Thank you very much for the info. Now I know it is quite involved. Saleae looks good and maybe I will give it a try..
On Friday, 28 February 2014 00:56:03 UTC+8, Ytai wrote: > > IIUC, you're not talking about an oscilloscope, but rather about a logic > analyzer. > > You basically have two possible routes: > > 1. Periodic sampling of digital inputs. Send either raw data of some > kind of compressed data over USB to the host, where the decoding of the > protocol will take place. You'd be bounded by the PIC clock rate (16MHz) > as > well as by USB bandwidth. My gut feeling is that raw 3MHz would not be > feasible, and certainly not on more than one channel. > 2. Decoding of specific protocols using the on-board peripherals (for > example, to sniff a SPI bus you'd need two SPI peripherals on the PIC, > both > acting as slave, one sniffing MISO and the other sniffing MOSI. You might > be able to hit peak data rates of up to 8MHz, as long as the average > throughput is low enough to leave you some CPU time and USB bandwidth to > get the data across. > > Both options are non-trivial and require some amount of work on the > firmware before even getting started on the software side. Even if you go > ahead and do it, the end result will be most likely very limited in its > bandwidth. "Real" logic analyzers typically use FPGA in order to achieve > high data rates. I'm using the Saleae Logic 8 at home and Logic 16 at work. > Both are highly recommended, but may or may not justify the cost, depending > on your intended usage. > > > On Thu, Feb 27, 2014 at 5:27 AM, Chiong Ching Lai > <[email protected]<javascript:> > > wrote: > >> Hi, >> >> I am planning to implement software decoder for I2C, SPI and I2S on IOIO >> OTG using DigitalIO and perhaps with PulseInput. >> Basically I have two devices (not IOIO) talking to each other using one >> of the protocol above, and use IOIO OTG to tap/probe their communication >> for both RX and TX data. Something like using IOIO OTG in place of >> oscilloscope. >> >> My concern is that SPI and I2S clock rate will be running up to around >> 3MHz. May I know what is the maximum sample rate for DigitalIO? >> Am I out of my mind? >> >> Thanks. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "ioio-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> To post to this group, send email to [email protected]<javascript:> >> . >> Visit this group at http://groups.google.com/group/ioio-users. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- You received this message because you are subscribed to the Google Groups "ioio-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/ioio-users. For more options, visit https://groups.google.com/groups/opt_out.
