Hi, I’ve ben tinkering around with a lassen IQ i have, but somwhow don’t seem to be able to get it to work correctly. Ive tested my program on another gps which outputs NMEA string and that works, which makes me assume I have a hardware problem or a faulty gps.
What I have connected to my lassen are 2 20k pullups on the 2 rx lines (wich are pullups), one connection to my uC from the txb (pin 5) wich goes through a 1k resistor, and the ground and power line. I also have the compact antenna connected.
I supplied 3.3 volts however I’m not getting any message that I can decipher from txb port, meaning no NEMA sentences. My program can decode GGA, RMC, and PGRMZ sentences.
When you say program, do you mean a program running on a PC or is this an embedded system? If it is a PC, you will need some hardware to change the CMOS levels coming from the iQ to the RS-232 levels expected on a PC. Or you can you use an FTDI chip to convert USB to serial.
If it is an embedded system, I will assume that it is also running on 3.3 volts. In that case, check to make sure that you have a common ground between the systems.
If all this fails, get a scope and see what is really going on with the TX line.
One problem I ran into using the iQ on our board that I did not take into account the the bottom was metal. This caused a problem because there were vias for my comm lines under the module and they would short. We had to put some tape to insulate the vias until I made a revision where I moved the vias and made sure they were away from the module. If this is not possible on your design then perhaps you need to look at [tenting your vias.