GPS Module EM-406 SiRF III Receiver HELP !!!

[JettPilot]

I got the EM-406 SiRF III Receiver with Antenna from Sparkfun and put it inside my plane hooked up to my OSD display board. The GPS powers up and aquires the sattelites (evidenced by flashing LED), but the GPS board never seems to see the information from the GPS, I get the searching for satellite message even though they have been aquired :(

Does this GPS module defualt to the NEMA 0183 output that the OSD requires ? I have it hooked up correctly, but I do not have the board to program this GPS or change any of its settings, so whatever was in it from the factory is what is still in there. I have exactly what you see in the picture below... Any other ideas why this GPS unit might not work with a display board ?

JettPilot

[Unterhausen]

It could be in the proprietary mode for some reason. There is a program called SIRFdemo that will change it back and forth. Are you using the module bare, or do you have the eval board? If it's bare, is your circuit capable of taking 3.3v signals? The module wants 5v, but all the logic is 3.3v. And the module certainly will not drive a rs232 circuit by itself.

[skogsvargen]

I have the same module and it was default NMEA. I just hooked it up with a ttl-rs232 converter to my PC and it actually gave me position updates in my basement with only a small window in it. I used the SIRFdemo to verify the operation.

/Magnus

[docphi]

You need a TTL converter.

http://www.compsys1.com/support/docs/a232dbr4.pdf

[JeffElecRC]

What docphi said.

If you connected the GPS to the serial port of a computer through a level shifter, you would see the GPS spits out messages right away before it has lock. Thats one way of making sure the module is working okay.

Also, from a cold start it should take a couple minutes for it to get a position.

[JettPilot]

I need a TTL converter ! I guess the signal level out of the module itself is not enough to drive the Video Overlay Board......

It looks like the Eval Board for the sirfIII has serial level outputs, so I just ordered the Eval Board so that I can also program the thing if I need to.

Thanks docphi

Stupid Gravity, and Stupid low level signals !

JettPilot

[Tom Harper]

JettPilot,

I had the same problem. The input line to the GPS module has to be tied high.

Tom

[docphi]

I need a TTL converter ! I guess the signal level out of the module itself is not enough to drive the Video Overlay Board......

It looks like the Eval Board for the sirfIII has serial level outputs, so I just ordered the Eval Board so that I can also program the thing if I need to.

Thanks docphi

Stupid Gravity, and Stupid low level signals !

JettPilot


No prob. I removed the DB9 connector and wired it directly to my EMS-406. Works like a champ. :D

[brianhomer]

It could be in the proprietary mode for some reason. There is a program called SIRFdemo that will change it back and forth. Are you using the module bare, or do you have the eval board? If it's bare, is your circuit capable of taking 3.3v signals? The module wants 5v, but all the logic is 3.3v. And the module certainly will not drive a rs232 circuit by itself.

Why not you brought the evaluation board together. you can direct plug it in without trouble. Saving time to assembly the unit from components level. More concerntrate the algorithm and protocol can help much more

[Tom Harper]

I'm replying here because I can't figure out how to attach an image to a PM.

I was addressing the issue of the Sirf lll unit appearing to have no output. If the input is not held high the Sirf lll thinks it is getting an input that makes no sense. It responds with an error message instead of NMEA sentences. That can make the rcving board appear to not be getting any information. Tie the input high and the Sirf lll will start generating sentences.

The schematic I am using is attached. As you can see the output of the GPS module drives logic inputs to a UART and an RS232 driver. No problem with output levels.