I am having trouble with the GPS. I bought a second one because I thought the first one was defective, but it is exhibiting the same behaviour.
Using the olimexlpc2148 to interface. I have not even connected RX or TX yet. I connected power to the 3.3v on the lpc2148 board. I connected both grounds on the GPS to the ground on the lpc2148 board. When I power on, the GPS LED will flash once and then delay like up to a minute. Then it comes on and stays on. There is no blinking of the GPS LED. When the LPC2148 is running, I have a small LED flash program running. After the delay on the GPS, and the GPS LED comes on and stays on, the LPC2148 stops running and its power-on LED dims.
The voltage measured during the fix delay is 3.26v. after the fix, the gps blinks a few times, then goes solid red. the olimex board stops running, and the power on LED is dimmed. the voltage becomes 2.5v at this point. During the fix delay, current cycles between 0.9mA and 2.5mA. After the fix, in the moments the gps blinks, the current jumps over 99mA (my little rs dmm only goes to 99.99mA). When the GPS led goes solid, the current is 0.5mA, and at this point everything is hosed.
The GPS is powered with a 3.3v source off of the olimex lpc2148 board. I am powering the olimex board with the arm usb jtag gizmo. I have been wondering since last night if the issue is the usb power source. Pin 1 is power, pin2 rx, pin3 tx, pin4 and pin5 are ground. I have pin1 going to olimex 3.3v, pin 4 going to olimex ground. I have not connected anything else. I don’t have another 9v power supply available to test at the moment.
The locosys gps I am using is the 5 pin variety (…31). I don’t know where vbackup is on this device. I did see a v backup in the docs for the 6 pin version (…33).
I would check the specs on the JTAG to see how much current it can source because it sure sounds like it is not enough. I believe given the right power supply, the voltage regulator on the Olimex board can source ~800 ma, so that should be plenty.
I am leaning towards the possibility of the USB power being the issue. Trying to source a new power supply to borrow from work to try things out at home. will post results this weekend.