Is there a way to convert sampled data from an Arduino into MSP audio?
Hi, I am using an Arduino to sample data (EMG data from surface electrodes to be precise). I have successfully transferred the stream to Max using the serial object, and am able to display it using the multislider object. However, I was wondering if I could convert it into an audio signal which will allow me to use all the MSP objects. I tried using sig~ but that seems to only take the first sample from every stream that gets banged out of the serial object. Does MaxMSP have the capability to convert a burst of serial packets into a uniformly sampled audio signal (essentially resampling a Max sequence of numbers into MSP audio)? Thanks.
sure, you’l have to iterate through the list at the right rate.
Depending on your settings, there will be some jitter though.
Look at the [zl] family, I think of [zl lookup]+[counter] in particular.
then go with these numbers into [sig~] one by one
Thanks, WOYTEG. I tried [zl queue] and banged out my serial data with a [metro] at my sample rate. You are right, there is some jitter, but it seems to have done the trick. I don’t seem to be able to reduce the sampling rate in MSP using the Audio Status menu (it’s 44.1 kHz and up), but this is much further than I was before your help. Thanks again.
Sorry another add-on to my question. So I performed what I described above: I routed [serial] which bursts out 1 kHz samples into [zl queue] and banged out the queue every 1 ms using [metro]. The output of [zl queue] is routed to [sig~].
Here’s something I observed though, when I hooked up [sig~] to [capture~], I notice that values in capture change every 64 samples. This probably has to do with my Signal Vector Size set at 64. But my samples are coming in at 1 kHz, being resampled at 44.1 kHz by [sig~], so I should get a new value in [capture~] roughly every 44 samples, not 64. This is where I think it’s skipping some samples. Any thoughts on this?
Also, I was wondering if instead of repeating 64 (or hopefully 44) samples, there’s any way to interpolate between samples. I tried to use [line~] but that didn’t seem to work. The problem is repeating the samples ends up affecting the signal in the frequency domain, creating harmonic distortion.
If you have an ideas for a solution, I’d really appreciate it. I’ve literally been beating my head over this for hours.
Hard to say without seeing the patch. Try changing your vector size to make sure it has anything to do with it, as I’d doubt it.
Try interpolating using [slide~] or a custom lowpass.(filterdesign)
If you wish for a low sampling rate use poly~.