bootloader_hk32f030m_uart_xmodem/.cproject b/bootloader_hk32f030m_uart_xmodem/.cproject
index c45870e..4d7db8e 100644
--- a/bootloader_hk32f030m_uart_xmodem/.cproject
+++ b/bootloader_hk32f030m_uart_xmodem/.cproject
@@ -22,7 +22,7 @@
 							<option id="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.target_coreid.241230391" name="Core" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.target_coreid" useByScannerDiscovery="false" value="0" valueType="string"/>
 							<option id="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.converthex.1728678093" name="Convert to Intel Hex file (-O ihex)" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.converthex" useByScannerDiscovery="false" value="true" valueType="boolean"/>
 							<option id="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.toolchain.698382755" name="Toolchain" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.toolchain" useByScannerDiscovery="false" value="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.toolchain.value.workspace" valueType="string"/>
-							<option id="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.convertbinary.1163999831" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.convertbinary" value="true" valueType="boolean"/>
+							<option id="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.convertbinary.1163999831" name="Convert to binary file (-O binary)" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.option.convertbinary" useByScannerDiscovery="false" value="true" valueType="boolean"/>
 							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF" id="com.st.stm32cube.ide.mcu.gnu.managedbuild.targetplatform.1731985094" isAbstract="false" osList="all" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.targetplatform"/>
 							<builder buildPath="${workspace_loc:/HK32F030}/Debug" id="com.st.stm32cube.ide.mcu.gnu.managedbuild.builder.2105898051" keepEnvironmentInBuildfile="false" managedBuildOn="true" name="Gnu Make Builder" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.builder"/>
 							<tool id="com.st.stm32cube.ide.mcu.gnu.managedbuild.tool.assembler.1554269278" name="MCU GCC Assembler" superClass="com.st.stm32cube.ide.mcu.gnu.managedbuild.tool.assembler">
diff --git a/bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.bin b/bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.bin
new file mode 100644
index 0000000000000000000000000000000000000000..5cd410c8c936e3e55f4e896fdc7b7cec1edf5038
GIT binary patch
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HcmV?d00001

diff --git a/bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.hex b/bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.hex
new file mode 100644
index 0000000..f78211f
--- /dev/null
+++ b/bootloader_hk32f030m_uart_xmodem/_bin/bootloader_hk32f030m_uart_xmodem_v0.0.2.hex
@@ -0,0 +1,134 @@
+:020000040800F2
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diff --git a/bootloader_hk32f030m_uart_xmodem/bootloader_hk32f030m_uart_xmodem _dbg.launch b/bootloader_hk32f030m_uart_xmodem/bootloader_hk32f030m_uart_xmodem _dbg.launch
index 42f2959..764fbfc 100644
--- a/bootloader_hk32f030m_uart_xmodem/bootloader_hk32f030m_uart_xmodem _dbg.launch	
+++ b/bootloader_hk32f030m_uart_xmodem/bootloader_hk32f030m_uart_xmodem _dbg.launch	
@@ -2,12 +2,13 @@
 <launchConfiguration type="com.st.stm32cube.ide.mcu.debug.launch.launchConfigurationType">
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.device" value="HK32F030MF4P6"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.endian" value="little"/>
-    <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.init_speed" value="4000"/>
+    <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.init_speed" value="2000"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.jlink_check_serial_number" value="false"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.jlink_script_path" value=""/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.jlink_script_used" value="false"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.jlink_txt_serial_number" value=""/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.reset_strategy" value="type_0_normal"/>
+    <stringAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.restart_configurations" value="{&quot;fVersion&quot;:1,&quot;fItems&quot;:[{&quot;fDisplayName&quot;:&quot;Type 0: Normal&quot;,&quot;fIsSuppressible&quot;:false,&quot;fResetAttribute&quot;:&quot;Type 0: Normal&quot;,&quot;fResetStrategies&quot;:[{&quot;fDisplayName&quot;:&quot;None&quot;,&quot;fLaunchAttribute&quot;:&quot;no_reset&quot;,&quot;fGdbCommands&quot;:[],&quot;fCmdOptions&quot;:[]},{&quot;fDisplayName&quot;:&quot;Type 0: Normal&quot;,&quot;fLaunchAttribute&quot;:&quot;type_0_normal&quot;,&quot;fGdbCommands&quot;:[&quot;monitor reset\r\n&quot;],&quot;fCmdOptions&quot;:[]}],&quot;fGdbCommandGroup&quot;:{&quot;name&quot;:&quot;Additional commands&quot;,&quot;commands&quot;:[]},&quot;fStartApplication&quot;:true}]}"/>
     <intAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.rtos_implementation" value="1"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.scan_chain_auto" value="true"/>
     <intAttribute key="com.st.stm32cube.ide.mcu.debug.jlink.scan_chain_irpre" value="0"/>
@@ -22,7 +23,7 @@
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.ip_address_local" value="localhost"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.launch.limit_swo_clock.enabled" value="false"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.limit_swo_clock.value" value=""/>
-    <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.loadList" value="{&quot;fItems&quot;:[{&quot;fIsFromMainTab&quot;:true,&quot;fPath&quot;:&quot;_dbg/hk32f030m_xmodem_bl.elf&quot;,&quot;fProjectName&quot;:&quot;bootloader_hk32f030m_uart_xmodem&quot;,&quot;fPerformBuild&quot;:true,&quot;fDownload&quot;:true,&quot;fLoadSymbols&quot;:true}]}"/>
+    <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.loadList" value="{&quot;fItems&quot;:[{&quot;fIsFromMainTab&quot;:true,&quot;fPath&quot;:&quot;_dbg/bootloader_hk32f030m_uart_xmodem.elf&quot;,&quot;fProjectName&quot;:&quot;bootloader_hk32f030m_uart_xmodem&quot;,&quot;fPerformBuild&quot;:true,&quot;fDownload&quot;:true,&quot;fLoadSymbols&quot;:true}]}"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.override_start_address_mode" value="default"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.remoteCommand" value="target extended-remote"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.launch.startServer" value="true"/>
@@ -34,7 +35,7 @@
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.swv_trace_hclk" value="8000000"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.launch.useRemoteTarget" value="true"/>
     <stringAttribute key="com.st.stm32cube.ide.mcu.debug.launch.vector_table" value=""/>
-    <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.launch.verify_flash_download" value="true"/>
+    <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.launch.verify_flash_download" value="false"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.stlink.cti_allow_halt" value="false"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.stlink.cti_signal_halt" value="false"/>
     <booleanAttribute key="com.st.stm32cube.ide.mcu.debug.stlink.enable_logging" value="false"/>
@@ -76,7 +77,7 @@
     <stringAttribute key="org.eclipse.cdt.launch.DEBUGGER_START_MODE" value="remote"/>
     <booleanAttribute key="org.eclipse.cdt.launch.DEBUGGER_STOP_AT_MAIN" value="true"/>
     <stringAttribute key="org.eclipse.cdt.launch.DEBUGGER_STOP_AT_MAIN_SYMBOL" value="main"/>
-    <stringAttribute key="org.eclipse.cdt.launch.PROGRAM_NAME" value="_dbg/hk32f030m_xmodem_bl.elf"/>
+    <stringAttribute key="org.eclipse.cdt.launch.PROGRAM_NAME" value="_dbg/bootloader_hk32f030m_uart_xmodem.elf"/>
     <stringAttribute key="org.eclipse.cdt.launch.PROJECT_ATTR" value="bootloader_hk32f030m_uart_xmodem"/>
     <booleanAttribute key="org.eclipse.cdt.launch.PROJECT_BUILD_CONFIG_AUTO_ATTR" value="true"/>
     <stringAttribute key="org.eclipse.cdt.launch.PROJECT_BUILD_CONFIG_ID_ATTR" value="com.st.stm32cube.ide.mcu.gnu.managedbuild.config.exe.debug.1673231411"/>
@@ -86,5 +87,6 @@
     <listAttribute key="org.eclipse.debug.core.MAPPED_RESOURCE_TYPES">
         <listEntry value="4"/>
     </listAttribute>
+    <stringAttribute key="org.eclipse.dsf.launch.MEMORY_BLOCKS" value="&lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot; standalone=&quot;no&quot;?&gt;&lt;memoryBlockExpressionList context=&quot;reserved-for-future-use&quot;/&gt;"/>
     <stringAttribute key="process_factory_id" value="com.st.stm32cube.ide.mcu.debug.launch.HardwareDebugProcessFactory"/>
 </launchConfiguration>
diff --git a/bootloader_hk32f030m_uart_xmodem/code/inc/flash.h b/bootloader_hk32f030m_uart_xmodem/code/inc/flash.h
index 8ab675e..7c430ec 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/inc/flash.h
+++ b/bootloader_hk32f030m_uart_xmodem/code/inc/flash.h
@@ -15,8 +15,9 @@
 
 #define FLASH_SIZE					16384								// size of overall flash available on MCU
 #define FLASH_ERASE_PAGE_SIZE   	((uint16_t)0x80)					// erase page size
+#define FLASH_ERASE_PAGE_MASK		0x7f								// bitmask of page size
 
-#define USER_APP_START_ADDR			((uint32_t)FLASH_BASE + 0xa00)		// 2560 bytes (20 pages) rsvd for bootloader
+#define USER_APP_START_ADDR			((uint32_t)FLASH_BASE + 0x800)		// 2048 bytes (16 pages) rsvd for bootloader
 #define USER_APP_END_ADDR			((uint32_t)FLASH_BASE + FLASH_SIZE)
 
 
@@ -32,7 +33,7 @@ typedef enum {
 
 
 
-BL_flash_status flash_erase_user_app();
+BL_flash_status flash_erase_page(uint32_t addr);
 BL_flash_status flash_write(uint32_t addr, uint8_t *data, uint16_t length);
 void jump_to_user_app();
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/inc/usart.h b/bootloader_hk32f030m_uart_xmodem/code/inc/usart.h
index c327542..8cb5716 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/inc/usart.h
+++ b/bootloader_hk32f030m_uart_xmodem/code/inc/usart.h
@@ -9,7 +9,7 @@
 #define CODE_INC_USART_H_
 
 
-#define COMM_TIMEOUT		512000;
+#define COMM_TIMEOUT		0xffff;
 
 
 
@@ -24,7 +24,7 @@ typedef enum {
 
 void comm_init();
 BL_comm_status comm_rx(uint8_t *data, uint16_t length);
-BL_comm_status comm_tx_str(uint8_t *data);
+BL_comm_status comm_tx_str(char *data);
 BL_comm_status comm_tx_byte(uint8_t data);
 
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/inc/user_io.h b/bootloader_hk32f030m_uart_xmodem/code/inc/user_io.h
index 45231d7..5808a18 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/inc/user_io.h
+++ b/bootloader_hk32f030m_uart_xmodem/code/inc/user_io.h
@@ -29,7 +29,6 @@
 
 void user_io_init();
 void user_led_init();
-void user_led_set(uint8_t lit);
 
 
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/inc/xmodem.h b/bootloader_hk32f030m_uart_xmodem/code/inc/xmodem.h
index 7cf11f6..c9029c2 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/inc/xmodem.h
+++ b/bootloader_hk32f030m_uart_xmodem/code/inc/xmodem.h
@@ -72,7 +72,9 @@ typedef enum {
   X_ERROR         = 0xFFu  /**< Generic error. */
 } BL_xmodem_status;
 
-void xmodem_receive(void);
+
+
+BL_xmodem_status xmodem_receive(void);
 
 
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/src/flash.c b/bootloader_hk32f030m_uart_xmodem/code/src/flash.c
index 3e61a87..e54b261 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/src/flash.c
+++ b/bootloader_hk32f030m_uart_xmodem/code/src/flash.c
@@ -11,49 +11,22 @@
 
 
 /**
- * @brief   This function erases the user application area, from start to end of flash.
+ * @brief   This function erases a single flash page.
  * @return  status: Report about the success of the erasing.
  */
-__attribute__ ((long_call, section(".ramfunc"))) BL_flash_status flash_erase_user_app()
+__attribute__ ((long_call, section(".ramfunc"))) BL_flash_status flash_erase_page(uint32_t addr)
 {
-	// uint32_t timeout;
-	uint32_t page;
+	BL_flash_status status = FLASH_ERROR;
 
 	FLASH_Unlock();
 
-	for (page = USER_APP_START_ADDR; page < USER_APP_END_ADDR; page += FLASH_ERASE_PAGE_SIZE) {
-		if (FLASH_ErasePage(page) != FLASH_COMPLETE) {
-			FLASH_Lock();
-			return FLASH_ERROR;
-		}
-
-		/*
-		// clear end of operation bit
-		FLASH->SR &= ~FLASH_FLAG_EOP;
-
-		// start erasing page
-	    FLASH->CR |= FLASH_CR_PER;
-	    FLASH->AR  = page;
-	    FLASH->CR |= FLASH_CR_STRT;
-
-	    // wait wait for operation to complete
-		timeout = FLASH_ER_PRG_TIMEOUT;
-		while ((FLASH->SR & FLASH_FLAG_BSY)) {
-			timeout--;
-			if (!timeout) {
-				FLASH_Lock();
-				return FLASH_ERROR;
-			}
-		}
-
-		// disable page erase bit
-		FLASH->CR &= ~FLASH_CR_PER;
-		*/
+	if (FLASH_ErasePage(addr) == FLASH_COMPLETE) {
+		status = FLASH_OK;
 	}
 
 	FLASH_Lock();
 
-	return FLASH_OK;
+	return status;
 }
 
 /**
@@ -71,23 +44,23 @@ __attribute__ ((long_call, section(".ramfunc"))) BL_flash_status flash_write(uin
 
 	/* Loop through the data. */
 	for (uint32_t i = 0u; (i < length) && (status == FLASH_OK); i++) {
-	  if (addr >= USER_APP_END_ADDR) {
-		  status = FLASH_ERROR_SIZE;
-		  break;
-	  } else {
-		  /* The actual flashing. If there is an error, then report it. */
-		  if (FLASH_ProgramByte(addr, data[i]) != FLASH_COMPLETE) {
-			  status |= FLASH_ERROR_WRITE;
-		  }
+		if (addr >= USER_APP_END_ADDR) {
+			status = FLASH_ERROR_SIZE;
+			break;
+		} else {
+			/* The actual flashing. If there is an error, then report it. */
+			if (FLASH_ProgramByte(addr, data[i]) != FLASH_COMPLETE) {
+				status |= FLASH_ERROR_WRITE;
+			}
 
-		  /* Read back the content of the memory. If it is wrong, then report an error. */
-		  if (data[i] != (*(volatile uint8_t *)addr)) {
-			  status |= FLASH_ERROR_VERIFY;
-		  }
+			/* Read back the content of the memory. If it is wrong, then report an error. */
+			if (data[i] != (*(volatile uint8_t *)addr)) {
+				status |= FLASH_ERROR_VERIFY;
+			}
 
-		  /* Shift the address by a word. */
-		  addr++;
-	  }
+			/* Shift the address by a word. */
+			addr++;
+		}
 	}
 
 	FLASH_Lock();
@@ -109,6 +82,12 @@ void jump_to_user_app()
 	USART1->CR1 = 0;
 	USART1->BRR = 0;
 
+	// configure GPIO back to default
+	GPIOA->PUPDR = (uint32_t)0xffff;	// although marked as reserved, it is the default per datasheet
+	GPIOA->MODER = (uint32_t)0xffff;
+	GPIOB->MODER = (uint32_t)0xfbff;
+	GPIOD->MODER = (uint32_t)0xfbff;
+
 	// disable configured interrupts
 	// NVIC->ICER[0] = 0;
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/src/main.c b/bootloader_hk32f030m_uart_xmodem/code/src/main.c
index f1ab262..4297186 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/src/main.c
+++ b/bootloader_hk32f030m_uart_xmodem/code/src/main.c
@@ -22,8 +22,8 @@
 
 int main(void)
 {
-	uint8_t btn;
-	//volatile uint16_t timeout = 0xffff;
+	uint32_t i;
+	uint32_t btn;
 
 	// ensure the bootloader is write protected
 	// TODO
@@ -31,9 +31,6 @@ int main(void)
 	// configure button and LED
 	user_io_init();
 
-	// need a small delay to ensure the button pullup/down will charge/discharge pin capacitance
-	//while (--timeout);
-
 	// get button state
 	btn = BTN_PORT->IDR & (1 << BTN_PIN);
 #if BTN_ACT_DIR == 0
@@ -41,34 +38,45 @@ int main(void)
 #endif
 
 	// bootloader activation methods
-	if (btn 																// button pushed
-			|| (*(volatile uint32_t *)USER_APP_START_ADDR) == 0x00000000	// flash empty
-			|| (*(volatile uint32_t *)USER_APP_START_ADDR) == 0xFFFFFFFF) {	// flash empty
-
-		// bootloader is activated, show it
+	i = *(volatile uint32_t *)USER_APP_START_ADDR;			// first byte of user flash
+	if (btn || (i == 0x00000000) || (i = 0xffffffff)) {		// is button pushed, or flash empty?
+		// bootloader is activated; configure systick to flash LED
 		user_led_init();
 
 		// configure serial comms and print welcome banner
 		// todo: implement autobaud?
 		comm_init();
 
-		const uint8_t *banner_bar = (uint8_t *)"\r\n================================================\r\n";
-		comm_tx_str((uint8_t *)banner_bar);
-		comm_tx_str((uint8_t *)"trueControl HK32F XMODEM Flash Bootloader v0.0.1");
-		comm_tx_str((uint8_t *)banner_bar);
+		comm_tx_byte('\r');
+		comm_tx_byte('\n');
+
+		for (i = 0; i < 31; i++) {
+			comm_tx_byte('=');
+		}
+
+		comm_tx_str("\r\ntrueControl HK32F Loader v0.0.2\r\n");
+
+		for (i = 0; i < 31; i++) {
+			comm_tx_byte('=');
+		}
 
 		// wait for firmware load or reset
 		while(1) {
-			comm_tx_str((uint8_t*)"\r\nsend binary file using XMODEM to update firmware");
-			comm_tx_str((uint8_t*)"\r\nthe first data block will take time. it's normal\r\n\r\n");
-			xmodem_receive();
+			// announce bootloader start
+			comm_tx_str("\r\n\r\nsend firmware file using XMODEM\r\n\r\n");
+
+			// start listening for data and letting user know to send XMODEM data
+			if (xmodem_receive() == X_OK) {
+				comm_tx_str("\r\nflash updated; booting.\r\n\r\n");
+				break;
+			}
 
 			// if xmodem exits, there was a failure. repeat the process.
-			comm_tx_str((uint8_t*)"\r\nfailed to update. try again.\r\n");
+			comm_tx_str("\r\nfailed to update; try again.\r\n");
 		}
 	}
 
-	// bootloader is not activated; jump to user code
+	// bootloader is either done not activated; jump to user code
 	jump_to_user_app();
 }
 
diff --git a/bootloader_hk32f030m_uart_xmodem/code/src/usart.c b/bootloader_hk32f030m_uart_xmodem/code/src/usart.c
index 9d96e44..d47d0a3 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/src/usart.c
+++ b/bootloader_hk32f030m_uart_xmodem/code/src/usart.c
@@ -41,16 +41,14 @@ uint16_t rxlen = 0;
  */
 void comm_init()
 {
-	// USART_InitTypeDef usart;
-	// NVIC_InitTypeDef nvic;
-
 	// enable GPIO clock
-	RCC_AHBPeriphClockCmd(USART_TX_GPIO_CLK | USART_RX_GPIO_CLK, ENABLE);
+	// RCC_AHBPeriphClockCmd(USART_TX_GPIO_CLK | USART_RX_GPIO_CLK, ENABLE);
 
 	// configure USART GPIO
 	GPIO_PinAFConfig(USART_TX_PORT, USART_TX_PINSRC, GPIO_AF_1);
 	GPIO_PinAFConfig(USART_RX_PORT, USART_RX_PINSRC, GPIO_AF_1);
 
+	/* these have been configured in user_io.c to save space
 	USART_RX_PORT->MODER   &= ~(GPIO_MODER_MODER0     << 2 * USART_RX_PIN);
 	USART_RX_PORT->MODER   |=  (GPIO_Mode_AF          << 2 * USART_RX_PIN);	// alt function
 
@@ -58,46 +56,25 @@ void comm_init()
 	USART_TX_PORT->OTYPER  &= ~(GPIO_OTYPER_OT_0      <<     USART_TX_PIN);	// push pull
 	USART_TX_PORT->OSPEEDR &= ~(GPIO_OSPEEDR_OSPEEDR0 << 2 * USART_TX_PIN);	// slow
 	USART_TX_PORT->MODER   |=  (GPIO_Mode_AF          << 2 * USART_TX_PIN);	// alt function
-
-	// configure NVIC
-	/*
-	nvic.NVIC_IRQChannel = USART1_IRQn;
-	nvic.NVIC_IRQChannelPriority = 1;
-	nvic.NVIC_IRQChannelCmd = ENABLE;
-	NVIC_Init(&nvic);
 	*/
 
 	// enable USART clock
 	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
 
-	/*
-	// configure USART peripheral
-	usart.USART_BaudRate   = BAUDRATE;
-	usart.USART_WordLength = USART_WordLength_8b;
-	usart.USART_StopBits   = USART_StopBits_1;
-	usart.USART_Parity     = USART_Parity_No;
-	usart.USART_Mode       = USART_Mode_Rx | USART_Mode_Tx;
-	usart.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
-	USART_Init(USART1, &usart);
-	*/
-
 	// configure USART peripheral manually
-	// we do this as the library uses division which bloats flash space
+	// we do this as the library bloats flash space (division, verbose, ...)
 	USART1->CR1 = 0;								// disable USART
 	USART1->CR1 = USART_Mode_Rx | USART_Mode_Tx;	// 8 bits, no parity, tx/rx enabled
 	USART1->CR2 = 0;								// 1 stop bit
 	USART1->CR3 = 0;
 	USART1->BRR = 0x45;								// 115200 baud rate @8MHz (per datasheet)
 
-	// enable USART interrupts
-	// USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
-
 	// enable USART
 	USART1->CR1 |= USART_CR1_UE;
 }
 
 /**
- * @brief   Receives data from USART.
+ * @brief   Receives data from USART in a polling manner.
  * @param   *data: Array to save the received data.
  * @param   length:  Size of the data.
  * @return  status: Report about the success of the receiving.
@@ -107,24 +84,8 @@ BL_comm_status comm_rx(uint8_t *data, uint16_t length)
 	uint16_t i;
 	uint16_t timeout;
 
-	/*
-	// wait for more data to arrive
-	timeout = COMM_TIMEOUT;
-	while (rxlen < length) {
-		timeout--;
-		if (!timeout) return COMM_RX_TIMEOUT;
-	}
-
-	// copy data to final buffer
 	for (i = 0; i < length; i++) {
-		data[i] = rxbuf[rxptr++];
-		if (rxptr >= RX_BUF_LEN) rxptr = 0;
-		rxlen--;
-	}
-	*/
-
-	for (i = 0; i < length; i++) {
-		timeout = 0xffff;
+		timeout = COMM_TIMEOUT;
 		while (!(USART1->ISR & USART_ISR_RXNE_Msk) && timeout) {
 			timeout--;
 		}
@@ -160,40 +121,19 @@ BL_comm_status comm_tx_byte(uint8_t data)
  * @param   *data: String array.
  * @return  status: Report about the success of the transmission.
  */
-BL_comm_status comm_tx_str(uint8_t *data)
+BL_comm_status comm_tx_str(char *data)
 {
 	uint8_t  i;
 	uint16_t len = 0;
 
 	len = strlen((const char *)data);
 
-	for(i = 0; i < len; i++) {
+	for (i = 0; i < len; i++) {
 		comm_tx_byte(data[i]);
 	}
 
-	while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
+	while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
 
 	return COMM_OK;
 }
 
-/*
-void USART1_IRQHandler()
-{
-	uint8_t data;
-
-	if (USART1->ISR & USART_ISR_RXNE_Msk) {
-		// read data
-		data = USART1->RDR;
-
-		// only add data if there is room
-		if (rxlen >= RX_BUF_LEN) return;
-		rxlen++;
-
-		// next position
-		if (++rxptr >= RX_BUF_LEN) rxptr = 0;
-
-		// save data
-		rxbuf[rxptr] = data;
-	}
-}
-*/
diff --git a/bootloader_hk32f030m_uart_xmodem/code/src/user_io.c b/bootloader_hk32f030m_uart_xmodem/code/src/user_io.c
index c144808..d0f41f7 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/src/user_io.c
+++ b/bootloader_hk32f030m_uart_xmodem/code/src/user_io.c
@@ -14,8 +14,9 @@
 void user_io_init()
 {
 	// enable gpio clocks
-	RCC_AHBPeriphClockCmd(BTN_CLK | LED_CLK, ENABLE);
+	RCC_AHBPeriphClockCmd(BTN_CLK | LED_CLK | RCC_AHBPeriph_GPIOB, ENABLE);
 
+	/* --original method, not space efficient
 	// configure led
 #if LED_ACT_DIR == 0
 	LED_PORT->BSRR    = (1 << LED_PIN);								// idle high
@@ -25,16 +26,44 @@ void user_io_init()
 	LED_PORT->OTYPER  &= ~(GPIO_OTYPER_OT_0      <<     LED_PIN);	// push pull
 	LED_PORT->OSPEEDR &= ~(GPIO_OSPEEDR_OSPEEDR0 << 2 * LED_PIN);	// slow
 	LED_PORT->MODER   &= ~(GPIO_MODER_MODER0     << 2 * LED_PIN);
-	LED_PORT->MODER   |=  (GPIO_Mode_OUT         << 2 * LED_PIN);	// output
+	LED_PORT->MODER    =  (GPIO_Mode_OUT         << 2 * LED_PIN);	// output
 
 	// configure button
 	BTN_PORT->MODER   &= ~(GPIO_MODER_MODER0     << 2 * BTN_PIN);	// input
 	BTN_PORT->PUPDR   &= ~(GPIO_PUPDR_PUPDR0     << 2 * BTN_PIN);
 #if BTN_ACT_DIR == 0
-	BTN_PORT->PUPDR   |=  (GPIO_PuPd_UP          << 2 * BTN_PIN);	// pulled high
+	//BTN_PORT->PUPDR   |=  (GPIO_PuPd_UP          << 2 * BTN_PIN);	// pulled high
+	BTN_PORT->PUPDR    = (GPIO_PuPd_UP   << 2 * BTN_PIN);	// pulled high
 #else
-	BTN_PORT->PUPDR   |=  (GPIO_PuPd_DOWN        << 2 * BTN_PIN);	// pulled low
+	//BTN_PORT->PUPDR   |=  (GPIO_PuPd_DOWN        << 2 * BTN_PIN);	// pulled low
+	BTN_PORT->PUPDR    = (GPIO_PuPd_DOWN << 2 * BTN_PIN);	// pulled low
 #endif
+	*/
+
+	/* new method, configure USART pins at the same time as LED and btn
+	 * at they are on the same ports
+	 */
+
+	// default MODER for GPIOB and GPIOD are 0xFBFF
+	// pin 5 _must_ be configured as AF, otherwise you'll kill debugging!
+
+	// configure button as input
+	BTN_PORT->MODER    = 0x0;
+#if BTN_ACT_DIR == 0
+	//BTN_PORT->PUPDR   |=  (GPIO_PuPd_UP          << 2 * BTN_PIN);	// pulled high
+	BTN_PORT->PUPDR    = (GPIO_PuPd_UP   << 2 * BTN_PIN);	// pulled high
+#else
+	//BTN_PORT->PUPDR   |=  (GPIO_PuPd_DOWN        << 2 * BTN_PIN);	// pulled low
+	BTN_PORT->PUPDR    = (GPIO_PuPd_DOWN << 2 * BTN_PIN);	// pulled low
+#endif
+
+	// configure LED as PP output, USART TX as AF
+	LED_PORT->OTYPER   = 0;
+	LED_PORT->OSPEEDR  = 0;
+	LED_PORT->MODER    = 0x800 | (GPIO_Mode_OUT << (2 * LED_PIN)) | (GPIO_Mode_AF << (2 * 1));
+
+	// configure USART RX as AF
+	GPIOB->MODER	   = 0x800									  | (GPIO_Mode_AF << (2 * 4));
 }
 
 void user_led_init()
@@ -43,14 +72,3 @@ void user_led_init()
 	SysTick_Config(8000000 / 20);
 }
 
-void user_led_set(uint8_t lit)
-{
-#if LED_ACT_DIR == 0
-	if (lit) LED_PORT->BRR  = (1 << LED_PIN);
-	else     LED_PORT->BSRR = (1 << LED_PIN);
-#else
-	if (lit) LED_PORT->BSRR = (1 << LED_PIN);
-	else     LED_PORT->BRR  = (1 << LED_PIN);
-#endif
-}
-
diff --git a/bootloader_hk32f030m_uart_xmodem/code/src/xmodem.c b/bootloader_hk32f030m_uart_xmodem/code/src/xmodem.c
index b1af977..8c2143e 100644
--- a/bootloader_hk32f030m_uart_xmodem/code/src/xmodem.c
+++ b/bootloader_hk32f030m_uart_xmodem/code/src/xmodem.c
@@ -34,7 +34,7 @@ static BL_xmodem_status xmodem_error_handler(uint8_t *error_number, uint8_t max_
  * @param   void
  * @return  void
  */
-void xmodem_receive(void)
+BL_xmodem_status xmodem_receive(void)
 {
 	volatile BL_xmodem_status status = X_OK;
 	uint8_t error_number = 0u;
@@ -51,7 +51,7 @@ void xmodem_receive(void)
 		BL_comm_status status_c = comm_rx(&header, 1);
 
 		/* Spam the host (until we receive something) with ACSII "C", to notify it, we want to use CRC-16. */
-		if ((status_c != COMM_OK) && (x_first_packet_rcvd == false)) {
+		if ((status_c != COMM_OK) && (x_first_packet_rcvd == 0)) {
 			comm_tx_byte(X_C);
 		}
 
@@ -96,9 +96,7 @@ void xmodem_receive(void)
 			case X_EOT: {
 				/* ACK, feedback to user (as a text), then jump to user application. */
 				comm_tx_byte(X_ACK);
-				comm_tx_str((uint8_t*)"\r\nfirmware updated.\r\nstarting firmware.\r\n\r\n");
-				jump_to_user_app();
-				break;
+				return X_OK;
 			}
 
 			/* Abort from host. */
@@ -116,6 +114,8 @@ void xmodem_receive(void)
 			}
 		}
 	}
+
+	return status;
 }
 
 /**
@@ -127,22 +127,19 @@ void xmodem_receive(void)
 static uint16_t xmodem_calc_crc(uint8_t *data, uint16_t length)
 {
     uint16_t crc = 0u;
-    while (length)
-    {
+
+    while (length) {
         length--;
         crc = crc ^ ((uint16_t)*data++ << 8u);
-        for (uint8_t i = 0u; i < 8u; i++)
-        {
-            if (crc & 0x8000u)
-            {
+        for (uint8_t i = 0u; i < 8u; i++) {
+            if (crc & 0x8000u) {
                 crc = (crc << 1u) ^ 0x1021u;
-            }
-            else
-            {
+            } else {
                 crc = crc << 1u;
             }
         }
     }
+
     return crc;
 }
 
@@ -154,7 +151,8 @@ static uint16_t xmodem_calc_crc(uint8_t *data, uint16_t length)
 static BL_xmodem_status xmodem_handle_packet(uint8_t header)
 {
 	BL_xmodem_status status = X_OK;
-	uint16_t size = 0u;
+	uint16_t size = 0;
+	uint32_t i;
 
 	/* 2 bytes for packet number, 1024 for data, 2 for CRC*/
 	uint8_t rcvd_packet_number[X_PACKET_NUMBER_SIZE];
@@ -190,13 +188,9 @@ static BL_xmodem_status xmodem_handle_packet(uint8_t header)
 		status |= X_ERROR_UART;
 	}
 
-	/* If it is the first packet, then erase the memory. */
-	if ((status == X_OK) && (x_first_packet_rcvd == false)) {
-		if (flash_erase_user_app() == FLASH_OK) {
-			x_first_packet_rcvd = true;
-		} else {
-			status |= X_ERROR_FLASH;
-		}
+	/* If it is the first packet, then mark it. If you want to erase all flash, do it here. */
+	if ((status == X_OK)) { // && (x_first_packet_rcvd == 0)) {
+		x_first_packet_rcvd = 1;
 	}
 
 	/* Error handling and flashing. */
@@ -219,11 +213,22 @@ static BL_xmodem_status xmodem_handle_packet(uint8_t header)
 	}
 
 	/* Do the actual flashing if there weren't any errors. */
-	if ((status == X_OK) &&
-			(flash_write(xmodem_flash_w_addr, rcvd_packet_data, size)) != FLASH_OK) {
+	if (status == X_OK) {
+		/* first, erase pages depending on size */
+		for (i = 0; i < size; i += FLASH_ERASE_PAGE_SIZE) {
+			if (flash_erase_page(xmodem_flash_w_addr + i) != FLASH_OK) {
+				/* Flashing error. */
+				status |= X_ERROR_FLASH;
+			}
+		}
 
-		/* Flashing error. */
-		status |= X_ERROR_FLASH;
+		/* then write data to these cleared pages */
+		if (status == X_OK) {
+			if (flash_write(xmodem_flash_w_addr, rcvd_packet_data, size) != FLASH_OK) {
+				/* Flashing error. */
+				status |= X_ERROR_FLASH;
+			}
+		}
 	}
 
 	/* Raise the packet number and the address counters (if there weren't any errors). */
diff --git a/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/startup_hk32f030mf4p6.s b/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/startup_hk32f030mf4p6.s
index ed9f0ab..9e2eaea 100644
--- a/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/startup_hk32f030mf4p6.s
+++ b/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/startup_hk32f030mf4p6.s
@@ -112,8 +112,8 @@ Infinite_Loop:
 g_pfnVectors:
   .word  _estack
   .word  Reset_Handler
-  .word  NMI_Handler
-  .word  HardFault_Handler
+  .word  Default_Handler			// NMI_Handler
+  .word  Default_Handler			// HardFault_Handler
   .word  0
   .word  0
   .word  0
@@ -121,43 +121,43 @@ g_pfnVectors:
   .word  0
   .word  0
   .word  0
-  .word  SVC_Handler
+  .word  Default_Handler			// SVC_Handler
   .word  0
   .word  0
-  .word  PendSV_Handler
+  .word  Default_Handler			// PendSV_Handler
   .word  SysTick_Handler  
-  .word  WWDG_IRQHandler                   /* Window WatchDog              */
-  .word  0                                 /* Reserved                     */
-  .word  EXTI11_IRQHandler                 /* EXTI Line 11 interrupt(AWU_WKP) */
-  .word  FLASH_IRQHandler                  /* FLASH                        */
-  .word  RCC_IRQHandler                    /* RCC                          */
-  .word  EXTI0_IRQHandler                  /* EXTI Line 0                  */
-  .word  EXTI1_IRQHandler                  /* EXTI Line 1                  */
-  .word  EXTI2_IRQHandler                  /* EXTI Line 2                  */
-  .word  EXTI3_IRQHandler                  /* EXTI Line 3                  */
-  .word  EXTI4_IRQHandler                  /* EXTI Line 4                  */
-  .word  EXTI5_IRQHandler                  /* EXTI Line 5                  */
-  .word  TIM1_BRK_IRQHandler               /* TIM1 break interrupt         */
-  .word  ADC1_IRQHandler                   /* ADC1 interrupt, combined with EXTI line 8 */
-  .word  TIM1_UP_TRG_COM_IRQHandler        /* TIM1 Update, Trigger and Commutation */
-  .word  TIM1_CC_IRQHandler                /* TIM1 Capture Compare         */
-  .word  TIM2_IRQHandler                   /* TIM2                         */
-  .word  0                                 /* Reserved                     */
-  .word  TIM6_IRQHandler                   /* TIM6                         */
-  .word  0                                 /* Reserved                     */
-  .word  0                                 /* Reserved                     */
-  .word  0                                 /* Reserved                     */
-  .word  EXTI6_IRQHandler                  /* EXTI Line 6                  */
-  .word  EXTI7_IRQHandler                  /* EXTI Line 7                  */
-  .word  I2C1_IRQHandler                   /* I2C1 global interrupt, combined with EXTI Line 10 */
-  .word  0                                 /* Reserved                     */
-  .word  SPI1_IRQHandler                   /* SPI1                         */
-  .word  0                                 /* Reserved                     */
-  .word  USART1_IRQHandler                 /* USART1 global interrupt, combined with EXTI Line 9 */
-  .word  0                                 /* Reserved                     */
-  .word  0                                 /* Reserved                     */
-  .word  0                                 /* Reserved                     */
-  .word  0                                 /* Reserved                     */
+//  .word  WWDG_IRQHandler                   /* Window WatchDog              */
+//  .word  0                                 /* Reserved                     */
+//  .word  EXTI11_IRQHandler                 /* EXTI Line 11 interrupt(AWU_WKP) */
+//  .word  FLASH_IRQHandler                  /* FLASH                        */
+//  .word  RCC_IRQHandler                    /* RCC                          */
+//  .word  EXTI0_IRQHandler                  /* EXTI Line 0                  */
+//  .word  EXTI1_IRQHandler                  /* EXTI Line 1                  */
+//  .word  EXTI2_IRQHandler                  /* EXTI Line 2                  */
+//  .word  EXTI3_IRQHandler                  /* EXTI Line 3                  */
+//  .word  EXTI4_IRQHandler                  /* EXTI Line 4                  */
+//  .word  EXTI5_IRQHandler                  /* EXTI Line 5                  */
+//  .word  TIM1_BRK_IRQHandler               /* TIM1 break interrupt         */
+//  .word  ADC1_IRQHandler                   /* ADC1 interrupt, combined with EXTI line 8 */
+//  .word  TIM1_UP_TRG_COM_IRQHandler        /* TIM1 Update, Trigger and Commutation */
+//  .word  TIM1_CC_IRQHandler                /* TIM1 Capture Compare         */
+//  .word  TIM2_IRQHandler                   /* TIM2                         */
+//  .word  0                                 /* Reserved                     */
+//  .word  TIM6_IRQHandler                   /* TIM6                         */
+//  .word  0                                 /* Reserved                     */
+//  .word  0                                 /* Reserved                     */
+//  .word  0                                 /* Reserved                     */
+//  .word  EXTI6_IRQHandler                  /* EXTI Line 6                  */
+//  .word  EXTI7_IRQHandler                  /* EXTI Line 7                  */
+//  .word  I2C1_IRQHandler                   /* I2C1 global interrupt, combined with EXTI Line 10 */
+//  .word  0                                 /* Reserved                     */
+//  .word  SPI1_IRQHandler                   /* SPI1                         */
+//  .word  0                                 /* Reserved                     */
+//  .word  USART1_IRQHandler                 /* USART1 global interrupt, combined with EXTI Line 9 */
+//  .word  0                                 /* Reserved                     */
+//  .word  0                                 /* Reserved                     */
+//  .word  0                                 /* Reserved                     */
+//  .word  0                                 /* Reserved                     */
 
 /*******************************************************************************
 *
@@ -182,6 +182,7 @@ g_pfnVectors:
   .weak      SysTick_Handler
   .thumb_set SysTick_Handler,Default_Handler
 
+/*
   .weak      WWDG_IRQHandler
   .thumb_set WWDG_IRQHandler,Default_Handler
 
@@ -244,3 +245,4 @@ g_pfnVectors:
 
   .weak      USART1_IRQHandler
   .thumb_set USART1_IRQHandler,Default_Handler
+*/
diff --git a/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/system_hk32f030m.c b/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/system_hk32f030m.c
index 11bdcba..587273c 100644
--- a/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/system_hk32f030m.c
+++ b/bootloader_hk32f030m_uart_xmodem/driver/CMSIS/HK32F030M/Source/system_hk32f030m.c
@@ -170,7 +170,7 @@ static void SetSysClockToHSI(void)
      * Datasheet and RM was updated in 2023 which derated flash programming from 4MHz
      * 0x07 = 4MHz, 0x08 = 2MHz. change as you see fit */
 	RCC->CFGR4 &= ~(RCC_RCC_CFGR4_FLITFCLK_PRE | RCC_RCC_CFGR4_FLITFCLK_SE);
-	RCC->CFGR4 |= (((uint32_t)0x07) << RCC_RCC_CFGR4_FLITFCLK_PRE_Pos);
+	RCC->CFGR4 |= (((uint32_t)0x08) << RCC_RCC_CFGR4_FLITFCLK_PRE_Pos);
 
 	/* Wait until HSI is ready; if timeout is reached, then exit */
 	do {
@@ -386,33 +386,30 @@ static void SetSysClockToEXTCLK(void)
   */
 void SystemCoreClockUpdate (void)
 {
-  uint32_t tmp = 0, presc = 0;
+	uint32_t tmp = 0, presc = 0;
 
-  /* Get SYSCLK source -------------------------------------------------------*/
-  tmp = RCC->CFGR & RCC_CFGR_SWS;
+	/* Get SYSCLK source -------------------------------------------------------*/
+	tmp = RCC->CFGR & RCC_CFGR_SWS;
 
-  switch (tmp)
-  {
-    case RCC_CFGR_SWS_HSI:  /* HSI used as system clock */
-      SystemCoreClock = HCLK_FREQ;
-      break;
-	case RCC_CFGR_SWS_EXTCLK:	/* EXTCLK used as system clock */
-	  SystemCoreClock = EXTCLK_VALUE;
-	  break;
-	case RCC_CFGR_SWS_LSI:	/* LSI used as system clock */
-	  SystemCoreClock = LSI_VALUE;
-	  break;
+	switch (tmp) {
+		case RCC_CFGR_SWS_EXTCLK:		// EXTCLK used as system clock
+			SystemCoreClock = EXTCLK_VALUE;
+			break;
+		case RCC_CFGR_SWS_LSI:			// LSI used as system clock
+			SystemCoreClock = LSI_VALUE;
+			break;
 
-    default: /* HSI used as system clock */
-      SystemCoreClock = HCLK_FREQ;
-      break;
-  }
+		case RCC_CFGR_SWS_HSI:			// HSI used as system clock
+		default:
+			SystemCoreClock = HCLK_FREQ;
+			break;
+	}
   
-  /* Compute HCLK clock frequency ----------------*/
-  /* Get HCLK prescaler */
-  tmp = RCC->CFGR & RCC_CFGR_HPRE;
-  tmp = tmp >> 4;
-  presc = AHBPrescTable[tmp]; 
-  /* HCLK clock frequency */
-  SystemCoreClock = SystemCoreClock/presc;
+	/* Compute HCLK clock frequency ----------------*/
+	/* Get HCLK prescaler */
+	tmp = RCC->CFGR & RCC_CFGR_HPRE;
+	tmp = tmp >> 4;
+	presc = AHBPrescTable[tmp];
+	/* HCLK clock frequency */
+	SystemCoreClock = SystemCoreClock/presc;
 }