Sending commands to a GPS module
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From: Piglit on 23 Jul 2010 21:52 I have a SSF2929P gps module which I wish to enable the ZDA string. If I apply power to the module it happily spits out data, finds sattelites etc and displays results on my terminal, but nothing I send to the module will stop the flow of data and put it into a mode to accept the commands. I'm beginning to think comms with this thing is half duplex, not full duplex. If this is the case, how do I reverse the flow and make it listen ? (Yes I do have Rx and Tx connected) Cheers M
From: Winston on 24 Jul 2010 02:15 On 7/23/2010 6:52 PM, Piglit wrote: > I have a SSF2929P gps module which I wish to enable the ZDA string. > If I apply power to the module it happily spits out data, finds > sattelites etc > and displays results on my terminal, but nothing I send to the module > will stop the flow of data and put it into a mode to accept the > commands. > I'm beginning to think comms with this thing is half duplex, not full > duplex. > If this is the case, how do I reverse the flow and make it listen ? > (Yes I do have Rx and Tx connected) > Cheers > M Apparently, anything that you send must be a valid NMEA - formatted string with a checksum at the end. Anything else will be ignored. Try: $GPWPL,4807.038,N,01131.000,E,WPTNME*5C http://www.gpsinformation.org/dale/nmea.htm see the entry that starts: "WPL - Waypoint Location data" So you get to format the string as a text file and then copy to comx: Please let us know how you progress! --Winston
From: Jamie on 24 Jul 2010 12:18 Piglit wrote: > I have a SSF2929P gps module which I wish to enable the ZDA string. > If I apply power to the module it happily spits out data, finds > sattelites etc > and displays results on my terminal, but nothing I send to the module > will stop the flow of data and put it into a mode to accept the > commands. > I'm beginning to think comms with this thing is half duplex, not full > duplex. > If this is the case, how do I reverse the flow and make it listen ? > (Yes I do have Rx and Tx connected) > Cheers > M most devices have a protocol you need to follow.... most have a CRC system to deduce error, and also, some have a way to get out/in data mode like in the olds of external modems... etc... YOu need to read the data sheet on it..
From: Winston on 24 Jul 2010 13:16 On 7/24/2010 9:18 AM, Jamie wrote: > Piglit wrote: > >> I have a SSF2929P gps module which I wish to enable the ZDA string. >> If I apply power to the module it happily spits out data, finds >> sattelites etc >> and displays results on my terminal, but nothing I send to the module >> will stop the flow of data and put it into a mode to accept the >> commands. >> I'm beginning to think comms with this thing is half duplex, not full >> duplex. >> If this is the case, how do I reverse the flow and make it listen ? >> (Yes I do have Rx and Tx connected) >> Cheers >> M > most devices have a protocol you need to follow.... Yup. http://www.gpsinformation.org/dale/nmea.htm > most have a CRC system to deduce error, and also, some have a way > to get out/in data mode like in the olds of external modems... > etc... > > YOu need to read the data sheet on it.. This one? http://www.element-14.com/community/servlet/JiveServlet/downloadBody/13410-102-1-42402/40.Sirf%20nmea%20ref%20manual.pdf :) --Winston
From: Jamie on 24 Jul 2010 16:45
Winston wrote: > On 7/24/2010 9:18 AM, Jamie wrote: > >> Piglit wrote: >> >>> I have a SSF2929P gps module which I wish to enable the ZDA string. >>> If I apply power to the module it happily spits out data, finds >>> sattelites etc >>> and displays results on my terminal, but nothing I send to the module >>> will stop the flow of data and put it into a mode to accept the >>> commands. >>> I'm beginning to think comms with this thing is half duplex, not full >>> duplex. >>> If this is the case, how do I reverse the flow and make it listen ? >>> (Yes I do have Rx and Tx connected) >>> Cheers >>> M >> >> most devices have a protocol you need to follow.... > > > Yup. > > http://www.gpsinformation.org/dale/nmea.htm > >> most have a CRC system to deduce error, and also, some have a way >> to get out/in data mode like in the olds of external modems... >> etc... >> >> YOu need to read the data sheet on it.. > > > This one? > http://www.element-14.com/community/servlet/JiveServlet/downloadBody/13410-102-1-42402/40.Sirf%20nmea%20ref%20manual.pdf > > > :) > > --Winston $PSRFxxx,x,x,x,x*xx<cr><lf> Is that what you're referring too? P.S. Make sure you send the CR and LF at the end.. and of course, calculate the CRC, and there are no spaces. I know the Doc's say Xor with characters between the $ and * how ever, they don't really give you an example. I can only assume they are Xoring each char maybe with FF and then summing.. Who knows. |