Problem With GPS

Benno

Hi all

I recently bought a Parallax GPS receiver (28146). I've hooked it all up exactly as described in the PDF documentations (GND, +5V, SIO) to my stamp. However when running the sample program i get no results. (it simply says no gps connected). I've double checked all the ports are correct and the led is flashing on the gps.

I simplified the code down to the below to simplify it and double check everything but still get no response.

Can anyone help please? Much appreciated


' {$STAMP BS2e}
' {$PBASIC 2.5}


hardware VAR Byte
firmware VAR Byte
getinfo CON $00
baud VAR Byte
baud = 188

DEBUG ? baud
SEROUT 0, baud, [noparse][[/noparse]"!GPS", getinfo]
SERIN 0, baud, 2000, noserial, [noparse][[/noparse]hardware, firmware]
DEBUG ? hardware
DEBUG ? firmware
STOP


noserial:
DEBUG "no incoming", CR

sylvie369

If the red light on the GPS is blinking, you do not yet have a "lock" on the satelites and valid data coming in. Is the message you get from the sample program "Error: No response from GPS Receiver Module"? That's what you'll get when you do not yet have valid data.

The GPS should be able to get a valid signal eventually even if there's something wrong with your program. It will sometimes take surprisingly long to lock on. Try leaving it sitting with an open view of the sky for several minutes. Once you get a steady red light on the module, run your program and see what you get.

Benno

Thanks for the quick response

I should have mentioned that. I had left the unit in the open over 30m from any obsticals for about 20 minutes. The light turned solid red but no change to the message it returns.

I understand that means it has some lock but not enought for a fix. It was out there for over 25 min which surprised me as to how long it took.

Would it provide Hardware and firmware values even without a full lock though?

sylvie369

With the Parallax demo program I do get the "No response" error message, and no firmware/hardware data while the red light is still blinking.

Benno

I've left it outside in clear view of the sky for over half an hour now. Is it possible I've got a dud unit? The light now stays blinking red at all times.

SRLM

How is your battery level? It could be constantly resetting, which would explain the problem.

Benno

Its being powered through a voltage regulator by a 12V 4AH SLA battery that was fully charged before i put it outside multimeter shows a very stable constant 5V.

I have now got it to a solid red light but it has not changed from that in over 2 hours now. This has me rather confused

sylvie369

Benno said...
Its being powered through a voltage regulator by a 12V 4AH SLA battery that was fully charged before i put it outside multimeter shows a very stable constant 5V.

I have now got it to a solid red light but it has not changed from that in over 2 hours now. This has me rather confused

As far as I know, when it's a solid red light, it has a fix and should be transmitting data. It doesn't turn green, or anything like that.

Benno

I was under the impression the light turned green when it had a fix but i may be wrong. I'll try connecting to it if i can get it to solid red again (needs to be sitting on a wall on the outside of my complex to get this). Will see how it goes. Thanks for you help

sylvie369

From the documentation:

ParallaxDocumentationRobot#37 said...
Status Indicators
The GPS Receiver Module contains a single red LED (light-emitting diode) to denote system status. The LED is located in the lower-right corner of the Module. A white overlay on the Module’s printed circuit board is used to reflect the light from the LED, making it easier for the user to see. The LED denotes two states of the Module:
1) Blinking (both fast and slow): Searching for satellites or no satellite fix acquired
2) Solid: Satellites successfully acquired (a minimum of three satellites is required before the Module will begin to transmit valid GPS data)

So yes, a solid red light means you've got a fix. A green light means you've got radioactive waste on your GPS.

FearTurtles

Benno, I was having a simular issue with the same setup as yours. To fix it I change the SIO pin setting to 1 instead of 15 and moved the jumper to go from SIO to pin 1. As I type this I do not have a steady red LED but the testing program gives me the Hardware Version, Firmware Version, and indicates Signal valid as No. I'm in the house so the signal is flaky from the Sats. Even by a Westward facing window.

Tom C

Benno,

For correct operation of the Parallax GPS, it should not be mounted on the BOE breadboard area.

I had good success with the GPS when I had it on a servo cable that was around two feet long.

Just a thought.

Regards,
TCIII

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
If you are going to send·a Robot·to save the world, you·better make sure it likes it the way it is!

FearTurtles

Mine worked fine when I changed pin numbers. Benno's problem is that the GPS is not communicating with the BS2e chip.

Benno

Thanks for your help guys. I appreciate it. I cannot seem to get this gps to operate in "smart" mode it does not respond to anything. However by connecting the raw pin low as described in the manual i can get NMEA strings out of it which i guess i can use instead.

Tom C thats good to know someone else found that as well. when i mounted the gps on a breadboard about 20cm from the stamp it got a fix much faster. Must be vulnerable to interferance from something on the stamp. Will try and get ahold of a longer cable to see if it improves further.