[ntp:questions] ESR looking for good GPS clocks

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Tue Mar 6 21:20:51 UTC 2012


Chris Adams wrote:
> What would be interesting would be to combine a timing
> targeted GPS module and something like an ARM SoC running
>  Linux and NTP, and then make the whole thing act as a USB
>  device (bonus points if it can be bus powered).
> Create a custom USB protocol between the device and ntpd
>  on the host to synchronize the clock (something along
>  the lines of the network protocol but minus the IP stack).
>
> I expect this would be more accurate than a typical
>  low-cost network clock, and more accurate than trying to
>  do NMEA+PPS over USB-emulated RS232.  For a server or
>  device with this as the only USB device, the jitter
>  should be fairly consistent, and the latency lower than ethernet.

Some of the SiRf chips have all they need to do that
 however unless you are SiRF OEM developer,
 having signed all the necessary non-declosures, ...
 you aren't going to get the source code
 & tools needed to reprogram the ARM chip.

e.g. 7 years ago, SiRf released the SiRFstarIIA, 32 bit 65 MIPS
 ARM720T, UARTS, CAN, USB, SPI, ATAPI/EIDE, DACs, GPIO,
 supports 128 MB of external SDRAM and 8 MB of SRAM/Flash;
 SiRFstarII GPS engine, SiRFstarIIe, SiRFDRive1/2,
 QNX Neutrino RTOS SDK, HorizonNav NavMate, ...

Is the market big enough for someone to pony up the cash
 for the current Chips' License Royalty Agreement, _first_ $50K?
 {or whatever CSR charges since they bought SiRF for $10mil in 2009}

Their most recent stuff supports WinCE, Linux, Android
<http://www.csr.com/products/137/sirfprimaii>
<http://www.csr.com/products/138/sirfstarv-architecture-and-sirfusion-platform>
<http://www.csr.com/products/36/sirfprima-and-sirfprimaauto>
<http://www.csr.com/products/42/sirfatlasv>

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