Wrong. 16 bit capture with LPT connection would mean max 1.5 Mbyte/sec or 786432 samples a second if no overhead is used. This would give you 3 samples pr period of a 262144 Hz waveform. That's 262 kHz people, not all that great. With USB2.0 we get to stuff 60 Mbyte/sec through the bus at max rate! This would give 31457280 samples a sec and 3 samples/period for a 10485760 Hz waveform. (That's 10 MHz people!) I'm talking of using a special trick where the content for the data-packet's are delivered directly to the USB2.0 interface by the ADC via a double banked, buffering at higher clock-speed, clocking data from buffer to transmitter faster than it wil arrive in other buffer. This would allow for real-time "packaging" of data for USB2.0 bus. Yes I know it's sneaky but it will work. With proper shielding and a good layout this should be possible in a rather small package. Worst case scinario is that I implement the buffer ini a FPGA so that I can test different solutions. I want to be able to look at and capture signals in the 4-5 MHz band at most. Not necessarily at 16 bit, here I agree that temporal resolution is more important because it will mean doubling the number of samples pr cycle. Besides, capacitance in my design is likely to distort signals so much that the extra resolution won't show any real information anyways... What I do need is info on different chips so I can find one that won't ruin me and still give me some power. KreAture ----- Original Message ----- From: "Olin Lathrop" To: Sent: Monday, January 20, 2003 1:22 AM Subject: Re: [PIC]: Interfacing a PIC to a computer via USB2.0 ? > > Anyone done this yet? > > I want to explore this as a first step in a high frequency, high data-rate > > capturing oscilloscope for PC. > > Using USB2.0 I would get a superb datarate and more than enough power to > > drive any chip for ADC. > > > > Accuracy isn't my goal, as in the previous oscilloscope project from > > piclist.com, I'm after visualizing data. > > To be able to view a pulse-train and debug communication based on that > will > > be sooo much easier than other means... And, most USB2.0 chips are, as > far > > as I know USB1.1 compliant too. Thus older comps can do captures at lower > > data-rates instead, meaning either bursts at full temporal-resolution or > > continous at lower temporal-resolution. Would be sooo great to have a > > single or dual channel oscilloscope you just cram in your pocket :-) > > I don't see the scope to host bandwidth as that much of a big deal. Your > capture bandwidth is what counts. You will have to capture to RAM anyway, > so uploading the data to the host can wait a few milliseconds. You only > need to send to the host what you can look at. A decent trace would be 1024 > points by 10 bits. Even packed into 16 bits this is only 2Kbytes. In > reality, I'd rather have a fast 8 bits than slower 10 bits. Either way, > upload traces doesn't sound like a bottleneck. > > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.