GPS shield and EB-85A
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Please be positive and constructive with your questions and comments.
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GPS shield and EB-85A
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?
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Re: GPS shield and EB-85A
"3.3-5V" means 3.3V or 5V
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Re: GPS shield and EB-85A
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
http://www.ladyada.net/make/gpsshield/gpstest.html
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Re: GPS shield and EB-85A
no. the board works as is, just use the shield as its designed
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Re: GPS shield and EB-85A
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 .
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Re: GPS shield and EB-85A
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 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 .
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Re: GPS shield and EB-85A
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.
After digging around, it looks ok with 5v.
I just don't want to fry the chip as soon as I turn it on.
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- Posts: 86
- Joined: Sun Mar 08, 2009 12:53 pm
Re: GPS shield and EB-85A
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 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.
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- Posts: 9
- Joined: Wed Feb 10, 2010 4:17 pm
Re: GPS shield and EB-85A
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.
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.
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Re: GPS shield and EB-85A
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.
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Re: GPS shield and EB-85A
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.
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Re: GPS shield and EB-85A
yes that is why the GPS shield has a 3.3V regulator on it. theres even a breakout pin you can solder to
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Re: GPS shield and EB-85A
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.
Please be positive and constructive with your questions and comments.