I have problems with Arduino AD8232 sensor. I use classic Arduino 1.8.2 for Arduino and Processing for visual processing of the data. According to the graph Arduino sends data in at least 100-300Hz range (graph between two R peaks (cca1 sec) is pretty precise), but when I export raw data I get a value for every approx. 17 miliseconds (around 60 Hz). I don't see why I can't get more precise raw data since more precise raw data is clearly used for the graph estimation. Are there any hardware or software obstacles I am not aware of?
Thanks!
I had similar problem with processing of row ultrasound signal.
The way is to use SD card to store data from sensor then to transfer to PC
next solution was to increase the the speed of ADC of the analog input
prescaler 4 * 13 * 1/16E6 = 0.00000325 ( 3.25 µS)
ADCSRA &= ~(bit (ADPS0) | bit (ADPS1) | bit (ADPS2)); // clear //prescaler bits
ADCSRA |= bit (ADPS1); // 4
but if the speed is too high there will be high error rate too
everything have to be balanced
I agree with @Zaltin. Adding more, when you said you are exporting raw data, are you trying to read simultaneously as well?
When export of raw data happens, then at that point reading from ADC will not happen as the execution is sequential from HW point of view. So try using a timer to schedule tasks or as Zaltin said write to an SD card or to file and then export the entire file after a duration of time.
Another option is, you can even dump the data as it comes to a cloud like azure or thingspeak and then either do the analysis on the cloud if you want it real-time or later transfer the data to your local host i.e. the PC.
Hi Jan,
Have a look on my paper: "BITalino: A Novel Hardware Framework for Physiological Computing". I have described a firmware workflow for the acquisition of physiological signals using the ATmega328P microcontroller which is the MCU within standard Arduino Uno and Mini, etc. That firmware workflow ensures accurate sampling rates and also by streaming data via Bluetooth it may decrease the impact of the 50/60Hz noise and harmonics from the power lead into your acquisition system.
Best,
Jose
Thanks everybody,
your suggestions are really helpful. For now I have successfully increased the data acquisition precision by bypassing analysis and using serial port terminal apps such as puTTy and CoolTerm to capture data and analyze it later.
:)
Best,
Jan
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