uart hardware flow control problem of nrf52_pca10040 #uart #nrf52832


Hi guys,
     I met a problem here and hop anyone can help. Thanks.

     I enable hardware control in menuconfig, build a firmware of hci_uart sample and burn the firmware into nrf52_pca10040 (nrf52832), 
(top menu) → Device Drivers → Serial Drivers → nRF UART nrfx drivers
                                                                     Zephyr Kernel Configuration
[*] UART Port 0 Driver type (nRF UART 0)  --->
[*] Enable interrupt support on port 0
[ ] Enable parity bit
[*] Enable flow control
and then connect it  with my NXP board via uart, tx rx rts cts,
but when I attach the ble with command hciattach, it prints time out and seems the uart cannot communicate.
root~# hciattach /dev/ttymxc2 any 115200
Device setup complete
root:~# Bluetooth: hci0 command 0x1003 tx timeout
root:~# Bluetooth: hci0 command 0x1001 tx timeout
root:~# Bluetooth: hci0 command 0x1009 tx timeout
So I wonder if the hardware flow control works fine with nrf52832 or zephyr ? Or maybe my way to enable hardware flow control is wrong ?

By the way, is there any problems that we use software flow control instead of hardware flow control when  the baudrate of uart is 1M ?

Thanks if someone can give me any advice.