Flow control

The RTS and CTS device pins provide RTS and/or CTS  flow control. CTS flow control signals the host to stop sending serial data to the device. RTS flow control lets the host signal the device so it will not send the data in the serial transmit buffer out the UART. The following diagram shows the internal data flow, with the five most common pin signals.

The firmware has Hardware flow control (CTS) configured by default. You must configure CTS flow control on the host side for it to work.

You must configure Software flow control (XON) on both the host and device side for it to work.

If you change the CS command from 0, then CTS flow control will not work even if you have it configured on the host.