When I first did this I felt it was counterproductive. Having GPS accuracy, but then losing it by inserting a protocol for retransmission. That was improvedupon by using the 1pps signal output from my GPS.
But there was still lag, so for fun I set the GPS unit to only transmit data exactly at the 1 second epoch and transmitted it via a 433MHz module. Again, there was a small amount of lag, so instead of trying to tell the current time, I always had my timekeeping registers set 1 second (approx) ahead of the received GPS time, but delayed displaying them by "Current time + 1 second - transmission delay(lag)" seconds. No matter how bad the transmission delay was the time displayed on the times, specifically the point when the display shows the correct time, was always accurate. As for modules, I used 433 MHz FM units which were okay. If i were to do it again I would just buy the cheap ETRX2 Telegesis Zigbee modules, which can create a self healing mesh network, and which are cheap and reliable as well as having checksums built in for data integrity testing and automatic retries if the data transmission fails. The ETRX2 is probably overkill in terms of specification, but almost as cheap as any other module, with the added benefit of being bidirectional as well as giving huge ranges due to the ability of each unit to retransmit via mesh networking. Chris On Apr 8, 4:41 am, morrisodell <[email protected]> wrote: > Hi All, > > I'm sure this subject has been discussed here before but now I need > to pay attention ;-) I have made several clocks that use GPS receivers > to get a time reference. That's all very well but it does restrict > them to needing an antenna and being near a window. I want to build a > system to get the time signal from one optimally located receiver and > distribute it to my various clocks anywhere in my house or office > using a low power RF link. > > What I want is something that will accept the serial stream from a GPS > receiver and reproduce it at the receive end. 2 way communications is > not really required. > > Any suggestions? > > Morris -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
