XBEE keeps pausing then sending big clumps

Keith Young · 2010-12-27 19:53

I have a 16 bit value I am sending from one Prop mounted XBEE to another.

I have yet to be able to get these XBEE's, whether Prop or PC mounted, to send a continuous data stream of sending the same 12 or 16 bit updated variable say 5 times a second.

Instead what I seem to always get, no matter what 100th way I code, some smooth data coming in, followed by say 4 seconds of nothing, then a sudden barrage of the past 4 seconds worth of data. It will then send smooth again for a short time untill repeating.

Is there a setting or specific RTS CTS thing I need to be doing? I'd like this to be smoothly sending a 16bit and 4 12bit values smoothly at 100 per second. That's only 6400bps and I have it at 9600 baud.

Tips?

Thanks,

Keith

Martin Hebel · 2010-12-28 10:13

Even though the data rate is 9600, there's no guarantees it can handle continuous data rates at that speed. There's a lot that has to happen to get data across. It may be a bad frame needing some retries and slowing things down, and it may be trying to packetize quickly incoming bytes.

A couple things you might try is to set RO to 0 (zero). This will prevent the XBee from trying to buffer data for a transmission, but send data as it arrives instead.

Another thing you can do is reduce overhead of acknowledgments back and forth by sending to the broadcast address ($FFFF), though it can lead to more packets not being received (no acks/retries).

-Martin

Franklin · 2010-12-28 10:14

How have you configured the xbees? What is your code?

John Abshier · 2010-12-28 15:07

>16bit and 4 12bit values
I would not be surprised if the 12 bit values are sent as two bytes. That is a total of 10 bytes and 10 bits per byte (need a start and a stop). At 100 per second that multiplies to 10,000; just a tad over 9600 baud.

Why stay at 9600 baud? On the Prop side, even simple serial will handle 19,200 and the PC can also go much faster.

John Abshier

Keith Young · 2010-12-29 22:55

The current code is

Receiver:

repeat
    DataIn := -1
    DataIn := XBE.RxTime(100)                         
    If DataIn == "!"          ' If start delimiter
      XBE.Tx("!")  
      shared := XBE.RxTime(250)
      !outa[4]         
      DBG.Str(String(16))                          
      DBG.Bin(shared,16)
      XBE.rxflush

Transmitter:

cognew(@entry, @Shared)
  repeat
    !outa[27]                  
    DataIn := -1
    DataIn := XBE.RxTime(100)
    XBE.Tx("!")
    if DataIn == "!"
      !outa[16]   
      'XBE.Tx("!")             ' Send start delimiter 
      XBE.Dec(Shared)
      XBE.CR

They are both configured as default, I just threw a PanID number in.

I am not against increasing the Baud, I just want to take one small step at a time getting this to work.

Keith Young · 2011-01-19 15:37

How do I put the UNSOLVED tag on the thread title?

Martin Hebel · 2011-01-20 04:41

Typically, when things are not resolved after having been given some suggestions, the poster provides feedback on what effect the suggestions have been tried, any effects of them, and other information. This allows others to evaluate further.

R · 2011-02-17 18:03

Roughwood, are you using series 1 or series 2 XBEE radios?

I am seeing this same issue with series 2 radios and was wondering if maybe it is a series 2 specific issue.

i182willsw · 2011-02-21 09:10

Hey the problem, which isn't actually a problem at all is in the xbee. You can change how full the buffer on them has to be before it sends the data. You will need to download X-CTU connect your xbee to the computer(via the explorer) and then go to modem configuration. I'm pretty sure you need to change the RO (packetization timeout) to a very low number or even 0. this makes it so that the xbee doesn't wait until it has x amount of data before sending.

XBEE keeps pausing then sending big clumps

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