Replies to This Discussion

Permalink Reply by Darren on May 6, 2011 at 3:22pm

Please confirm that with each test you changed the xbee configs with x-ctu and confirmed a good xbee range test with apm cli test and x-ctu before doing mavlink messages.

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Permalink Reply by Paul Mather on May 6, 2011 at 3:44pm

Confirmed baud change. Didn't bother with range test as that requires changing up a bunch of stuff on my desk. Still fails at 115200.

 

Here's a post with some directions if anyone wants to make it work at 115,200

http://www.jsjf.demon.co.uk/xbee/faq.htm#q9 but this has nothing to do with my GCS. This is a baud rate problem....and the wrong data is arriving at the serial port.

 

http://forums.digi.com/support/forum/viewthread_thread,7255

 

 

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Permalink Reply by Darren on May 6, 2011 at 3:47pm

I just wish I had a set of 2.4's I could confirm with... the 900's are working flawlessly

 

edit: HK, I do not insuate that its anything to do with your gcs

Permalink Reply by Grant Olivier on May 9, 2012 at 6:54am

Hi Darren, Just thought I would enlighten you a bit on baud rate and on-air data rate. The baud rate needs to be less than the on-air data rate you set your radio up to be otherwise your radio will not be able to keep up with the rate which you are sending data to it and you will have data on your link dropped. Now when you set up an on-air data rate you should keep this as low as practically possible because the lower the on-air data rate, the longer your range will be. Basically if you halve your on-air data rate you double your range. Thus maintaining a large link margin (the difference in signal strength between the receive signal strength and the receiver threshold sensitivity) is always desired to avoid loss of lock and data loss. So you would never want to run the data link at a rate much higher than what you actually need. Keeping a high link margin increases link availability typically 8 dB margin gives a 99.9% availability (If I can remember correctly).  

Thanks

Grant

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Permalink Reply by Paul Mather on May 6, 2011 at 3:56pm

Sorry, it won't let me reply again (max sublevels reached I guess). I'm ordering two 900Mhz XBees to confirm it works the other way around. In the reading I've done tonight, there seems to be a bug in the XBee firmware that's causing the problems at 115,200. This long post suggests that the problem has to do with clock cycles on the APM (actually the sending system) but if that were the case, it should fail at 115,200 regardless of the hardware.

http://forums.digi.com/support/forum/viewthread_thread,7255

 

So I haven't gone through steps to set 2 stop bits and try again at 115200.... but I guess that's the next logical step. I wonder where Kartik Chandrasekhar is and if he's even using 115200. I wonder if he's set his PAN ID's to match....or if there's some other setting having to do with the X-Bee's that's causing his issues.

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Permalink Reply by Darren on May 6, 2011 at 4:13pm

I'll send you mine if you want. If I had budget left, I would buy some 2.4's myself; as I hear these days folks are saying its ok around 2.4 radio gear. (freq hopping vs fixed i guess) but if all else failed I could fall back to using it on a 35/72hz radio and 900 video setup i have.

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Permalink Reply by Paul Mather on May 6, 2011 at 4:27pm

Thanks for the offer... I placed my order early this week but now it looks like it's showing it's not going to be in stock until the 13th... but it didn't show a backorder when I placed the order (curse you Mouser.com!!!)

 

I'm doing some more testing right now. I still can't get the 2.4 XBee to perform above 57600... I'm messing around with the USB baud rate to see when it quits.

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Permalink Reply by Paul Mather on May 6, 2011 at 4:55pm

I just did some testing and things worked via USB up to 230400. As soon as I went to 460800 things stopped working again....but I can't say for sure if my GCS will go all the way to 921600

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Permalink Reply by Darren on May 7, 2011 at 5:28am

I also found the 230400 cap on usb. Also noticed there is a 115200 max setting in arduino :)

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Permalink Reply by Paul Mather on May 7, 2011 at 6:50am

So with the 2.4 XBee, the only solution I read was to change the stop bits to 2....but then I find out that you can't change the stop bits on the XBee.... so I wouldn't call that much of a solution. So 57600 seems to be the max for that model.

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Permalink Reply by Paul Mather on January 3, 2012 at 12:16pm

Is this APM?

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Permalink Reply by Paul Mather on January 3, 2012 at 12:38pm

I have not tried recently. There was supposed to be a change made to MAVlink that they might have implemented.

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