Fix struct usart member mistake. Add example-usart.

example-usart/Makefile

@@ -0,0 +1,47 @@
+# Makefile for example application of Chopstx
+
+PROJECT = sample
+
+### Currently, it is for STM32 Nucleo L432
+### 
+### Please change lines started with '###' for Cortex-M3 board.
+###
+### Please change lines started with '###' for Cortex-M0+ board
+### (STM32F0 Discovery).
+
+CHOPSTX = ..
+LDSCRIPT= sample.ld.m4
+### LDSCRIPT= sample.ld
+### LDSCRIPT= sample.ld.m3
+CSRC = sample.c
+
+CHIP=stm32l4
+USE_SYS = yes
+USE_USART = yes
+
+###################################
+CROSS = arm-none-eabi-
+CC   = $(CROSS)gcc
+LD   = $(CROSS)gcc
+OBJCOPY   = $(CROSS)objcopy
+
+### MCU   = cortex-m3
+### MCU   = cortex-m0
+MCU   = cortex-m4
+CWARN = -Wall -Wextra -Wstrict-prototypes
+DEFS  = -DUSE_SYS3 -DFREE_STANDING -DMHZ=80
+### DEFS  = -DFREE_STANDING -DUSE_SYS3 -DBUSY_LOOP -DCHX_FLAGS_MAIN=CHOPSTX_SCHED_RR
+OPT   = -O3 -Os -g
+LIBS  =
+
+####################
+include ../rules.mk
+
+board.h:
+	@echo Please make a symbolic link \'board.h\' to a file in ../board;
+	@exit 1
+
+sys.c: board.h
+
+distclean: clean
+	rm -f board.h