XBee-PRO 900HP RF Modem - RS485 Modbus routing over mesh?


I am wondering if it is possible to configure the
XBee-PRO 900HP RS485 RF Modem to handle serial modbus routing the same as the CPX4 is able to.

Basically, I would like to use one modem connected to the modbus master device and have it talking to multiple slave modems out in the field in a mesh network.


No, not in the same way as n X4 but yes in the same way as an Xtend or XStream RF Modem. That is, the 900 HP will act as a transparent cable between the master and the modbus slaves. Simply configure the 900 HP for a standard Point to multi-point configuration and let the Modbus devices communicate just like they are on a cable.

Broadcast - Default

DL and DH = the SL and SH of the base
Set MR to 3
MH to the max number of hops needed to reach the end
NH to the max number of hops needed to reach the end

Thanks mvut, that has set me on the right track. Is it possible to configure one unit as a repeater between the master and slaves?


Sorry to jump in on this topic.
I’m currently on the look out for a RF product from Xbee that can transmit modbus rs485, spec pretty much identical to Sams post above.

Over the last 2 weeks i have been passed around the Xbee organisation, America, France, India, Australia. and no body has given me clear feedback on what product to choose.
Last week one technician from Australia contradicted technical advice from another technician from India. Safe to say my head exploded with confusion.
I’m really hoping someone on here can help point me in the right path.

Ideally i’m chasing the module only device, Bare bones, no enclosure, so that rules out the Digi Xbee RF modem.
The product would be great if it was out of the box, meaning minimal configuration is fine, coding would be an issue.
I was liking the Xbee 900HP pro. but only just found out that it cannot transmit modbus on its own, i’m told it requires a MCU to convert the modbus to Uart ? ?

Reading this post you talked about the Xtend. is this a possibility.I looked up the Xtend and there has been some little talk of modbus affiliated with it.

I’m drawing blanks with this guys. I cannot believe that Digi as big as it is cannot actually provide technical support on its products.

Any help would be so so so appreciated.

Thanks in advance

What do you want to do exactly? Do you want to read I/O direct from the xbee module, or just use it as a communication interface between other devices?

Suprising there is little support or knowledge with using modbus with xbee as I can see so much potential in the industrial market for these devices.

Hello Sambo.

The goal is to have a master PLC connected RS485 to a Xbee module. this module then communicates across the air to other Xbee’s, connected to PLC slaves.

I have contacted Xbee and other the last few weeks spoken to people from 4 counties with no luck.

I have started this same question on another thread as to get the message/issue out for comment.
Mvu who is a Digi forum regular as advised i need to use a 3.3 cmos level shift to achieve the above.

I was hoping someone could point me to a pre assembled component/PCI that interfaces with Xbee and i can simply just connect the Rs485 wires and all works after a few tweaks on the configuration software.

I’m in Australia.any module that provides the longest range suitable for this region is what i’m looking for.

Any help would be appreciated.

Thank you

Hi Smithtek,

I’m also in Aus, and have done what you are asking with success.

If you want a packaged solution ready to go, this one will do exactly what you want:

If you want to keep it small, there are a selection of third party Xbee to RS485 adaptors out there so you can wire direct to your PLC serial port.

If you have a heap of end devices or want mesh routing I’d recommend the CPX4 or CPX2 as a modbus gateway for your master PLC / SCADA.

Can you please post some detail on the config you used. I’m a newbie on this forum so any help much appreciated. I am trying to do exactly as you have outlined. Two Schneider PLC’s currently communicating over a cable on RS485 Modbus RTU. All I want to do is add the radios instead of the cable. I have 2 XM-M92_4P-AA RF modems. I see the Master transmit data ok and that appears to be transmitted over the radio link, but I get no response from the slave. Any help appreciated. Many thanks

Its been a while now since I completed this project but from memory I used the radio settings as suggested by mvut.

Can your radios see each other from the xbee config software? thats the first step.

I found Modscan is really useful software for troubleshooting comms to your slaves, just hook a usb cable into your digi modem and you now have a serial port from which modscan can communicate with.

I’m sure digi would sell thousands more of these if they detailed modbus and dnp3 support a bit better!!!