Entering AT mode, XBee transmits 0XE0


I used XBee series 1, Firmware 10ec, Function set XBEE 802.15.4.

The setup is the following:

One XBee on a system I currently develop for
Another XBee connected to X-CTU to debug
When the system starts, it checks whether it’s XBee is set to 9600 bauds or 57600 bauds. To do so, 1st the serial port is set at 9600 and +++ is sent. If Ok is not received, then the serial port is set to 57600. Another +++ is sent, I get Ok and then send ATCN.

What bugs me is that on the other end, the XBee connected to X_CTU receives E0 E0 E0 E0 E0 E0 E0 E0 E0 (9 x E0) for each of the +++ and the ATCN command. These E0 will have the other party when connected fouled.

Why does the XBee transmists E0s when entering and leaving AT mode ? Is there a setting I am missing ?


Gilles Plante

Sounds more like you are holding the CONFIG line low or the DI line is being held low as the radio will not transmit a 0xE0 value unless you provide it that.

Hi mvut,

I kind of agree that one does not expect the XBee to transmit something by itself, but that’s the reality, for example when using API mode and you get a acknowledge !

But back to my issue.

Test no 1

XBee 1, which is a peripheral is set to transparent mode (AP=0), 64-bit addressing mode (DH not 0).

XBee 2, which plays the role of the remote command connected to XCTU is also in transparent mode.

Each time XBee 1 receives ‘+++’ or ‘ATCN’ on the serial port, XBee 2 receives 9 times E0.

Test no 2

XBee 1 is set as before.

XBee is set to API mode (AP=2).

Each time XBee 1 receives ‘+++’ or ‘ATCN’ on the serial port, XBee 2 receives an API frame of type RX packet 64-bit address… and guess what it gets as the data, E0 E0 E0 E0 E0 E0 E0 E0 E0 !

I don’t know what the CONFIG line is. If you are talking about the *RESET line, it’s not connected. Regarding the DI line, it’s connected to the micro-controller, it’s not specifically held low.

If I would hold the *RESET line low, it would not be able to get into AT mode, but I can.

Note that when using transparent mode, but with 16-bit address mode, I don’t get these E0s. The remote command will be in API mode, so it will get a single frame, easier to manage than a series of E0 in transparent mode, but I would like to know why XBee 1 sends this string of E0s, and how to prevent that. I can’t find this feature documented anywhere.

Does someone know ?