software flow control on xbee 2

Question

i need software flow control in my program, so i tried something with xctu. I created a packet (7E 00 04 08 01 00 7D 33 E3) and sent it to the module, but it respond back with "invalid command". where's the error? does the xbee 2 really support software flow control?

Answer 1

To answer the question, XBee S2 does not support software flow control. https://www.digi.com/support/forum/41701/does-xbee-s2-module-support-software-flow-control

The reason you get "invalid command" is that the AT command frame is not formed correctly.

7E - Delimiter
00 04 - Length
08 - Frame type (AT Command)
01 - Frame ID
00 7D - AT command (not a valid command!)
33 - Parameter
E3 - Checksum

You can see a complete example here: https://www.digi.com/resources/documentation/digidocs/90001539/#reference/r_frame_0x08.htm

Comments

thank you for your reply.  regarding the support of software flow control, why is this mode mentioned in the specs document then? http://www.science.smith.edu/~jcardell/Courses/EGR328/Readings/XBeeCookbook.pdf

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That document pertains to the XBee Series 1 radio (see the title: "XBee Cookbook Issue 1.4 for Series 1 (Freescale) with 802.15.4 Firmware"). Your question is about the Series 2 radio. All XBees do not share all of the same features.

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You are right, but is documented in the digi xbee 2 specs document as well.
Speaking about the frame i posted, i thought i need "7D" as the escape for Xon/Xoff. Is there a way to create the correct frame?

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What specs are you referring to? Software flow control is not mentioned anywhere in the XBee S2/S2B user guide: https://www.digi.com/resources/documentation/digidocs/pdfs/90000976.pdf

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apparently i've always looked at the wrong specs doc (http://www.farnell.com/datasheets/27606.pdf). so the only way to control the flow of the communication is via hardware, am i right?

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You are right. Also FYI, the PDF you have linked does not document software flow control as being supported by the product. If you are looking at page 60, where escape characters such as XON and XOFF are mentioned, the reason those are called out is that when API mode 2 is used, those characters (as well as 0x7E and 0x7D) are escaped to avoid interfering with any host processing that might misinterpret those bytes. I believe there may be SOME models of XBee that support software flow control, but XBee S2 is not one of them.