Armbrain prototype #2: Bring it on!

on Saturday, November 1, 2014
Five months have passed from my last post about the Armbrain board. It's been a long and hard time for me. My awesome teammate who took care of signal processing and Matlab user interface left my team to pursuit her higher education abroad. Her contribution was huge. I took time to cover her role and study her code in the project. It's quite a challenge. 
I tried to turn these challenges to opportunities. I learned to use Matlab to acquire and process data. Along the way, I added some nice features to the signal acquisition function such as ring buffers and 8-channel plot. Some data structures concept in this book (Data Structures and Algorithms in C++) was implemented to reduce processing time in Matlab. The result was great! For the first time, I can plot 8+ channel from the ADS1299 chip with sampling rate at 250sample/second in realtime without dropping any package.

Now I got a solid signal acquisition, and visualization. Next step, I will test and debug the circuit signal, performance. Some initial measurement presented offsets and high noise. Let's see what will I got in the next update!  

Check out my video for this update:


4 comments:

Sixto Alc said...

Great job! I am trying to connect ADS1298 with matlab, but I hav a problem with the translation from hexadecimal to microvolts. Could you tell me please how you have done this?

Thong Vo said...

Hi Sixto,
I have difficulties to convert the data to micro volt too. I don't have nice algorithm to do it yet.
Here is the flow which you need to follow.
1) Convert the two's complement of hexadecimal of the chip to decimal
2) Then you Refer to the Data Format section in the datasheet to convert your decimal to microvolt
For example: for the ADS1299, with PGA is set to 1, every decimal step is equal to [VREF / (2^23 – 1)] .
Hope it helps.
Also, May I know more about you?

sohrab milanizadeh said...

Hi Thong .i noticed that you have used MATLAB for GUI .did you try LABVIEW too? was MATLAB GUI simpler than the others? and another favor do you have any open source data(like PCB, GUI Code ,etc) for ADS1299? Because i want to use ads1299 too for acquiring EOG .thanks dude

Thong Vo said...

Hi sohrab
I haven't used Labview for this project. You may look for openbci documents. It's a well documented open source project.

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