Hi No Windows 7 driver signing issues with a serial port. USB can be a bit of a tangle that way, not as easy as it used to be.
Bob On Feb 17, 2010, at 7:20 PM, Bruce Griffiths wrote: > Lux, Jim (337C) wrote: >>>> I don't know if there's a FIFO in front of the UART (e.g. what if you get >>>> simultaneous zero >>>> >>> crossings).. but I would expect there is. >>> >>>> The "hard work" is in the zero crossing detector ahead of the FPGA. (and >>>> perhaps in the latching of >>>> >>> the ZCD inputs into the FPGA). >>> >>>> Given how long ago it was made, that FPGA isn't a huge one. >>>> >>>> >>>> >>> Using 8 flag bits (one per channel) together with the associated time >>> stamp is a little more efficient and very easy to do and it doesn't >>> require a FIFO to ensure that simultaneous zero crossings aren't missed. >>> >>> >> Still need the FIFO.. >> Say you got one zero crossing at 0x01000 and the next at 0x01001 (where the >> number is the 20 bits in hex).. you'd still be sending the characters out >> the UART for the 0x01000 crossing when the next crossing occurred 10ns later. >> >> If I were doing it today (and I have no idea how Steve built it 10 years >> ago), I'd do something like a character for channel number and direction >> (ascii 0 through 7 for positive going, 8 through F for negative going) and 5 >> characters for the count (in hex), followed by a carriage return. All >> printable characters, easy for testing, no hiccups with DOS or some device >> driver trying to interpret binary, etc. >> >> You've got 8 channels, each zerocrossing at about 200-300 Hz (the difference >> frequency is 123 or 124 Hz, so you get twice that many zero crossings), or >> about 1600-2400 messages/second. At 6 characters per message, that's about >> 10,000 characters per second, so you'd need a fairly fast UART to keep up. >> (OTOH, the article mentions dropping characters..) >> >> They might have only used one direction of zero crossing, which gets you >> down to the 5000 characters per second, which you might be able to squeeze >> into a 38.4kbps serial stream, especially if you go to a denser packing. >> But you'll still need a FIFO. >> >> Next time I see one of the FTL guys, I'll ask. >> >> Jim >> >> > A LAN, USB or Firewire interface may be more appropriate all are easy to > implement. > > Bruce > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
