Hi everyone,
I designed a custom board which combines an MSP430G2553 SMD and a GPS based on MT3339 like this one : http://www.adafruit.com/products/790
I tested the combination on a launchpad and after building my own routines to be able to drive it with a very low RAM footprint (13 bytes buffer + variables you want to store) everything seemed to work well. But when I tried my board, GPS could not get a fix. Serial link is okay, but after a bug tracking I found where was the bug : when the mcu is not sleeping, even wtih a blank program, the GPS cannot get any satellite signal. When he is sleeping, it's ok. During this last tests, of course I used and external TTL serial <-> USB converter to control the GPS. Most of pcb under GPS is a ground plane. Moreover, I tried to connect GPS away from my PCB, wire by wire and I was ok. So there is a perturbation somewhere ...
I will post photos soon (and the rest of my work of course when I will be done) but if for now someone has any idea ...
To resume : GPS connected away : OK GPS soldered on board, MSP active (blank loop() ): not OK GPS soldered on board, MSP not active (sleep() ) : OK Regards