XBEE ZB Throughput and packet losing

Hi people,

I 'm trying to do a simple peer to peer communication using transparent mode and two Xbee ZB on 230400 baud (serial baudrate).

The packets have 98 bytes and when i send it I got lost of the last 14 bytes… ok, it’s more than max payload. So, I tried to divide in two packet, but when I send one followed by the second one I got lost bytes anyway!!!

That not make sense if the Xbee is a system with 250kbps of RFand up to 921 kbps in serial port! The user guide show a throughput like 35 kbps, so that means I can’t send more than 35 kbytes of data per second???

Thank you for make it clear for me

The closest an XBee can get to 230400 baud is actually 250000 baud, which is a difference of 8%. So if your host is in fact delivering 230400 baud they won’t be able to communicate reliably.

If you configure the host for 250000 baud things may improve. Otherwise, lower the baud rate. For more detail, you could hop over to the 802.15.4 forum where I have a pinned post on the subject of high baud rates.

The difference between the RF data rate and actual throughput is due to things like the overhead of packetization, and the need for acks and possible retries in transmission.

Quite a few people use 115200 baud, which also requires the host to be configured appropriately (see the pinned post again), but I’ve seen very little discussion of 230400. I’d be surprised if you really needed to go that high.

Also – note that 250Kbps is the data rate of the underlying radio network – the effective throughput rate of the Dig modules is quite a bit lower and depends on many factors (number of hops, network traffic, etc.)

This is discussed in the current version of the manual starting on pg 64.

ZB ain’t wifi …

Your information on the baud rate being off for the XBee ZB module is incorrect. It is only off on the 802.15.4 module and not the ZB module. The throughput is considerably less than the RF data rate the RF data rate is only the rate the two radios talk to each other. You need to take into account that this is a Zigbee mesh based product and it has specific timing requirements that must be adhered to along with max packet size limitations. So yes, in reality, the streaming limit between two modules in a Point to point connection is at best 35kbps. But if broadcast mode is used, the data rate will be considerably less.

vmut, thanks for pointing that out. The baud rate comments do indeed apply only to the 802.15.4 models, as I hope I’ve made clear when posting elsewhere.