xbee sx dev kit transparent mode test

we have loaded the default settings on the 2 boards with the sx pro included in the kit, and trying the basics.

set the (SH, SL) of the SXpro #1 to match the (DH, DL) of the SXpro #2, and viceversa.
The board #1 is connected to the laptop through USB.
The board #2 is battery powered and with the DOUT (pin 3) of the DEVTEST pinheader connected to the DIN(pin 4);this to loopback/echo the original request back as response.

However, when opening the XCTU serial console and connecting to the board #1, nothing is being returned by board #2 as response to random keystrokes entered

the 2 dev boards included in the kit with the soldered sx pro dont have a loopback header.

when we try on the 3rd board with the xbee sx to close the loopback it works perfectly.

I guess then the question would be how to loopback on the XBP9XR board, since connecting DOUT to DIN doesnt work

could you please advice?

Re you sure you connected DI to DO? Form the sounds of it, you may have been off on the pins. DO and DI are pins 3 and 4 on this product.

I confirm the setup is correct, and that the behavior can be replicated. With the above configuration we observe the following:
the data is properly received by the SXPRO and the signal dynamic measured on the DOUT is 0-3.3v
The on the XBIB-XBP9XR-0 board we connect DOUT to DIN to simulate the loopback ( is this correct? can you please confirm?), but with the scope we see that the dynamic goes to 2.1-3.2v. Is this normal?!.. somehow the DIN pulls down the DOUT badly…
We tried to modify the pull/down config without results.

when using for example the XBIB-U-SS which has a loop back jumper, we can see that the dynamic of the signal on the DIN is the correct one, and all works fine.

We suspect that on the XBIB-XBP9XR-0 it is not correct to use the test point to shorten DIN and DOUT but there is no documentation available on this.
Can you provide this board schematics, and a correct setup?

update: we have also connected directly on the SX pro module pins ( no test points header) DIN and DOUT, and the issue still persists.


I would suggest restoring your module to defaults as I am not seeing this when I probe the test points. In all cases they remain at the correct voltages. Even with a jumper connected.

I have created a small video, apologies for the quality
have a look at https://www.youtube.com/watch?v=Rp9sgDD9NPg
please let me know what you think



This board does not support hardware loop back. You need to use the loopback cluster ID instead.

The reason for that is that you have two devices driving the same line. That is both the XBee module and the FTDI chip are driving the same lines.


I have also power sourced the XBEE #2 without USB cable.
Hence no FTDI should be used I guess, or ? and the behavior is unchanged


Regardless of how you power that board, the FTDI chip has power and is controlling the lines. Simply put, that board does not support a hardware loop back function. It only supports a loop back function done in software with the loop back cluster ID.