GPS Flight telemetry

[Rris]

I've ordered one of the sparkfun Venus solutions with the 636 chip on it (hoping to receive 638 from SkyTraq) to develop against, as well as some other sensors that i don't have. We've been umming and arring over this project for too many years! I'm going to start working on this seriously now testing various components and then working on PCBs.

Daniel - John said something about you laying a PCB that could be useful for balloon... was that the tracking board?

[Daniel Wee]

If the 638 is pin-compatible with the 636, you could just replace the chip and save yourself developing a new-board. Fingers-crossed.

Not sure but I don't think John has a full grasp of the project as yet so he may be just saying.

Daniel

[chris1seto]

The SUP500F, unfortunately, has dismal performance (cannot acquire at all.) Nate at SFE has posted that they no longer encourage people to use the SUP500F for the myriad of issues related to its' performance. The reason for this is unclear though but if could be a poor antenna design, or as you suggested - interference.

I questioned SFE's engineers directly about the interference issue, and they confirmed that was the major problem with the unit.

If you don't mind me asking, what active antenna did you use with the Skytraq Venus 6 devboard?

I have been getting very good results using this:
http://www.sparkfun.com/products/464

[Rris]

http://www.sparkfun.com/products/177 is what i have coming. I think daniel has the same?

[chris1seto]

http://www.sparkfun.com/products/177 is what i have coming. I think daniel has the same?

I prefer this one, http://www.sparkfun.com/products/464

From the datasheet:


Does your GPS antenna have FOUR RUBBERS?

The only issue I have heard about with that antenna is that the unit happens to be rather fragile near where the coax cable connects to the antenna.

[Daniel Wee]

I used something I purchased locally. Can't remember the brand now but I suspect almost any external antenna would perform very well.

Daniel

[Rris]

Venux 634 and 638 have the same land pattern, except 638 adds a ball grid array to the bottom. This adds extra ground points and what appears to be a SPI interface (from only looking at the pin labels).

So, if we design for the 638 we can still use the 634 on it no problems.

[Rris]

Sorry for replying late, had a very busy trip outside Taiwan last week.



SUP500F has poor performance at 10Hz due to self-interference coming from the chipset CPU. 5Hz performance is somewhat degraded, 10Hz is much degraded. Venus638FLPx will still have the same problem if making into something like SUP500F and running at 10Hz. If using active antenna that is at some distance away, then there is no problem.

Straight from SkyTraq. Waiting for info on getting Venus638FLPx chips.

[Rris]

Full datasheet for 648 modules
http://www.giga-concept.fr/media/upload ... DS_v02.pdf