Any real GPS technology experts here??

[Chris Wilson]

I run a Motec mappable engine ecu on a couple of circuit race cars. This ecu accepts an input from a GPS receiver, and logs the co ordinates in memory. A data analysis package from Motec then draws a track map showing the cars position and a GPS speed etcetera. I currently use a 5 Hz Garmin receiver called a GPS18x-5Hz the technical spec is in this Garmin paper:

 

http://www8.garmin.com/manuals/GPS18x_TechnicalSpecifications.pdf

 

Motec charge a fortune for this obsolete Garmin unit that they sell ready terminated in a Motec box, I purchased an unadulterated Garmin one from Ebay for 1/3 of the price and just put a Deutsch connector on it, and it worked fine straight out of the box.

 

Motec also list faster updating receiver units, these being with a separate antenna to the receiver itself, the best of which seems to be 20Hz, see screenshot of catalogue page at:

 

http://www.gatesgarth.com/motec.jpg

 

These are extraordinarily expensive, being £1200 UK pounds, about $1940 US Dollars. Given I am doing this on a tight budget, could I purchase something that will work the same, maybe not in a nice die cast box, and save myself a lot of money? Can anyone suggest devices to investigate that will communicate by RS232? I doubt I can get or work out the Can Bus info to read a GPS Receiver by that means. I can probably get more info on the protocols the Motec ecu expects, they have a webinar on using GPS that explains this, but the little self contained Garmin GPS18x-5Hz worked fine "as is" by RS232.

 

Thanks for any help here.

[Ian C]

I think JustGav is probably the closest we have, although he's more of a mobile phone expert. Might be worth dropping him a line in case he missed this

[SimonB]

Can't help with the rest of it, but I know GPS receivers use a standard protocol called NMEA. I believe Motec requires that the GPS supports a particular subset of the main standard which I expect most units probably do. I think they also require you use 19,200baud for serial. So you may find a 20Hz GPS can't actually transmit its position quick enough at that rate, not sure.