>I have a old data device that is spitting out TTL data at 10 MHz. >There's just a data line (no clock) but the edges clearly indicate >an internal 10 MHz clock. > >I'd like to do a continuous capture of the bits, for up to tens of >minutes, into a PC. That comes to about 1 GB of raw data. I can >handle the decoding of the bits in software after the capture is >done. This is a one-time experiment.
Assuming this is a single data line, that's over 1MB per second, more than a traditional parallel port can easily handle. There are no cheap ubiquitous means to get that amount of data into a PC. The methods that I know of are expensive, either in money or engineering effort, including: - Get a digital I/O card. There are few of these around which can support your required data rate. One that I used in the distant past is the ADLink PCI-7200; I suspect NI may have a few offerings. You may have to DIY a shift register to get the data from serial to parallel. - Get a fast analog I/O card, record the data (now several GB worth) and apply some DSP to recover the digital data. This looks like a roundabout way, but analog I/O cards are more common and thus easier to borrow for an afternoon. Again NI has a few, but something like the HPSDR Mercury (http://www.hpsdr.org/) might work too; I'm not sure if the Mercury FPGA code can do 'wide' baseband sampling yet. A variant of this scheme would include a shift register and a simple D/A converter to get the rate down. - Build a board that converts the data stream to Ethernet or USB. I know of no COTS solutions for this, although I suspect the HPSDR Ozy FPGA can be re-coded to handle this. - Build a standalone data recorder, either with a microcontroller or CPLD/FPGA. JDB. [currently working on the standalone data recorder for a data capture application] -- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lartmaker.nl/ _______________________________________________ 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.