It is a driver, so you can open, poll and read from /dev/iio:device0 For a quick test, do the following: After you enable the various scan_channels, start the buffer and then do the following:
dd if=/dev/iio:device0 of=~/test.txt Press ctrl-C to stop capture. Use hexdump to view the file. Regards, John > On Mar 18, 2016, at 12:37 PM, Audrey <[email protected]> wrote: > > It says: > root@beaglebone:/dev# cd iio:device0 > -bash: cd: iio:device0: Not a directory > root@beaglebone:/dev# cat iio:device0 > cat: iio:device0: Invalid argument > > > On Friday, March 18, 2016 at 3:25:13 PM UTC-4, john3909 wrote: > The buffer is available here: > > /dev/iio:device0 > > Because the driver uses interrupts, you won’t get the speed you want. The > driver has to be updated to use DMA if you want to use full speed. Reading > from the buffer will reduce your CPU load compared to using LDR_PATH because > this interface blocks until a sample is available, but not long enough for > the thread to sleep. To use DMA, IIO have introduced a DMA framework and most > of what you need is already available. However, IIO are going to be updating > the IIO DMA framework to do zero copy between the kernel module and the > socket interface, using MMU maps. > > Regards, > John > > > > >> On Mar 18, 2016, at 11:21 AM, Audrey <ao...@ <>smith.edu >> <http://smith.edu/>> wrote: >> >> Hi everyone, >> >> First of all, thank you everyone for trying to help me. I appreciate >> everyone's input. >> >> I took everyone's advice, and have moved away from bash to C++. It's >> clocking at about 2 milliseconds, but I would really like it to go down into >> the microsecond range: >> /** Simple LDR Reading Application >> * Written by Derek Molloy for the book "Exploring BeagleBone: Tools and >> * Techniques for Building with Embedded Linux" by John Wiley & Sons, 2014 >> * ISBN 9781118935125. Please see the file README.md in the repository root >> * directory for copyright and GNU GPLv3 license information. */ >> >> #include<iostream> >> #include<fstream> >> #include<string> >> #include<sstream> >> using namespace std; >> >> #define LDR_PATH "/sys/bus/iio/devices/iio:device0/in_voltage" >> >> int readAnalog(int number) >> { >> stringstream ss; >> ss << LDR_PATH << number << "_raw"; >> fstream fs; >> fs.open(ss.str().c_str(), fstream::in); >> fs >> number; >> fs.close(); >> return number; >> } >> >> int main(int argc, char* argv[]) >> { >> cout << "Starting the readLDR program" << endl; >> int value; >> int i=1; >> while (true) >> { >> float value = (float)readAnalog(0)/4095*1.8; >> cout <<"V= " << value << endl; >> cout << i << endl; >> i++; >> } >> return 0; >> } >> >> Thank you TJF for pointing me to libpruio. I'll use it later if I need it, >> but for now I rather not use the PRU if I don't need to. >> >> So I noticed this thing where I can't see the buffer, or scan_elements, or >> mode in iio:device0, and I wonder if I'm not enabling the adc dto properly >> or something: >> root@beaglebone:/sys/bus/iio/devices/iio:device0# ls -l >> total 0 >> -r--r--r-- 1 root root 4096 Mar 1 20:51 dev >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage0_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage1_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage2_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage3_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage4_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage5_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage6_raw >> -rw-r--r-- 1 root root 4096 Mar 1 22:03 in_voltage7_raw >> -r--r--r-- 1 root root 4096 Mar 1 20:51 name >> drwxr-xr-x 2 root root 0 Mar 1 20:51 power >> lrwxrwxrwx 1 root root 0 Mar 1 20:50 subsystem -> ../../../../../bus/iio >> -rw-r--r-- 1 root root 4096 Mar 1 20:50 uevent >> >> This is what I've been doing to "enable" the adc (although I don't really >> know what it is doing. I can't find the file cape-bone-iio in bbb, and if I >> try echo cape-bone-iio > test.txt, it is just a regular string.): >> echo cape-bone-iio > /sys/devices/bone_capemgr.*/slots >> >> I tried searching for /driver/iio/adc/ti_am335x_adc.c, but I can't find it >> (there's nothing in root@beaglebone:/sys/bus/iio/drivers#). Could you >> perhaps specify the full filepath? >> >> Thanks. >> >> -- >> For more options, visit http://beagleboard.org/discuss >> <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...@ <>googlegroups.com <http://googlegroups.com/>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > For more options, visit http://beagleboard.org/discuss > <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 [email protected] > <mailto:[email protected]>. > For more options, visit https://groups.google.com/d/optout > <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 [email protected]. For more options, visit https://groups.google.com/d/optout.
