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ADS1299 broken Internal Test Signal with Arduino Pro mini

Other Parts Discussed in Thread: ADS1299

Hi. i Just Designed and finished my board (ADS1299 + ARduino Pro mini(ATmega328) ) and every thing seems fine.i can read and write the registers and i can get the correct data from noise measurement and temperature sensor and i can change the gain of the channels but when i want to set the channels for internal testing they return the positive amplitude of internal test signal and they don't toggle to negative amplitude .in other words in any case of test signal, all i get is a DC signal (but i configure the register CONFIG2 with this 0b11010000) and channels, 0b00000101....i don't know why they don't toggle and give me a square signal...every other thing is normal.BTW i am using external clock(2.048MHz) for ADS1299 and CLKSEL=0 (tied to GND). thank you for reading this question and problem.(here is a picture of what i get). the datas are in Microvolts and noise is -500uV. so i get the correct amplitude of test signal which in my case is 1.8mV. I appreciate any suggestion

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  • when i am writing DC internal test signal on CONFIG2 (0b11010011) ,it returns -2500microvolts which i think it is weird and when i double the amplitude it returns -4000 microvolts....is there any explanation?

  • Sohrab,

    That is strange. Are you certain you are converting numbers correctly from 2's complement? Perhaps you should try to input a known good signal in "normal electrode" mode and see if the result matches what you input. Otherwise just look at the binary output from the ADC and see if it matches how your code is interpreting it.

    Brian
  • Hi Brian,
    Thank you for answering my question.i tried to check if it could read correctly 2's complement and yes everything was correct.because my noise is -500 microvolts and it can read that correctly in negative form.but this is always positive side and positive number.
    I will check it with another signal just like you said.thank you again