How to achieve 80kb/s data rate with Xbee 868LP

XBee & XBee Gateway XBee - 802.15.4
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Hey everyone!

I am trying to get the maximum throughput from Xbee using API mode.

As i discovered, the maximum payload of a packet is 255 bytes. As i understand, the max payload depends on firmware and it isn’t changeable with AT parameters. Well it would be better if i could send larger packets, but i can live with that. Moreover, if the max payload is 255 bytes, the why the API frame supports 16 bit (65536 byte) packet length…

The real problem is the huge timeout when sending packets. For example when sending one 25 byte data packet, spi interface transmits data to xbee in ~20ms, but the time it takes for radio packet reach its destination is about 627ms.
For 200 byte packet it took twice as more - 1.2 sec.

I provided the screenshots with spi data from logic analyzer. 5th channel is spi-attn pin.

http://i694.photobucket.com/albums/vv308/krampis/25bytespacket.png
http://i694.photobucket.com/albums/vv308/krampis/200bytepacket.png

I tried changing RO parameter, but it changes only timeout for transparent (uart) mode.
I found that there is an %H parameter(MAC Unicast One Hop Time.) But to change it, i need to “Changing MAC parameters can change this value.” - change MAC parameter. And i couldn’t find how to do that.

Maybe someone has encountered the same problem or knows the solution?
Huge thanks.

2

First off, yes, there is going to be some delay and depending on the total number of channels you have selected and the number of hops will greatly affect that delay.

To stream data, you are going to need to use at minimum of 11 channels. The data is going to need to be in a Point to point association with both nodes being only 1 hop away. (BH and NH = 1). Your TO or Option bit for the API should be set to 0x40 (Point to point/multi-point mode).