Firmware for LEA-4T GPS logger. LEA-4T is a GPS receiver made by u-blox. This receiver can process L1-wave and output navigation data and raw data such as carrier-phase or psuedo-range in 4 Hz and 10 Hz, respectively. Nice!! This firmware drives a C8051F340 MCU made by Silicon Laboratories as a GPS logger with LEA-4T. All related hardware are published on https://fenrir.naruoka.org/archives/000569.html . You can get the schematics and PCB layout of the hardwaer in Eagle PCB CAD format from the above URL. If you want to build this firmware, only you have to do is just type "make". After "make", you can get executable binary in "build_by_sdcc" directory. The binary is downloadable with Silicon Laboratories IDE. The data recorded by this firmware whose file name is log.dat make sense in 32 bytes. The first byte of the 32 byes is a header byte and always 'G'. The remained 31 bytes are governed by the u-blox ubx protocol. This specification has compatibility with my another project, Super Sylphide, ( https://fenrir.naruoka.org/archives/000666.html ) which is making an autopilot system for small unmanned vehicles. The license of this firmware can be distributed under the license of Attribution-Noncommercial-Share Alike Creative-Commons. Please refer http://creativecommons.org/licenses/by-nc-sa/ when you want to know the detail. The copyright is inherited in fenrir (M.Naruoka). Finally, the firmwear is built with Tiny-FatFs, which is coded by ChaN. http://elm-chan.org/fsw/ff/00index_e.html I'd like to say thanks to him, and if you want to use this firmware, please also take the license of his code into your consideration (2007/11 now, he does not any restriction).