The DPH153-AT Femtocell - GPS power

I'll note here that I get position lock much faster and more reliably with the antenna pointed up at the sky (i.e. with the board positioned as it would be if it was in its case sitting upright on a shelf). This is true even (and especially) inside in my workshop.

Even after gaining access to the MIPS RA2150 chip, when I think about it a little, that is of little interest. I could repurpose this device as an NTP server if I wanted to go through the trouble of putting my own software on the MIPS, but I don't really need one. I have nice ARM boards that cost me $10 or less with faster processors and nicer GPIO and a nicer development environment. Hence, why screw around any more with this 10 year old gadget.

But it has been fun and a great opportunity to learn some things.

The question then is what power does this GPS chip get and how. This is tricky to evaluate given that this is a multilayer board.

The board itself develops 4 power supply voltages from the 12 volts given to it:

• 1.2 volts
• 4.0 volts
• 3.3 volts
• 1.5 volts

The SiRF chip datasheet says that it wants either 2.85 or 1.2 volts.

In the SiRF section, the top and bottom planes are ground and there definitely is 3.3 volts available on pin 1 of the GCON1 connector.

Experiment with cutting power supplies