A brief update for today:
The four CNC machined housings arrived this week and all of them make a nice fit as you can see in the photo (I masked off the LED opening with some tape to simulate the lens effect as those lenses were to small to be CNC'ed). I have been in touch with the housing manufacturer this week as well to iron out the last details of the drawings. They will start cutting steel upcoming week! Once that is done, I will visit them to take a look at the molds before we get our first parts.
I built three additional GPS modules this week as well and the new upload tool for A-GPS data from the manufacturer seems to work a lot better now. After having uploaded the latest A-GPS data to each of the modules, I have performed open/clear sky testing with the modules and am very happy with the results! Typical time-to-first-fix (TTFF) with A-GPS enabled is ~10sec average on a cold start. Average signal-to-noise-ratio (SNR) is ~42dB (note that both the TTFF and SNR numbers are open/clear sky numbers and can vary in practice depending on surroundings and GPS satellite strength). Performance is thus very good for such a small unit! After the antenna tuning process, we might gain a little more on the SNR, but we will wait for those results first before concluding anything.
I also had to place a special purchase order (PO) for the high brightness/low current bi-color LEDs this week as they only had 200 in stock (delivery is scheduled for September 15, 2008). As I thought the green/orange color combination was a little too ordinary, I have chosen a blue/red LED which looks really cool. The blue LED will be on as power-on indicator and the red LED will flash when searching for satellites (it will be off after a GPS lock is found). So while searching for satellites, the combined blue/red LED will flash purple. Power consumption of the LED will be a little less than 1mA when the module is tracking. The rest of the module consumes ~36mA while tracking for a total of 37mA for tracking.
Power consumption, size and performance have all been traded off against each other, but it looks like the final results are pretty good in my humble opinion!
The estimated-time-of-arrival (ETA) for the modules is still set for the end of September. Let's hope there will be no further delays; thanks everyone for hanging in there!
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