SparkFun Forums

[caseyzahorik]

I'm using: https://www.sparkfun.com/products/10416

It's advertised having a max data rate of 250kbps but in X-CTU I can't configure it to have a baud rate of more than 115200. Any assistance on how to fix this would be greatly appreciated.

I would be glad to provide additional information or screenshots if needed.

Thanks!

[Valen]

You can't set a higher standard baud rate than 115200 because there isn't one. But you can (try to) set any specific rate in a wide range with the BD command upto 921600. The device may not actually work though with that setting. The endresult might be slightly off from desired due to clock divider ratio not allowing an exact match.

see page 136: http://ftp1.digi.com/support/documentat ... 0976_V.pdf

Or the baudrate of the other listener device might be slightly mismatched and prevent communication. Make sure you never save to non volatile memory with this unusual baudrate. It may brick your device.

p.s. never trust a max rating in a datasheet at face value. Key note is the word "advertised". The communication over RF is fixed at 250 kbits, so you'll never get that transmission rate out of the UART. But feel free to try ofcourse.

[stevech]

XBee series 1 (non-Zigbee) and series 2 (zigbee-only) use IEEE 802.15.4 as the MAC layer. In 2.4GHz, it's unlikely that you'll sustain a net of overhead bit rate of more than about 40Kbps. That's due to '15.4 in 2.4GHz being half duplex, with ACKs as a rule, and '15.4 as a single IEEE defined modulation rate.

The 250Kbps rate you will see is the raw frame burst rate ignoring overhead. Like 802.11 and other half-duplex CSMA/CA (CCA) protocols, the benefit of the fast burst coded rate is reduced on-air time for spectrum sharing and reduced collisions.

So 125Kbps for the UART interface to the radio is quite fast enough to fill the channel's net capacity. And the buffer capacity in the radios of S1 and S2 is limited so care must be taken to use flow control of one kind or another to avoid such.