- From: Calin A. Culianu <calin_at_ajvar.org>
- Date: Wed, 2 Oct 2002 17:44:24 -0400 (EDT)
On Wed, 2 Oct 2002, David Schleef wrote: > inaccurate if you run it faster than spec. > > It may be simpler to think about it in terms of external triggering. > The board must latch on to the analog signal (on the correct channel) > within a few nanoseconds of getting the external trigger. This means > that the mux must already be settled on the correct channel. This > is most easily done by switching the mux to the next channel as soon > as the A/D converter latches. > Do I have to worry about this when using insn's to sample across channels? From the above paragraph it seems to me that it actually takes the board A/D-converstion-time + MUX-settling-time microseconds to successfully switch channels and return a digital pattern (lsampl_t) to comedi. So if I do the following: 1) INSN_READ on new channel with n=0 (to switch the MUX) 2) INSN_WAIT with data = MUX settling time in ns 3) INSN_READ with n=1 Aside from the time it takes the code to execute on the cpu, does 1-3 actually take ADC conversion time _plus_ mux settling time, or, like you said in a previous email, just a bit over mux settling time? What triggers the conversion internally on the ADC? Is it the physical act of reading the registers? Does the CPU then block waiting for a reply to it's inb instruction? I realize I am in a bit over my head on this one, as I am not usually a hardware guy (my formal training is in computer science, not EE :) ), but any help is really appreciated... Inquisitively yours, -Calin
Received on 2002-10-02Z20:44:24