SparkFun Forums

[Robertacr]

Hopefully someone else has had this problem and can give me some advice. I currently have the Venus GPS module with SMA connector and I love it. I can get fixes within 30 secs and I am able to change almost all the settings via the binary commands. However, I am not able to change the update rate which is the most crucial for my purposes.

When the command to change the update rate is sent I get a positive acknowledgment but nothing changes and I still get NMEA messages at 1 Hz. Like I said, I can change baud rate, adjust it so that I only get the $GPRMC messages (all I need), and even adjust the $GPRMC message update rate as long as it is less that 1 Hz (i.e. set the interval to 1 or greater seconds). Here is the message I am sending:

Code: Select all

A0 A1 00 03 0E 02 01 0D 0D 0A

The above code is to set it to 2Hz but that does not even work. I get the positive ACK but no change in the actual update rate. I have tried the other update rates with no luck as well. Also, before I send these I change the baud to 115200.

Any ideas on what to try? Are the binary codes for changing the update rate correct in the documentation? I send the binary message from the documentation to enable WAAS but never get a positive ACK. I'm at a loss for what to do now. Thanks in advance for the help!!!

Robert

[TRON]

Your set update rate command looks correct for 2 Hz operation. Are you making sure that the baud rate is in fact going into 115.2kbps?

From what I remember only $GPRMC and $GPGGA sentences can go above 1 Hz in update rate, all others will only do 1 Hz max.

Might want to issue a command to reset the sentence interval to all 0x01's for each of the sentences to ensure they're properly configured.

[Robertacr]

Tron, thanks for the suggestions. The baud is at 115200 because unless the Logomatic (what I am using as an interface) is set the same the messages do not come through.

I have also tried resetting all the intervals to 0x01's and that did not work. I am playing around with the order in which I request things because it seems some requests override others. For example when I changed the output to Binary it did it until I requested only the $GPRMC messages then it went back to NMEA. So far no luck with re-arranging things. I really wish the documentation was better.

This is frustrating because like I said I love this chip, if only I could get it to give me the 10hz!

Robert

[gm]

Robert,

I just tried it using SkyTraq and I was able to get the $GPRMC message to be sent out at 10 Hz @ 115200 baud, so it is possible. I also tested to see if the setting survived a power-on reset and it did.

Hope this helps,

gm

[Robertacr]

gm,

That does give me hope. I think I am going to hook it up to my computer and use skyTraq to see what I can do as that seems to do the trick for everyone. I'll post back if I can get things to work.

Robert

[gm]

I looked at the output from SkyTraq for setting a 10 Hz update rate and it shows the command as being

A0 A1 00 03 0E 0A 01 05 0D 0A

which corresponds to what the manual states. I am at a bit of a loss why it's not working for you.

[Robertacr]

Problem solved!!!

After some back and forth with the good folks at SkyTraq they determined that my chip was running off the internal ROM and not the Flash memory. They recommended checking to make sure pin 9 was pulled down. If pin 9 is left open or pulled high then the chip runs on the internal ROM which limits you to, you guessed it, 1Hz and your settings will not stay after power down.

I double checked the solder jumper on the board and sure as heck it wasn't connected properly. I swore I had checked it but apparently I had not (rookie mistake). After fixing the solder jumper and powering up the chip it works like a charm!! 10Hz, WAAS, settings remembered after power down....AWESOME chip!!

For those having troubles with this chip, symptoms of running off the internal ROM include: default of 4800 Baud (not the 9600 the documentation says), nav light blinks at 1 Hz relardless of signal (should be lit steady until signal lock when it flashes rapidly), settings not remembered after power down, and inability to get more that 1Hz update rate. Pulling pin 9 down fixes all this and you have a fantastic GPS chip.

I want to thank everyone here for your help! I really appreciate you taking the time to help me with my n00b error. I also want to let you know that the customer service at SkyTraq is AWESOME!! Even though I am just one hobbyist living on the other side of the world, they promptly answered all of my questions and were extraordinarily helpful. I highly recommend this chip to people not only for how good a product it is, but because the company makes it clear that they care about every customer and are willing to help out even the most confused rookies.

Robert