Flow control is a hardware configuration option that can be changed only in manufacturing mode. Manufacturing mode is be entered using AT+CFUN=5.
Flow control and other UART related options can be configure using the AT+SQNHWCFG command. The complete current hardware configuration can be shown using AT+SQNHWCFG?.
In the following example UART1 is configured to operate with “rtscts” flow control enabled:
AT+SQNHWCFG="uart1","enable","rtscts","921600","8","none","1","dcp"
Please refer to the Manufacturing Commands section of the AT Commands Reference Manual for more details on this command.