rtt-stdio新建工程编译后提示串口出错请问要怎么修改

../drivers/drv_usart.c:338:16: error: 'struct serial_configure' has no member named 'flowcontrol'
switch (cfg->flowcontrol)
^
../drivers/drv_usart.c:340:10: error: 'RT_SERIAL_FLOWCONTROL_NONE' undeclared (first use in this function)
case RT_SERIAL_FLOWCONTROL_NONE:
^
../drivers/drv_usart.c:340:10: note: each undeclared identifier is reported only once for each function it appears in
../drivers/drv_usart.c:343:10: error: 'RT_SERIAL_FLOWCONTROL_CTSRTS' undeclared (first use in this function)
case RT_SERIAL_FLOWCONTROL_CTSRTS:
^
arm-none-eabi-gcc "../applications/main.c"
make: *** [drivers/subdir.mk:99: drivers/drv_usart.o] Error 1
make: *** Waiting for unfinished jobs....
"make -j8 all" terminated with exit code 2. Build might be incomplete.