explain Xbee RTS ad CTS lines

Wireless & IoT
1

Can someone explain the operation of the RTS and CTS pins on the Xbee (Series 1, but I imagine both are the same) units?

I’m having a hard time understanding how thye are used. Are they outputs or inputs? Some folks say RTS is “ready to send” others say “request to send” - those have completely different meanings in my mind.

Also, if the RTS pin twiddles on one end of an Xbee connection, does the CTS pin twiddle on the other end of the connection?

Thanks

2

Check http://en.wikipedia.org/wiki/Flow_control

Then look in the 90000982_B.pdf doc on the series 1 XBees, Chapter 2, page 10 for the connection diagram and Page 12 describes the Flow control using RTS & CTS.

~CTS is Clear To Send. An output from the device receiving data from another device. When asserted (low) it is telling the other device it is Clear to send data.

~RTS is Request To Send. An input to the device sending the serial data meaning the other device is ready to receive data when asserted (low). The receiving device Request data.

When connecting two serial devices, say an XBee and a processor (UART) this is really connecting two UARTs together. TX (DO) on one device connects to the RX (DI) on the other device. Same with ~RTS & ~CTS. This way the definitions are uniform when looking from either device.

Any help?

3

gallamine:
Can someone explain the operation of the RTS and CTS pins on the Xbee (Series 1, but I imagine both are the same) units?

I’m having a hard time understanding how thye are used. Are they outputs or inputs? Some folks say RTS is “ready to send” others say “request to send” - those have completely different meanings in my mind.

Also, if the RTS pin twiddles on one end of an Xbee connection, does the CTS pin twiddle on the other end of the connection?

Thanks

As suggested - read the standard.

RTS = Request to Send.

Asserted then node A waits for clear to send (CTS) asserted by node B.

Node B will de-assert CTS whenever it wishes, to effect hardware flow control. When de-asserted, node A should cease sending within a byte-time or two.

Node A would be the data terminal equipment (DTE).

Node B would be the data communications equipment (DCE).

Way back, DCE was a modem and DTE was a data terminal or other data processor. In DB25 and DB9 connectors, the gender of the connector is given by the standard, for DTE and DCE.

Also in this EIA RS-232 standard are DCD, DSR, DTR, RI and other signals.