Thanks for the suggestions; The issue is that these sensor may need to communicate with the board at the same time; imagine a sort of mocap device for a quadruped: if they walk, they are in fact using all 4 legs at the same time, so I need a way to capture these values at the same time. From what I understand, if I use an ADC, I am forced to tell it to switch to a specific input, so it works more like a radio selector (multiple station, but you can get only one at time), than a electric strip (many plugs can take electricity independently at the same time).
The solution that you mentioned (the one with the device that send all the data at once), seems functional to my case. I don't need instantaneous reactivity by the device, since it is more used to capture data on movements, convert it to something that the main computer can digest (done on the BBB), and then sent to the computer, that will grab the data and apply it to a mesh. Each of these steps will take time, so I am aiming at something usable with a small lag; that's why Analog seem the quickest way to get the data out. I am basically clueless about what could I potentially buy, to achieve what I want; and can't really find any reference online...if there is one is either well hidden or people don't like to talk about it. On Thursday, February 13, 2014 6:37:37 PM UTC-8, Guy Grotke wrote: > > If your requirements are pretty relaxed (like running a touch screen), > then you could use four GPIO outputs as address inputs for a 16-to-1 analog > MUX chip. Your program would select the input you want to measure (of 16 > possible), which would connect that input to an ADC pin. > > If you really need 10 perfectly synchronized samples, then I suggest you > build a board with 10 individual ADCs all connected to one common “sample & > convert” signal. The Beaglebone can drive that signal using one GPIO > output, wait for the maximum A-to-D conversion time, and then read all of > the ADCs using an SPI or I2C chain. (Each ADC output connected to the next > ADC input.) > > Of course, if you need those samples to be perfectly periodic (like for an > FFT), then you will have to drive that “sample & convert” output using one > of the PRUs or a hardware timer. There is too much going on in a Linux > system to make anything happen in software at a precise time. The sampling > jitter would be many milliseconds, and still too large for any kind of > signal processing even with the realtime patches in the kernel. This is > the kind of application TI had in mind when they included the PRUs: Each > is a 200 MHz processor with 5 nsec instructions and no interrupts or tasks > to make their responses non-deterministic. They are yours to command, and > they can talk directly to all the hardware registers without needing > drivers, kernel execution state, virtual addresses, etc. > > > *Sent:* Thursday, February 13, 2014 5:16 PM > > *Subject:* Re: [beagleboard] can I use any of the GPIO of the Beaglebone, > for analog reading? > > This patch is for ADC touch screen , generally resistive touch screen > will have 4 lines for ADC X+ X- Y+ Y- > > so , this will cost 2 ADC > > for my understand , this round robin is just between this 2 ADC , instead > of two sensors in one ADC converter. > > From top thread , if you want to use over 10 sensors for ADC , you need > external ADC chip . and do some communication work with am3358 > > If you want to have some flexable and no much than 10 sensors , > > what about add a stm32 ? > > > > >> >> On Wednesday, February 12, 2014 8:42:27 PM UTC-5, Karl Longen wrote: >>> >>> DOH >>> >>> You make a good point...I thought that the GPIO were configurable >>> between analog and digital. >>> >>> as ADC I've found this: not sure if it is right for me thou. I need >>> these sensors to shoot data concurrently, while I think this board, allow >>> only one signal at time, unless you switch input >>> >> >> The system is capable of reading the ADC inputs rapidly in round-robin >> fashion. It depends on having kernel support for this. The changes went >> into the mainline kernel last fall: >> http://beagleboard-gsoc13.blogspot.com/ >> >> -- >> 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 mailto:beagleboard%[email protected] <javascript:>. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- > 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] <javascript:>. > For more options, visit https://groups.google.com/groups/opt_out. > -- 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/groups/opt_out.
