I am using a PIC24 microcontroller and have multiple inputs. Via these I would like to obtain analog voltage data as fast as possible. I have 8 different data arriving to the microcontroller and I am a bit confused how to solve the problem.
My first idea was to to read in the data sequentially. First from AN0, then AN1 and so forth, but this may take quite a while and I am not at all sure it would be fast enough to do without any other trick. Especially because I do not only want to read in one single value per pin, but an array of voltages, then store and numerically integrate and send the results through USB to the PC. While doing so, new data should be constantly received via the aforementioned pins.
Is it feasible at all what I'm trying to achieve here?
Thanks in advance :)
You should think through your requirements a little more, especially the "at the same time" and "as fast as possible" statements. If you sample each channel within 10 to 100 microseconds of the next would that be satisfactory? What is the maximum frequency of the input signal that you need to detect? Your sampling frequency should be at least double the maximum signal frequency of interest.
Use a single ADC with enough input channels. Configure the ADC so that each time it is triggered to take a sample it will sample all of the channels in sequence (multichannel scan). It won't sample all 8 channels at literally "the same time", but it will cycle through each channel and sample them one after the other at nearly the same time. This could be within a few microseconds depending on the clock rate of the ADC and the channel setup time that you configure.
Now you could configure the ADC to sample in continuous mode where it would start the next sample scan immediately after finishing the previous scan. That would be "as fast as possible" but that might be faster than you need and produce more data than can be processed. Instead you should choose the sampling rate based upon the input signal frequency of interest and setup the ADC to sample at that rate. This rate might be much less than "as fast as possible". You might configure the ADC to collect one sample per channel when it is triggered (single conversion mode) and also setup a hardware timer to expire at the desired sampling rate and trigger the ADC to take a sample scan. The sample period (time between samples) must be greater than the time required to scan all the channels because you won't be able to trigger the ADC again before it has completed the previous channel scan.
If you really need to sample all channels at literally the same time then you probably need a separate ADC for each channel and then trigger all the ADCs to collect a sample at once.