Hi,
I have a pair of Xbee XBP24-BSIT from Sparkfun. One (AT Coordinator) is hooked to my PC thru a max3232, the other one (AT router) is tied to a Copernicus GPS.
On the terminal screen of X-CTU I can see data flow but the NMEA string is missing about 40% data. Checking the GPS output without the XBEE link is absolutely correct.
I should be missing something in my configuration but what?
NMEA string out of GPS:
.$GPRMC,103454.00,A,4706.9308,N,00205.9579,W,000.0,000.0,250509,05.3,W,A*0D
.$GPGGA,103455.00,4706.9308,N,00205.9579,W,1,04,2.88,00014,M,049,M,*74
String out of coordinator:
.$GPM0330.00A06.9309N0005.95000.0000.05050905.3A09
.$GPGGA033.0006.9309N0005.950.0000M09MB
Looks like flow control to me Does your GPS support RTS/CTS signals?
felis:
Looks like flow control to me Does your GPS support RTS/CTS signals?
If the reporting rate is low (one per second?) and if the error/retransmit rate is low, I doubt it’s a flow control issue. The buffer in the XBee is large compared to the size of the NMEA messages.
stevech:
If the reporting rate is low (one per second?)
It’s one message per second, not one symbol. The first line in example above is 65 bytes and Xbee buffer is 90 bytes. In addition, there is packetization delay and polling interval.
felis:
stevech:
If the reporting rate is low (one per second?)It’s one message per second, not one symbol. The first line in example above is 65 bytes and Xbee buffer is 90 bytes. In addition, there is packetization delay and polling interval.
The Digi User Manual says the input buffer for the transparent serial port firmware is (as I recall) about 200 bytes. CTS goes false well before this buffer fills (data sent by the device or microprocessor connected to the XBee). The buffer empties as fast as the RF link can operate. In the absence of interference and weak signals, this is about 80-120Kbps, net, given the 2.4GHz MAC for IEEE 802.15.4 is 250Kbps raw link rate.
stevech:
The Digi User Manual says the input buffer for the transparent serial port firmware is (as I recall) about 200 bytes.
Do you have a page number? I can’t find this data in user manual; my number came from this page → http://www.digi.com/support/kbase/kbase … jsp?kb=180
felis:
stevech:
The Digi User Manual says the input buffer for the transparent serial port firmware is (as I recall) about 200 bytes.Do you have a page number? I can’t find this data in user manual; my number came from this page → http://www.digi.com/support/kbase/kbase … jsp?kb=180
I’ll try to remember to look when I’m at work tomorrow. The copy I have on my home PC is a very old version. Perhaps if you download the OEM manual for the XBee series 1 and search on CTS in adobe reader?
stevech:
Perhaps if you download the OEM manual for the XBee series 1 and search on CTS in adobe reader?
We are not talking about series 1 here ( and yes, series 1 manual has a number, 202 bytes ). On the other hand, manuals for series 2 and ZB doesn’t have any clues about TX/RX buffer sizes, besides the note that buffers are “small”.
felis:
stevech:
Perhaps if you download the OEM manual for the XBee series 1 and search on CTS in adobe reader?We are not talking about series 1 here ( and yes, series 1 manual has a number, 202 bytes ). On the other hand, manuals for series 2 and ZB doesn’t have any clues about TX/RX buffer sizes, besides the note that buffers are “small”.
guess you have to ask Digi. I would “assume” that it’s the same or better than series 1.
Did you have to feed any initialization strings to the Copernicus? I tried to just read the strings from the output pin, all I got was a flat 3.3volts.