GPS shield and EB-85A

Adafruit Ethernet, Motor, Proto, Wave, Datalogger, GPS Shields - etc!

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

GPS shield and EB-85A

Post by cheisey »

Hi, I am working on the GPS shield. I notice from the GPS selection guide http://www.ladyada.net/make/gpsshield/modules.htmlthat the EB-85A based chips require 3.3v, but it looks from the schematic http://www.ladyada.net/make/gpsshield/g ... 10_sch.png that 5v is going to pin 1 of EB-85A socket. Can you confirm that the incorrect voltage is going to the chip?

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: GPS shield and EB-85A

Post by adafruit »

"3.3-5V" means 3.3V or 5V

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

So I run the PWR jumper to 3.3v (across the board) or program one of the analog outputs for 3.3 v if I want to switch it on and off inside the program?

http://www.ladyada.net/make/gpsshield/gpstest.html

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: GPS shield and EB-85A

Post by adafruit »

no. the board works as is, just use the shield as its designed

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

I now see that the "GPS_PWR" switches the power on and off via Q1, but how does the 3.3 or 5v get selected for the GPS chip (pin 5 EM-406A and pin 1 EB85A)? The EB85A devices require 3.3v http://www.ladyada.net/media/gpsshield/ ... atalog.pdf .

jdl2001
 
Posts: 86
Joined: Sun Mar 08, 2009 12:53 pm

Re: GPS shield and EB-85A

Post by jdl2001 »

cheisey wrote:I now see that the "GPS_PWR" switches the power on and off via Q1, but how does the 3.3 or 5v get selected for the GPS chip (pin 5 EM-406A and pin 1 EB85A)? The EB85A devices require 3.3v http://www.ladyada.net/media/gpsshield/ ... atalog.pdf .
Nothing has to be selected. The EB85A works fine with 5v. The datasheet makes this pretty clear. It would also work with 3.3v but 5v is fine.

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

I actually want to use the FMP04 from Ohararap http://www.ohararp.com/products.html with an EB-85A connector. It has a 10Hz update rate and costs $25. It's based on the MediaTek MT3329 chipset.

After digging around, it looks ok with 5v.

I just don't want to fry the chip as soon as I turn it on.

jdl2001
 
Posts: 86
Joined: Sun Mar 08, 2009 12:53 pm

Re: GPS shield and EB-85A

Post by jdl2001 »

cheisey wrote:I actually want to use the FMP04 from Ohararap http://www.ohararp.com/products.html with an EB-85A connector. It has a 10Hz update rate and costs $25. It's based on the MediaTek MT3329 chipset.

After digging around, it looks ok with 5v.

I just don't want to fry the chip as soon as I turn it on.
For future reference, this should have been your first post, not your last. BTW, you made it harder by buying their board but you (I'm showing confidence) will eventually figure that out.

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

The FMV04 datasheet says 3.3v +-10%, so I will stick with 3.3v. This is a budget chip. Some of the more expensive chips have onboard regulation allowing a 3.3-5v range.

The default FMV04 baud rate is 38400. Once I set that, it works. The default sentences are $GPGGA (at 10Hz), $GPGSA, and $GPRMC . I haven't tried to change them.

One quirk is that the GPS only transmits when I have the USB cable plugged in. If I try to run it off a 9V battery, it transmits a sentence or two then quits. The supply voltage in both cases is 3.34v. I will investigate current.

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

I'll try tying RX to ground via a 10K resistor (I don't have RX connected). Just saw this advice in the Arduino troubleshootig guide.

cheisey
 
Posts: 9
Joined: Wed Feb 10, 2010 4:17 pm

Re: GPS shield and EB-85A

Post by cheisey »

The Arduino onboard 3.3v does not provide enough current for the GPS chip, which is taking 45-55 mA. I apply an external 3.3v supply on it, and it works perfectly.

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: GPS shield and EB-85A

Post by adafruit »

yes that is why the GPS shield has a 3.3V regulator on it. theres even a breakout pin you can solder to

wourmman
 
Posts: 2
Joined: Thu Aug 07, 2008 8:15 pm

Re: GPS shield and EB-85A

Post by wourmman »

Have been fiddling with the FMP04 from ohararp.com. Tried picking up the 3.3V from a pad on the shield. Still only get mostly "!" and occasionally a "*". Have tried baud at 38400 and 9600 (the latter is the default according to the datasheet). Anyone have a definitive fix? Else, another GPS module that's foolproof (USGlobalSat's is much cheaper direct from them)? Sigh.

Locked
Please be positive and constructive with your questions and comments.

Return to “Arduino Shields from Adafruit”