Cannot connect do XBee PRO S1 module

Hello there,
I am using 2 XBee PRO S1 modules. I want them to work in mesh. I am connecting to them using USB->Uart adapters and XCTU software (version 6.3.8). I can connect to the 1st module without any issues. The problem is with the second module, I cannot communicate with it using uart. Also, when the module is starting, the LED’s does not act like in the working module. The most concerning one is the ON led that goes off. here is the notation:

YEL LED: Associate/DIO5

The right module works correctly, the left one does not, here is a video:

What could be the case of this? I would appreciate all help.

Edit: I have noticed that the problematic module starts itself every couple seconds and goes off again. I can then find it in the mesh using the working module, screenshot:

Try turning off the sleep function. This product when you use sleep need to use a synchronous sleep with ALL nodes sleeping at the same time or not at all.

Thank you for answer. This is something I do not fully understand. I have set a device to sleep mode 7, 1 second sleep, 1 second awake. I have noticed that I can only communicate with the module via uart if it is not asleep, thats 50% of the time. Is that correct operation? For example, I have one module that is like 10 seconds asleep, 500 ms awake- I cannot communicate with it in order to reprogram it. Does that mean its a brick now? Also cannot access bootloader with my hardware, as I have no CTS/RTS.

Also, If the node is asleep, is there a way to wake it up by trying to discover it over the network? Because I have noticed that I cannot discover devices that are asleep. I am trying to figue out a topology for my digimesh devices. I wonder how to sync their sleep and communication time. Because from what I have come across so far, it seems I can only talk to nodes that are not asleep, please correct me if I am wrong.

That would be correct. You can only talk to the processor while the processor is on.

Think of it this way, when you are in a sleep state, the processor is powered off.

No, you can’t wake a module early over the air. The only way to wake a module early is by pressing its reset line or using cyclic sleep with Pin wake and driving the pin wake.

Ok, now I think I get it. Thank you very much for answers.

But I still have one problem- One of my Xbee’s is constantly asleep (probably in mode 7 or 8). How can I keep it awake, so I can connect with uart and reconfigure the registers?

If you use an interface board with the RTS, DTR, CTS and Reset lines connected, you should be able to re-write the settings via the UART. You may just need to force a new copy of the firmware on the radio to do it.

I could get an FTDI chip with RTS and CTS line. I cant use the reset line there I think. So if I understand correctly, in order to enter bootloader for this chip I need a device with dedicated software?

You simply connect reset to a push button switch which is tied to GND when active.

So as long as I ground the RESET pin I will be able to communicate with XBEE using uart…? That doesnt sound right.

Not that is not what I am saying. What I am saying is that if you want to be able to read the radio in XCTU and to perform firmware upgrades, then you need to have VCC, GND, DI, DO, DTR, and RTS connected. It is also a good idea to connect the reset line to a push button that is connected to GND. This way if for some reason you need to reset the module you can by pressing the switch.