diff --git a/myapps/practice/00-uart-tx/Makefile b/myapps/practice/00-uart-tx/Makefile
new file mode 100644
index 0000000..f99b21f
--- /dev/null
+++ b/myapps/practice/00-uart-tx/Makefile
@@ -0,0 +1,166 @@
+######################################
+# target
+######################################
+TARGET = ch592_blinky
+# ../../
+
+
+######################################
+# building variables
+######################################
+# debug build?
+DEBUG = 1
+# optimization for size
+OPT = -Os
+
+
+#######################################
+# paths
+#######################################
+# Build path
+BUILD_DIR = build
+
+######################################
+# source
+######################################
+# C sources
+C_SOURCES = \
+src/main.c \
+../../../vendor/StdPeriphDriver/CH59x_clk.c \
+../../../vendor/StdPeriphDriver/CH59x_gpio.c \
+../../../vendor/StdPeriphDriver/CH59x_pwr.c \
+../../../vendor/StdPeriphDriver/CH59x_sys.c \
+../../../vendor/StdPeriphDriver/CH59x_uart3.c \
+../../../vendor/RVMSIS/core_riscv.c \
+
+
+# ASM sources
+ASM_SOURCES =  \
+../../../vendor/Startup/startup_CH592.S
+
+#######################################
+# binaries
+#######################################
+#PREFIX = riscv-none-elf-
+#PREFIX = riscv64-elf-
+#debian
+#PREFIX = riscv64-unknown-elf-
+PREFIX = riscv-wch-elf-
+
+CC = $(PREFIX)gcc
+AS = $(PREFIX)gcc -x assembler-with-cpp
+CP = $(PREFIX)objcopy
+SZ = $(PREFIX)size
+
+HEX = $(CP) -O ihex
+BIN = $(CP) -O binary -S
+
+#######################################
+# CFLAGS
+#######################################
+# cpu
+CPU = -march=rv32imac_zicsr -mabi=ilp32 -msmall-data-limit=8 
+
+# For gcc version less than v12
+# CPU = -march=rv32imac -mabi=ilp32 -msmall-data-limit=8
+
+# fpu
+FPU = 
+
+# float-abi
+FLOAT-ABI =
+
+# mcu
+MCU = $(CPU) $(FPU) $(FLOAT-ABI)
+
+# AS includes
+AS_INCLUDES = 
+
+# C includes
+C_INCLUDES =  \
+-I../../../vendor/StdPeriphDriver/inc \
+-I../../../vendor/RVMSIS \
+-I../../../vendor/Core \
+-Isrc/include
+
+# compile gcc flags
+ASFLAGS = $(MCU) $(AS_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections
+
+CFLAGS = $(MCU) $(C_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections
+
+ifeq ($(DEBUG), 1)
+CFLAGS += -g -gdwarf-2
+endif
+
+
+# Generate dependency information
+CFLAGS += -MMD -MP -MF"$(@:%.o=%.d)"
+
+
+#######################################
+# LDFLAGS
+#######################################
+# link script
+LDSCRIPT = ../../../vendor/Ld/Link.ld 
+
+# libraries
+LIBS = -lc -lm -lnosys ../../../vendor/StdPeriphDriver/libISP592.a
+LIBDIR = 
+LDFLAGS = $(MCU) -mno-save-restore -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wunused -Wuninitialized -T $(LDSCRIPT) -nostartfiles -Xlinker --gc-sections -Wl,-Map=$(BUILD_DIR)/$(TARGET).map --specs=nano.specs $(LIBS)
+
+# default action: build all
+all: $(BUILD_DIR)/$(TARGET).elf $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin
+
+
+#######################################
+# build the application
+#######################################
+# list of objects
+OBJECTS = $(addprefix $(BUILD_DIR)/,$(notdir $(C_SOURCES:.c=.o)))
+vpath %.c $(sort $(dir $(C_SOURCES)))
+
+# list of ASM program objects
+OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASM_SOURCES:.S=.o)))
+vpath %.S $(sort $(dir $(ASM_SOURCES)))
+
+$(BUILD_DIR)/%.o: %.c Makefile | $(BUILD_DIR)
+	$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $@
+
+$(BUILD_DIR)/%.o: %.S Makefile | $(BUILD_DIR)
+	$(AS) -c $(CFLAGS) $< -o $@
+#$(LUAOBJECTS) $(OBJECTS)
+$(BUILD_DIR)/$(TARGET).elf: $(OBJECTS) Makefile
+	$(CC) $(OBJECTS) $(LDFLAGS) -o $@
+	$(SZ) $@
+
+$(BUILD_DIR)/%.hex: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
+	$(HEX) $< $@
+	
+$(BUILD_DIR)/%.bin: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
+	$(BIN) $< $@	
+	
+$(BUILD_DIR):
+	mkdir $@		
+
+#######################################
+# Program
+#######################################
+
+isp: $(BUILD_DIR)/$(TARGET).bin
+	wchisp flash $(BUILD_DIR)/$(TARGET).bin
+
+flash: $(BUILD_DIR)/$(TARGET).bin
+	wlink flash $(BUILD_DIR)/$(TARGET).bin
+
+#######################################
+# clean up
+#######################################
+clean:
+	-rm -fR $(BUILD_DIR)
+  
+#######################################
+# dependencies
+#######################################
+-include $(wildcard $(BUILD_DIR)/*.d)
+
+# *** EOF ***
diff --git a/myapps/practice/00-uart-tx/src/main.c b/myapps/practice/00-uart-tx/src/main.c
new file mode 100644
index 0000000..1488237
--- /dev/null
+++ b/myapps/practice/00-uart-tx/src/main.c
@@ -0,0 +1,21 @@
+// RXD3/TXD3: PA4/PA5
+
+
+#include "CH59x_common.h"
+#include <string.h>
+
+
+int main()
+{
+  char *s = "Hello world\r\n";
+  SetSysClock(CLK_SOURCE_PLL_60MHz);
+  
+  GPIOA_ModeCfg(GPIO_Pin_5, GPIO_ModeOut_PP_5mA);
+  UART3_DefInit();  
+  
+  while (1) {
+    UART3_SendString((uint8_t *)s, strlen(s));
+    mDelaymS(1000);
+  }
+  
+}
diff --git a/myapps/practice/00a-uart-rx/Makefile b/myapps/practice/00a-uart-rx/Makefile
new file mode 100644
index 0000000..f99b21f
--- /dev/null
+++ b/myapps/practice/00a-uart-rx/Makefile
@@ -0,0 +1,166 @@
+######################################
+# target
+######################################
+TARGET = ch592_blinky
+# ../../
+
+
+######################################
+# building variables
+######################################
+# debug build?
+DEBUG = 1
+# optimization for size
+OPT = -Os
+
+
+#######################################
+# paths
+#######################################
+# Build path
+BUILD_DIR = build
+
+######################################
+# source
+######################################
+# C sources
+C_SOURCES = \
+src/main.c \
+../../../vendor/StdPeriphDriver/CH59x_clk.c \
+../../../vendor/StdPeriphDriver/CH59x_gpio.c \
+../../../vendor/StdPeriphDriver/CH59x_pwr.c \
+../../../vendor/StdPeriphDriver/CH59x_sys.c \
+../../../vendor/StdPeriphDriver/CH59x_uart3.c \
+../../../vendor/RVMSIS/core_riscv.c \
+
+
+# ASM sources
+ASM_SOURCES =  \
+../../../vendor/Startup/startup_CH592.S
+
+#######################################
+# binaries
+#######################################
+#PREFIX = riscv-none-elf-
+#PREFIX = riscv64-elf-
+#debian
+#PREFIX = riscv64-unknown-elf-
+PREFIX = riscv-wch-elf-
+
+CC = $(PREFIX)gcc
+AS = $(PREFIX)gcc -x assembler-with-cpp
+CP = $(PREFIX)objcopy
+SZ = $(PREFIX)size
+
+HEX = $(CP) -O ihex
+BIN = $(CP) -O binary -S
+
+#######################################
+# CFLAGS
+#######################################
+# cpu
+CPU = -march=rv32imac_zicsr -mabi=ilp32 -msmall-data-limit=8 
+
+# For gcc version less than v12
+# CPU = -march=rv32imac -mabi=ilp32 -msmall-data-limit=8
+
+# fpu
+FPU = 
+
+# float-abi
+FLOAT-ABI =
+
+# mcu
+MCU = $(CPU) $(FPU) $(FLOAT-ABI)
+
+# AS includes
+AS_INCLUDES = 
+
+# C includes
+C_INCLUDES =  \
+-I../../../vendor/StdPeriphDriver/inc \
+-I../../../vendor/RVMSIS \
+-I../../../vendor/Core \
+-Isrc/include
+
+# compile gcc flags
+ASFLAGS = $(MCU) $(AS_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections
+
+CFLAGS = $(MCU) $(C_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections
+
+ifeq ($(DEBUG), 1)
+CFLAGS += -g -gdwarf-2
+endif
+
+
+# Generate dependency information
+CFLAGS += -MMD -MP -MF"$(@:%.o=%.d)"
+
+
+#######################################
+# LDFLAGS
+#######################################
+# link script
+LDSCRIPT = ../../../vendor/Ld/Link.ld 
+
+# libraries
+LIBS = -lc -lm -lnosys ../../../vendor/StdPeriphDriver/libISP592.a
+LIBDIR = 
+LDFLAGS = $(MCU) -mno-save-restore -fmessage-length=0 -fsigned-char -ffunction-sections -fdata-sections -Wunused -Wuninitialized -T $(LDSCRIPT) -nostartfiles -Xlinker --gc-sections -Wl,-Map=$(BUILD_DIR)/$(TARGET).map --specs=nano.specs $(LIBS)
+
+# default action: build all
+all: $(BUILD_DIR)/$(TARGET).elf $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).bin
+
+
+#######################################
+# build the application
+#######################################
+# list of objects
+OBJECTS = $(addprefix $(BUILD_DIR)/,$(notdir $(C_SOURCES:.c=.o)))
+vpath %.c $(sort $(dir $(C_SOURCES)))
+
+# list of ASM program objects
+OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASM_SOURCES:.S=.o)))
+vpath %.S $(sort $(dir $(ASM_SOURCES)))
+
+$(BUILD_DIR)/%.o: %.c Makefile | $(BUILD_DIR)
+	$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $@
+
+$(BUILD_DIR)/%.o: %.S Makefile | $(BUILD_DIR)
+	$(AS) -c $(CFLAGS) $< -o $@
+#$(LUAOBJECTS) $(OBJECTS)
+$(BUILD_DIR)/$(TARGET).elf: $(OBJECTS) Makefile
+	$(CC) $(OBJECTS) $(LDFLAGS) -o $@
+	$(SZ) $@
+
+$(BUILD_DIR)/%.hex: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
+	$(HEX) $< $@
+	
+$(BUILD_DIR)/%.bin: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
+	$(BIN) $< $@	
+	
+$(BUILD_DIR):
+	mkdir $@		
+
+#######################################
+# Program
+#######################################
+
+isp: $(BUILD_DIR)/$(TARGET).bin
+	wchisp flash $(BUILD_DIR)/$(TARGET).bin
+
+flash: $(BUILD_DIR)/$(TARGET).bin
+	wlink flash $(BUILD_DIR)/$(TARGET).bin
+
+#######################################
+# clean up
+#######################################
+clean:
+	-rm -fR $(BUILD_DIR)
+  
+#######################################
+# dependencies
+#######################################
+-include $(wildcard $(BUILD_DIR)/*.d)
+
+# *** EOF ***
diff --git a/myapps/practice/00a-uart-rx/src/main.c b/myapps/practice/00a-uart-rx/src/main.c
new file mode 100644
index 0000000..ef69f87
--- /dev/null
+++ b/myapps/practice/00a-uart-rx/src/main.c
@@ -0,0 +1,45 @@
+// RXD3/TXD3: PA4/PA5
+
+
+#include "CH59x_common.h"
+#include <stdbool.h>
+#include <string.h>
+
+char b[25];
+bool isrx = 0;
+
+__INTERRUPT
+__HIGH_CODE
+void UART3_IRQHandler()
+{
+  GPIOA_InverseBits(GPIO_Pin_8);
+  UART3_RecvString((uint8_t *)b);
+  //UART3_SendString((uint8_t *)b, strlen(b));
+  isrx = 1;
+}
+
+int main()
+{
+  //char *s = "Hello world\r\n";
+  SetSysClock(CLK_SOURCE_PLL_60MHz);
+  
+  GPIOA_SetBits(GPIO_Pin_8);  // LED
+  GPIOA_ModeCfg(GPIO_Pin_8, GPIO_ModeOut_PP_5mA);
+  
+  GPIOA_ModeCfg(GPIO_Pin_4, GPIO_ModeIN_PU);      // RXD3
+  GPIOA_ModeCfg(GPIO_Pin_5, GPIO_ModeOut_PP_5mA); // TXD3
+  
+  UART3_DefInit();
+  UART3_INTCfg(ENABLE, RB_IER_RECV_RDY);
+  PFIC_EnableIRQ(UART3_IRQn);
+  
+  while (1) {
+    
+    if (isrx == 1) {
+      UART3_SendString((uint8_t *)b, strlen(b));
+      isrx = 0;
+    }
+    mDelaymS(100);
+  }
+  
+}