What would be the best setup for my XBee 900HP network ?

XBee & XBee Gateway XBee - DigiMesh
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1

Hi,

I’m going to build a 900HP network that will have up to 500 end devices in the future (right now only about 100).

I’m using both the

  • XBP9B-DMST-002 (XBee-PRO 900HP (S3B) DigiMesh, 900MHz, 250mW, RPSMA, 200Kbps)
  • XBP9B-DMSTB002 (XBee-PRO 900HP (S3B) DigiMesh, 900MHz, 250mW, RPSMA, 200Kbps, 32K Programmable)

These end devices are mobile GPS units that are placed in vehicles moving only in a delimited area.

Also i’ll have fixed solar stations that will gather sensors data using a 32Kb programmable 900HP.

The fixed stations will be placed every each ~5 Km (depends on the XBee range tests that i will make).

The vehicles must send data using the nearest fixed station. And the final destination of every vehicle and fixed devices data is a main computer that will centralize, organize, cache, and send all the data to the internet.

I’ve read the XBee documentation but i still don’t have all the parameters defined, here are some considerations:

  • I thought about using DigiMesh, not sure why. (Maybe i should think of P2MP ?)

  • I will use the 200 Kbps firmware (cause i need it for DigiMesh), although 10 kbps would be sufficient for me.

  • I want the fixed stations 32 Kb programmable modules to be remotely updateable (OTA).

  • I want every vehicle device (non programmable xbees) to be configurable and firmware remotely updateable (OTA)

  • The vehicle xbees are going to be placed in a generic board with a secondary mcu, and i’m going to program it to send GPS data from the vehicle thru the XBee network in programmable intervals (from 1 sec to 10 min), and they’ll do that autonomously (i don’t want the central computer to poll data from every end device cause it would take forever and also would generate unecessary overhead in the network). Problem: probably all the end devices are going to send it’s GPS data at almost the same time (cause it uses the gps time), unless i put some randomized miliseconds delay on the firmware.

  • I have not decided if i should use AT or API modes, which one do you recommend for my case ?

Do you have any suggestions, thoughts, recommendations about my setup ?

Thanks !

2

I would suggest using the Digi Mesh 200 K Code but use it in the Point to point mode (TO0x40). Also set the BH and NH to 1. Then just send a broadcast message out.

This will allow the closest nodes only to receive the packet.

1 Like
3

Hi mvut,
I cannot use Point-to-Point mode, because the fixed solar stations are going to be repeaters for the mobile end devices.
As explained in datasheet: “Point to Point/Multipoint (P2MP) - All messages are always
sent directly to the destination. There is no repeating of the packet by other nodes.”
MOBILE DEVICES -> FIXED STATIONS (REPEATERS) -> CENTRAL COMPUTER
and only if the Mobile devices are close enough:
MOBILE DEVICES -> CENTRAL COMPUTER

4

You see that is where you use the directed broadcast with repeater functionality in.

5

Hi mvut, only now i’m implementing the solution.

I’ve decided to use the 200 Kbps firmware in DigiMesh mode (0xC0) so deployment could be easier. But now i’m facing communication problems in lots of areas. I think that using the 10 Kbps firmware would be great for this problem, signal coverage would be much better. Do you think i can use the setup you suggested with the 10 Kbps firmware ?

6

Yea you should be able to.

7

Problem with directed broadcast is that there’s no ACK for the packets. I’ll have to stick with 200 kbps in DigiMesh mode.