anyone tried the Venus yet??
looks pretty sweet!!! 
great job sparkfun!!
corvette123:
anyone tried the Venus yet??looks pretty sweet!!!
great job sparkfun!!
I’ve ordered one and I’m waiting for it to arrive.
Could anybody confirm that the only way to talk to the unit is via the serial IO, and that the SPI interface should only be used for interfacing with an external memory?
Thanks
I’ve been playing with the module over the weekend and so far, I’m impressed with its sensitivity. I’ve gotten a lock inside my house within 38 seconds from a cold start and I’ve been able to track up to 11 satellites. The antenna I am using is an active Sarantel.
I’m pretty sure the only way to communicate with it is through the async port and the SPI port is strictly for data logging to an eeprom chip.
gm:
The antenna I am using is an active Sarantel.
Where did you get the active Sarantel antenna? I didn’t see those on Sparkfun.
I didn’t get it from Sparkfun. We use them at work. We buy them from [Jim Gary & Associates. I was also using it with a passive patch antenna today and it was working great! It has a bulit-in LNA that seems to be quite good.
I was measuring the current consumption and it was drawing about 70 milliamps when it was acquring but then it drops down to about 30 milliamps while it’s tracking.
All in all, I’m pretty impressed with it. Next project is to design my own GPS board using this chip.](http://www.jimdgrayassoc.com/index.htm)
jim D gray is a P.I.M.P !!!
theyve got some mighty nice things in that store…
but dont call too early in the morning cuase they hit the sauce pretty damned good there hahahahahah
but thats texas i guess…
its a whole nother country.
thats where all my ex wives live too.
Go ahead and say RTFM if you need to, but for quick evaluation purposes… all I would need is the FT232 (serial to usb) connected to the GND, TX, RX, VCC pins of the GPS-09133, correct? I’m assuming the SPI pins are for an optional SPI flash chip but what are VBAT, PPS, 1, 2, and 20 used for (i.e. why are they routed out)?
I’m hoping to make a cool sky map tracking the az, el, and SNR of all acquired satellites over time.
This was an interesting question so I looked. Sparkfun says it can be used with their BOB-00718 USB converter board. But isn't the GPS 3.3V and not 5V which USB uses? Looking at the data sheet for the FT232RL is shows that it has a 3.3V regulator and somewhere is says you can draw 50ma for you own logic.Falcon X:
Go ahead and say RTFM if you need to, but for quick evaluation purposes… all I would need is the FT232 (serial to usb) connected to the GND, TX, RX, VCC pins of the GPS-09133, correct?
The GPS-09133 appears to draw “~28ma”, which is the only number I saw. At first glance it looks like you could use either GPS-00177 or GPS-00464 antenna. They say 12ma. So 12+28=40ma which is below the 50ma so it looks like it should work.
So it looks to me like you could connect those two boards together for evaluation purposes.
The SPI pins are for a flash part. The other pins are brought if you decide to use them. However, it looks to me like the VBAT pin should be labeled 3.3V instead of VBAT. The schematic shows VBAT tied directly to 3.3V. So it looks to me like you can't use the external battery to save the volatile data. (i.e., you will have to do a cold start every time you turn it on)Falcon X:
I’m assuming the SPI pins are for an optional SPI flash chip but what are VBAT, PPS, 1, 2, and 20 used for (i.e. why are they routed out)?
Falcon X:
I’m hoping to make a cool sky map tracking the az, el, and SNR of all acquired satellites over time.
About this chip… I’m getting some null data
$GPRMC,181019.000,V,0000.0000,N,00000.0000,E,000.0,000.0,300709,N*7B
$GPVTG,000.0,T,M,000.0,N,000.0,K,N*02
$GPGGA,181020.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,0000*67
$GPGSA,A,1,0.0,0.0,0.0*30
Am I required to send commands to configure the chip, or is the chip supposed to start getting data as soon as it finds a satellite?
Am I just having bad reception issues?
Nevermind, solved just bad reception.
Is there a way to put it on sleep mode?
I want to make my project really energy conscious, so I just need to get an initial reading and then put it to sleep.
I read through the datasheet and couldn t find anything relevant other than the vbat pin which is tied to V so no powering it up and down fast.
Any suggestions?
is there ANY distributors carrying the BGA version of this chip???
that LGA is sooo… passe’…
errr oops its not the exact same chip…
but its close.
yes theres a BGA venus chip !!
I’m hoping someone can help me out…
I got one of the Venus634FLPx GPS IC’s. I knocked up a board with one of the SFE GPS Chip antennas and an FT232RL. Hooked it all up and plugged it in.
So far so good, I get the NMEA stream in the SKYTRAQ GPS Viewer software. However it doesn’t appear to be able to find any satellites. I reset it a few times and supplied initial position and time (part of the reset feature in the software) and woohoo, I started to get somewhere. I eventually got a good lock seeing 6 or 7 satellites with a DOP down to 1.5. This was out in the conservatory, so I disconnect it from the power take it in too see if I can get a lock indoors, no luck. Take it back out, now nothing, nothing, nothing?!? Argghh
The other odd behaviour I see is that most of the binary messages are OK, i.e. requesting the software version etc. However if I try to download AGPS data to the GPS it times out. The only way to get anything out of the GPS again it to power cycle it or use the reset pin.
Any help would be appreciated.
Arran
Low Power Mode:
They document it in the data sheet, look for a diode with battery backup. You need to keep power to the clock and SRAM for it to remember the position enough to start in a second or two.
To do a low power mode, you need to maintain VBatt above some low voltage - 1.2-1.5 volts or something, and it takes microamps so it isn’t hard. Then shut off 3.3v. It won’t track but will restart very quickly.
The problem is that on both SFBoBs VBatt is shorted to 3.3v.
(To Sparkfun - instead of a solder jumper shorted by default, you could put a schottky diode across the two - how expensive is the one they recommend in the data sheet? And do you know how hard it is to find an SMD diode to fit the shorting jumper?).
And Why it might take so long to start:
It needs power to remember the time and position for a fast fix. It doesn’t say this but it may take several minutes under a clear sky from a cold start since it has to download all the data from several visible satellites before doing anything.
In “low power mode” it uses two search engines, in enhanced it uses four. If it has no idea of where and when it is, it needs to scan the entire GPS band (remembering doppler) until it hears something, tune and compensate, and when it tunes the signal sufficiently search for another sat while another section downloads the ephemeris, all which can take a while (and it needs a lock - a good signal - to do the download). That is why there have “61 channel” when only at most 14 might ever be used - to scan and do a first fix much faster, i.e. with 60 channels all looking they can each search 1/60th of the band.
This is what AGPS will bypass and why it also needs to know where you are in some cases. The AGPS download is FTP so it might be a problem depending on firewalling or other settings.
One other “trick”.
You can get the ephemeris for a satellite - it will be valid for an hour or so (actually longer, but the satellite will go over the horizon and have to come back to be visible for it to be useful).
On the GPS Viewer it is called Get Ephemeris, which will save a log file.
There are binary commands to do the same thing.
If you then cold-start it, where it might normally take several minutes to get a fix, it should be able to do so within about 30 seconds.
Once a satellite has locked for a while, the ephemeris will be available and can be stored.
I don’t know the format of the AGPS file, but my guess would be that it is a compressed Ephemeris for all satellites.
And AGPS should be directly available but it will take some time to decode (anyone want to help? hint hint).
The Eph.dat can be obtained from (.netrc):
machine 60.250.205.31
login skytraq
password skytraq
macdef init
prompt
passive
binary
cd ephemeris
get Eph.dat
Or the equivalent ftp:// url
ftp://skytraq:skytraq@60.250.205.31/ephemeris/Eph.dat
Note ftp://skytraq:skytraq@60.250.205.31/ephemeris shows the directory with other files.
To the GPS, each ephemeris record is 86 bytes (see data sheet), and this file has many sets of 86 byte records. The early fields have satellite number and some kind of time or place value, and the groups are in sequence of satellite number for a given time/place. You will get nearby time values somewhere if you save the ephemeris for the satellites using the utility.
Other files there are for individual satellites at various times, or Eph_4.dat which seems to be a “ready to upload to the chip” file.
“od -tx1 -w86” shows the pattern on a widescreen.
So to convert a cold start (taking 5 minutes with limited signal, or 1-2 minutes even open sky) to a warm/hot start, it might just be uploading the right set of records or copying Eph_4.dat out the serial port to the GPS.
I will probably try to experiment, but others might also want to try.
Sort of comfirmed.
“cat Eph_4.dat >/dev/ttyUSB0 ; time nl cat /dev/ttyUSB0”
will get a fix in 15-30 seconds.
Without the Eph_4 (in my room but with good sky view) it takes 50-70 seconds.
Please forgive my ignorance on the subject… I’d like to connect the Sarantel passive helical to the Venus module. My patch antenna has a very high resistance between the center and ouside of the connector and the Sarantel antenna appears to be almost a dead short. How would I connect the Sarantel instead of the patch? I’d like it connected directly off the edge of the board. (despite my RF ignorance, I can solder well).
Thanks!