SiRF or NMEA
hello all, whats the difference between these to protocols and which is the best to use? |
Posted 10:11 13 déc. 04 by mlc1967 (Technical Manager)
From the PocketGPSWorld website Brief Introduction of SiRF and NMEA Connecting to the GPS Receiver is the first hurdle to overcome, but first a brief introduction. Firstly there are two GPS Standards, NMEA and SiRF. Although SiRF is the up and coming new boy on the block, NMEA is the acquired standard and one used by 95% of GPS applications. Why two standards ? NMEA is getting old, it was designed to talk at 4800 baud (4kbps). Modem speeds today are 56kbps so you can see NMEA is slow. SiRF has brought about that change by increasing speeds and utilising full serial speeds up to 115200kbps. The thing is although NMEA is slow, some GPS Receivers will work at higher than 4800, but this is what NMEA prefers. The amount of GPS data sent down the serial port is very small and can easily be transmitted in 4800 baud so although you could reach higher speeds, there isn't really any necessary to do so. SiRF uses higher speeds because it can transmit the data quickly and put the processor into a wait state which in theory means it utilises less power, newer SiRF chipsets like SiRF IIe also have low power consumption which help even further with sustaining power to the GPS Receiver. -- Michael - eXpansys |
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