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GRT GPS options

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rvtach

Joined: 28 Jan 2008
Posts: 26
Location: Tucson, AZ

Posted: Tue Aug 23, 2011 8:02 am Post subject: GRT GPS options

Hi all-



I am installing my GRT Sport EFIS which I purchased without the internal GPS option. The Sport has the capability of accepting GPS data via a serial (single wire) input. I'm a working guy, paying as I go and so I'm trying to find a cost effective way to accomplish this. 



What I had proposed was to use one of the el cheapo USB GPS recievers (NMEA, hockey puck style for $40 to $60) to provide GPS data to the EFIS. An example would be the Globalsat BU-353. I found a USB jack with 10" leads attached that I would wire for 5 volts (to power the receiver) and run the DATA OUT wire from the receiver to the EFIS. I would just leave the DATA IN wire disconnected. I thought this was a promising idea.



I have been corresponding with GRT for 2 days now and they say my plan won't work because USB uses 2 data wires and the Sport needs it's data over a single wire. They suggested one of the Garmin handheld aviation GPS's. But when I look at the manual for the 396 (just for an example) it shows that there are 2 data wires (one IN and one OUT) just like the USB device! The Garmin manual shows that the DATA OUT wire is all that is routed to an "autopilot / NMEA device". Both GPS's are NMEA compliant.



So, it seems like my solution isn't completely out in left field (maybe?). But there's a whole lot that I don't know about this so I'm hoping someone who's more electrically astute than I am can help me get clear on this. I'm lost now. If this type of GPS receiver is not appropriate then any suggestions for one that will work would be very much appreciated.



Thank you all so much for everything I have learned over the past 8 years of being a fly on the wall of this group!

_________________
Jim McChesney
Tucson, AZ
RV-7A Flying

tim2542(at)sbcglobal.net
Guest

Posted: Tue Aug 23, 2011 8:53 am Post subject: GRT GPS options

On 8/23/2011 9:02 AM, rvtach wrote:

 	  Quote: 	
		   



 Hi all-



 I am installing my GRT Sport EFIS which I purchased without the internal GPS option. The Sport has the capability of accepting GPS data via a serial (single wire) input. I'm a working guy, paying as I go and so I'm trying to find a cost effective way to accomplish this.



 What I had proposed was to use one of the el cheapo USB GPS recievers (NMEA, hockey puck style for $40 to $60) to provide GPS data to the EFIS. An example would be the Globalsat BU-353. I found a USB jack with 10" leads attached that I would wire for 5 volts (to power the receiver) and run the DATA OUT wire from the receiver to the EFIS. I would just leave the DATA IN wire disconnected. I thought this was a promising idea.



 I have been corresponding with GRT for 2 days now and they say my plan won't work because USB uses 2 data wires and the Sport needs it's data over a single wire. They suggested one of the Garmin handheld aviation GPS's. But when I look at the manual for the 396 (just for an example) it shows that there are 2 data wires (one IN and one OUT) just like the USB device! The Garmin manual shows that the DATA OUT wire is all that is routed to an "autopilot / NMEA device". Both GPS's are NMEA compliant.



 So, it seems like my solution isn't completely out in left field (maybe?). But there's a whole lot that I don't know about this so I'm hoping someone who's more electrically astute than I am can help me get clear on this. I'm lost now. If this type of GPS receiver is not appropriate then any suggestions for one that will work would be very much appreciated.



 Thank you all so much for everything I have learned over the past 8 years of being a fly on the wall of this group!



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit



My suggestion is you get yourself an Byonics RTG  from  
	


http://www.byonics.com/mt-rtg.

You can then pull or "TEE" the serial data off for your second GPS 

source and have a cool APRS install in the process. There is a ton of 

info on this at VAF or just google it . You will need a TECH  (HAM) 

license to use it but you can almost buy the license anymore is so 

simple. Test questions are on the web and its a simple matter to get the 

license.

Tim

 	  Quote:

david.nelson(at)pobox.com
Guest

Posted: Tue Aug 23, 2011 10:05 am Post subject: GRT GPS options

Hi Jim,



As you've pointed out, the Globalsat BU-353 uses USB.  In this sense, the USB 

connection is providing both power (+5V and GND) and data (differential voltage 

signals).  That's great for a PC w/ a USB port.  However, and I could be very 

wrong, the GRT Sport unit uses RS-232 serial ports for data - a completely 

different critter than USB.



To go from USB to/from RS-232, you need some kind of converter - they typically 

run about 3-25 USD (looking at Amazon.com).  That solves the data portion.  You 

still have power to contend with, however.  The RS-232 converters I mentioned 

don't break out any power leads that I'm aware of.



Staying with GlobalSat, they do have an RS-232 based unit (BR-355 GPS) with a 

PS/2 connector. Combine this with their BR305-RS232 and you now have RS-232 and 

power.  Problem is, however, that power is still 5VDC.



To Tim's suggestion - look at byonics.com and their GPS receivers - 

http://www.byonics.com/tinytrak/gps.php - in particular their 'GPS2' (69 USD) 

and 'GPAP' (25 USD) products.  If you're interested, this also opens the path to 

expand into APRS if at some time in the future you feel compelled.



Good luck,

 	 /\/elson

On Tue, 23 Aug 2011, rvtach wrote:



 	  Quote: 	
		   



 Hi all,



 I am installing my GRT Sport EFIS which I purchased without the internal GPS 

 option. The Sport has the capability of accepting GPS data via a serial 

 (single wire) input. I'm a working guy, paying as I go and so I'm trying to 

 find a cost effective way to accomplish this.



 What I had proposed was to use one of the el cheapo USB GPS recievers (NMEA, 

 hockey puck style for $40 to $60) to provide GPS data to the EFIS. An example 

 would be the Globalsat BU-353. I found a USB jack with 10" leads attached that 

 I would wire for 5 volts (to power the receiver) and run the DATA OUT wire 

 from the receiver to the EFIS. I would just leave the DATA IN wire 

 disconnected. I thought this was a promising idea.



 I have been corresponding with GRT for 2 days now and they say my plan won't 

 work because USB uses 2 data wires and the Sport needs it's data over a single 

 wire. They suggested one of the Garmin handheld aviation GPS's. But when I 

 look at the manual for the 396 (just for an example) it shows that there are 2 

 data wires (one IN and one OUT) just like the USB device! The Garmin manual 

 shows that the DATA OUT wire is all that is routed to an "autopilot / NMEA 

 device". Both GPS's are NMEA compliant.



 So, it seems like my solution isn't completely out in left field (maybe?). But 

 there's a whole lot that I don't know about this so I'm hoping someone who's 

 more electrically astute than I am can help me get clear on this. I'm lost 

 now. If this type of GPS receiver is not appropriate then any suggestions for 

 one that will work would be very much appreciated.



 Thank you all so much for everything I have learned over the past 8 years of 

 being a fly on the wall of this group!



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350324#350324

rvtach

Joined: 28 Jan 2008
Posts: 26
Location: Tucson, AZ

Posted: Tue Aug 23, 2011 11:10 am Post subject: Re: GRT GPS options

Tim and Nelson-



Thanks for the info. 



As to the 5 volts I may be able to pull that from the GRT Engine Information System which outputs 4.8 volts for excitation voltage or I can install a 12V to 5V converter from www.current-logic.com for $10.



I looked at the GlobalSat BR355 unit and will probably go with that but I would still like to learn how this works. My confusion is from the labels USB, RS-232, Serial etc. I sort of thought that USB was just the form factor for the plug/receptacle and that it doesn't really have any meaning with regards to the data that is transmitted. Is there a difference in the data supplied from the #3 pin of a USB GPS versus the data supplied from the corresponding pin (#5) on the PS/2 connector on the BR355 unit?



Thanks for taking the time to answer my newby questions!

_________________
Jim McChesney
Tucson, AZ
RV-7A Flying

ceengland(at)bellsouth.ne
Guest

Posted: Tue Aug 23, 2011 11:44 am Post subject: GRT GPS options

On 08/23/2011 02:10 PM, rvtach wrote:

 	  Quote: 	
		   



 Tim and Nelson-



 Thanks for the info.



 As to the 5 volts I may be able to pull that from the GRT Engine Information System which outputs 4.8 volts for excitation voltage or I can install a 12V to 5V converter from www.current-logic.com for $10.



 I looked at the GlobalSat BR355 unit and will probably go with that but I would still like to learn how this works. My confusion is from the labels USB, RS-232, Serial etc. I sort of thought that USB was just the form factor for the plug/receptacle and that it doesn't really have any meaning with regards to the data that is transmitted. Is there a difference in the data supplied from the #3 pin of a USB GPS versus the data supplied from the corresponding pin (#5) on the PS/2 connector on the BR355 unit?



 Thanks for taking the time to answer my newby questions!



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit

Try some of these for info:
	


 	  Quote: 	
		   http://www.google.com/search?aq=f&sourceid=chrome&client=ubuntu&channel=cs&ie=UTF-8&q=serial+vs+usb 

 <http://www.google.com/search?aq=f&sourceid=chrome&client=ubuntu&channel=cs&ie=UTF-8&q=serial+vs+usb>


	


USB is(are)  serial interface, but serial interfaces come in an almost 

infinite variety, while USB comes in only 3 common versions, that I'm 

aware of.



Charlie

tim2542(at)sbcglobal.net
Guest

Posted: Tue Aug 23, 2011 12:40 pm Post subject: GRT GPS options

On 8/23/2011 12:10 PM, rvtach wrote:

 	  Quote: 	
		   



 Tim and Nelson-



 Thanks for the info.



 As to the 5 volts I may be able to pull that from the GRT Engine Information System which outputs 4.8 volts for excitation voltage or I can install a 12V to 5V converter from www.current-logic.com for $10.



 I looked at the GlobalSat BR355 unit and will probably go with that but I would still like to learn how this works. My confusion is from the labels USB, RS-232, Serial etc. I sort of thought that USB was just the form factor for the plug/receptacle and that it doesn't really have any meaning with regards to the data that is transmitted. Is there a difference in the data supplied from the #3 pin of a USB GPS versus the data supplied from the corresponding pin (#5) on the PS/2 connector on the BR355 unit?



 Thanks for taking the time to answer my newby questions!



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit




	


I did just that, pulled the 5VDC off the EIS. Not flying yet but I know 

of others who have used this option with success.

Tim

 	  Quote:

david.nelson(at)pobox.com
Guest

Posted: Tue Aug 23, 2011 12:51 pm Post subject: GRT GPS options

Hi Jim,



Thanks for the link to the 12V -> 5V - I'm bookmarking that site; I like the 

packaging/mounting.



 	  Quote: 	
		   4.8 volts for excitation voltage


	


Is this for the fuel probes?



Personally, I'd go with the DC-DC converter approach and have a 5V bus to power 

future gadgets off of and not have to worry about this 'excitation voltage' and 

what its properties are.



 	  Quote: 	
		   My confusion is from the labels USB, RS-232, Serial etc.


	


Think of USB as a next generation serial bus for PC's.  It was developed to 

address hanging peripherals (mice, keyboards, printers, storage, cameras, etc) 

off of a PC.  More info can be found at http://en.wikipedia.org/wiki/USB



USB, as compared to RS-232, is very complex.  The signaling on the wires 

between the two is very different and non-compatible - hence the requirement for 

the USB/RS-232 converter (it's not a simple matter of just connecting the wires 

to the different pins as in the old serial DB9/DB25 converters).



There are tons of serial protocols.  The 'USB' and 'RS-232' labels define how 

the spec is applied.



 	  Quote: 	
		   I sort of thought that USB was just the form factor for the plug/receptacle 

 and that it doesn't really have any meaning with regards to the data that is 

 transmitted.


	


The USB spec spells out the connector, power, signaling, bandwidth, 

handshaking, topology, etc, etc.  Compare the USB wikipedia link above to the 

RS-232 wikipedia link:



http://en.wikipedia.org/wiki/RS-232



 	  Quote: 	
		   Is there a difference in the data supplied from the #3 pin of a USB GPS versus 

 the data supplied from the corresponding pin (#5) on the PS/2 connector on the 

 BR355 unit?


	


Yes. A huge, incompatible one. 

Before you buy - I'd confirm 100% that the RS-232 port on the GRT can be 

configured to what the GlobalSat will do.  For example: 9600 baud, no parity, 8 

bit data, 1 stop bit, etc (typically written as '9600 8N1' or something close to 

that).  Somewhere in the GlobalSat docs it should spell this out very clearly 

and if it's configurable and how to change it, if needed.  As an example, 

sometime ago, I was fooling around with an NMEA 0183 device and it took me 

awhile to figure out that my gadget was talking 4800 baud and I had assumed it 

was talking 9600.

 	  Quote: 	
		   PS/2


	


Oh wait ... You might need a PS/2 <-> RS-232 converter. From 

http://en.wikipedia.org/wiki/PS/2_connector



"The PS/2 keyboard interface was electrically the same as the 5-pin AT system, 

and keyboards designed for one can be connected to the other with a simple 

wiring adapter. The PS/2 mouse interface is substantially different from RS-232 

(which was generally used for mice on PCs without PS/2 ports), but nonetheless 

many mice were made that could operate on both with a simple wiring adapter."



It looks as if they are just just using the PS/2 connector out of convenience as 

it has this on their site: "8. RS232 interface connection port."  Oh, BTW, it 

does 4800 baud but no mention of 8N1; If they are true to NMEA 0183, then they 

are doing 8N1.



Let us know when you're ready, and we can walk you through the wiring.



Regards,

 	 /\/elson



On Tue, 23 Aug 2011, rvtach wrote:



 	  Quote: 	
		   



 Tim and Nelson-



 Thanks for the info.



 As to the 5 volts I may be able to pull that from the GRT Engine Information 

 System which outputs 4.8 volts for excitation voltage or I can install a 12V 

 to 5V converter from www.current-logic.com for $10.



 I looked at the GlobalSat BR355 unit and will probably go with that but I 

 would still like to learn how this works. My confusion is from the labels USB, 

 RS-232, Serial etc. I sort of thought that USB was just the form factor for 

 the plug/receptacle and that it doesn't really have any meaning with regards 

 to the data that is transmitted. Is there a difference in the data supplied 

 from the #3 pin of a USB GPS versus the data supplied from the corresponding 

 pin (#5) on the PS/2 connector on the BR355 unit?



 Thanks for taking the time to answer my newby questions!



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350341#350341

rvtach

Joined: 28 Jan 2008
Posts: 26
Location: Tucson, AZ

Posted: Wed Aug 24, 2011 5:24 am Post subject: Re: GRT GPS options

Nelson-



The 4.8 volts is for fuel probes but it sounds like a number of other GRT/RV guys have successfully used that output to power the GPS receiver. I will probably go with the converter anyway.



Thanks for the detailed explanation of serial/USB/RS-232. As to the PS/2 cable on the GPS I think you are right about that choice of plug being simply convenience. The tech guy at USGlobalSat (and their literature) said that the data output of this GPS is RS-232.



After I double check that the GRT will be able to accept what this GPS has to offer (4800 etc), I think that I'll be getting one of these and the 12V -> 5V converter (which will actually convert anything from 10 - 32 volts down to 5 V). I'll need to cut the plug off the GPS cable to get at the data and power wires and build my own connector from a DB9.



Can't thank you enough for taking the time to educate me on all this. The best thing about building a plane has been all the people who want to help. Maybe some day I'll have a chance to pay it forward.

_________________
Jim McChesney
Tucson, AZ
RV-7A Flying

Tim Olson

Joined: 25 Jan 2007
Posts: 2872

Posted: Wed Aug 24, 2011 6:04 am Post subject: GRT GPS options

Jim,



I used the BR-305 recently to interface with my ELT and my APRS.

http://www.myrv10.com/N104CD/upgrades/20110506



To power it, I just used a simple 3-pin regulator with a couple of

minor components, potted into epoxy, so it takes the 14V

aircraft source and makes it 5V.  It's a couple bucks to build

your own converter.



Personally, although the GPS works great, I wouldn't consider

it appropriate for EFIS use in that I think if you're going to

drive an EFIS you should strive to use higher quality components,

but I am an IFR flier.  If you're VFR only and aren't as

worried about reliability, then I guess you can go cheap.

I figured this one (under $50) was good enough to feed my

ELT, and since I can verify it's working properly with my

APRS tracking, it turned out pretty good.

Tim Olson - RV-10 N104CD

do not archive

On 8/24/2011 8:24 AM, rvtach wrote:

 	  Quote: 	
		   



 Nelson-



 The 4.8 volts is for fuel probes but it sounds like a number of other

 GRT/RV guys have successfully used that output to power the GPS

 receiver. I will probably go with the converter anyway.



 Thanks for the detailed explanation of serial/USB/RS-232. As to the

 PS/2 cable on the GPS I think you are right about that choice of plug

 being simply convenience. The tech guy at USGlobalSat (and their

 literature) said that the data output of this GPS is RS-232.



 After I double check that the GRT will be able to accept what this

 GPS has to offer (4800 etc), I think that I'll be getting one of

 these and the 12V ->  5V converter (which will actually convert

 anything from 10 - 32 volts down to 5 V). I'll need to cut the plug

 off the GPS cable to get at the data and power wires and build my own

 connector from a DB9.



 Can't thank you enough for taking the time to educate me on all this.

 The best thing about building a plane has been all the people who

 want to help. Maybe some day I'll have a chance to pay it forward.



 -------- Jim McChesney Tucson, AZ RV-7A Finishing Kit





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350417#350417

rvtach

Joined: 28 Jan 2008
Posts: 26
Location: Tucson, AZ

Posted: Wed Aug 24, 2011 6:50 am Post subject: Re: GRT GPS options

Tim-



Good advice and I agree wholeheartedly with your recommendation for a better GPS for flying in the clouds. I will be VFR only for a while with plans to upgrade to an IFR panel with the addition of a second EFIS and a Garmin 430/530 once I am able to save the funds to accomplish that.

_________________
Jim McChesney
Tucson, AZ
RV-7A Flying

david.nelson(at)pobox.com
Guest

Posted: Wed Aug 24, 2011 10:03 am Post subject: GRT GPS options

Hi John,



Sounds like you've got it figured out.  Holler if you've other questions.



 	 /\/elson



On Wed, 24 Aug 2011, rvtach wrote:



 	  Quote: 	
		   



 Nelson-



 The 4.8 volts is for fuel probes but it sounds like a number of other GRT/RV guys have successfully used that output to power the GPS receiver. I will probably go with the converter anyway.



 Thanks for the detailed explanation of serial/USB/RS-232. As to the PS/2 cable on the GPS I think you are right about that choice of plug being simply convenience. The tech guy at USGlobalSat (and their literature) said that the data output of this GPS is RS-232.



 After I double check that the GRT will be able to accept what this GPS has to offer (4800 etc), I think that I'll be getting one of these and the 12V -> 5V converter (which will actually convert anything from 10 - 32 volts down to 5 V). I'll need to cut the plug off the GPS cable to get at the data and power wires and build my own connector from a DB9.



 Can't thank you enough for taking the time to educate me on all this. The best thing about building a plane has been all the people who want to help. Maybe some day I'll have a chance to pay it forward.



 --------

 Jim McChesney

 Tucson, AZ

 RV-7A Finishing Kit





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350417#350417

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