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SteveT last won the day on February 19 2015

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  1. SteveT

    Papilio lock-in amplifier?

    Ephemeris data is considered valid for 4 hours and changes every 2 hours. Data is broadcast at 50 bits/second and a complete frame is 1500 bits, so from cold it needs about 30 seconds per satellite to get a full set of data. Since they run in parallel then a cold start takes between 18 and 36 seconds.
  2. SteveT

    Papilio lock-in amplifier?

    Actually the GPS signal includes ephemeris data. Cold starts have to download a new copy of the ephemeris after locking on to the signal. Warm starts just need to lock to the signal, hence the reduced time. Locking on to the gold code only takes a second or two.
  3. SteveT

    General technical questions

    Note that pins D0-D13 on the Duo are 5V tolerant, so you can connect them directly to for example the address bus. If you need closer to 5V then something like this will do the trick
  4. SteveT

    General technical questions

    You're going to have to create a level shifter board to sit between the two (the FPGA is designed to work with up to 3.3V logic, the 6502 works at 5V). Other than that, you're good. You can use the RAM for anything you can think of, provided that it is fast enough and you have enough free gates on the FPGA for your design. At 10ns it's more than fast enough to feed a 6502, and adding page selection logic plus emulating the old FD controller isn't stretching the Duo's capacity (you could implement the entire Challenger in FPGA logic, including the 6502, and still have free capacity.
  5. SteveT

    Pmod Connector

    It looks fairly obvious to me. The wing socket at the back right (looking at the Duo from the top with the USB sockets towards you) does dual duty as a PMOD socket. Wings are normally 4x3, you drop the back row of the Wing socket and add the 4 new pins for power and ground.
  6. SteveT

    PS2 Keyboard on zpuino with computing shield

    You could start here Which should explain all you need to know.
  7. SteveT

    My DUO arrived today

    There was an update via Kickstarter saying that Seed Studio had forgotten to ship them with the first batch, and to contact Jack if you couldn't repurpose one from something else.
  8. SteveT

    My DUO arrived today

    Mine also turned up on Friday. I'm working on downloading ISE at the moment.