From: Lenny <leonhard.neuh...@gmail.com> Reply-To: "beagleboard@googlegroups.com" <beagleboard@googlegroups.com> Date: Wednesday, July 23, 2014 at 3:39 PM To: "beagleboard@googlegroups.com" <beagleboard@googlegroups.com> Cc: <sun19920...@gmail.com>, <sun19920...@gmail.com> Subject: [beagleboard] Re: How to synchronize ADC sampling clock ？
> Hi, > I never tried to read several ADC channels "simultaneously", but as far as I > understand the TRM section on this, there is really only one hardware ADC > witht multiplexer to make 8 channels. One acquisition takes at least 15 ADC > clock cycles (625ns), that is for 6 channels, you would have to read one value > after the other, giving you a 625 ns delay between subsequent values and a > maximum 6-channel-samling rate of 1/3750ns = roughly 250kHz. As said above, > jitter won't be too much of a problem here. Since the readout of the FIFO > buffer also induces some delay, you should more realistically consider 200-250 > kHz. > So if you can tolerate the delay of digitalization of the different analog > inputs, the integrated ADC will work, otherwise you should consider using an > external ADC. You could also use a small FPGA to do the data ack, time synchronization and time stamp the buffer like they do in ZIO. http://www.ohwr.org/projects/zio It is also possible to do this with IIO and there are examples on Analog Devices website for doing high speed data ack. https://wiki.analog.com/resources/fpga/xilinx/fmc/ad-fmcjesdadc1-ebz Regards, John > > > > On Wednesday, July 23, 2014 9:07:52 PM UTC+2, sun19...@gmail.com wrote: >> Hello, Lenny, >> your solution is good, thanks. Here is another question : is it capable of >> synchronizing "multiple" ADC channels at one time ? >> >> I have read ADC driver limitation from TI : >> http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver%27s_Guide#ADC_Drive >> r_Limitations >> >> and you said that I can use the ADC in single-acquisition mode. -> Is it >> capable of synchronizing "multiple channels" at one time? (because I need to >> sample three-phase current and voltage signal, so the sum of them are 6 >> channels.) >> >> I am not sure "single-acquisition" is limitation of hardware (ADC) naturally >> or just limitation of driver function? >> If I use single-acquisition mode, then I need to consider the effect of >> conversion time between one channel and another channel. >> >> >> Finally, If I could, please send your sample code for me to my gmail. >> Thanks! >> > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
