ADAS1000 - Converting ECG raw data to voltage

Document created by Padraic Employee on Mar 6, 2014
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Q: I am able to read raw data for my leads/electrodes, how do I convert this raw data to an ECG voltage?

 

  • Firstly decide the operating mode. Here are 3 main operating modes on the ADAS1000: Analog Lead Mode, Digital Lead Mode and Electrode Modes. There are 3 Electrode Mode Configurations available depending on the application requirements.

          Analog Lead Mode:

Analog Lead mode.png

          Digital Lead Mode:

Digital Lead mode.png

          Electrode modes ( Single-ended input Electrode, Common Electrode A and Common Electrode B):

                   Single-ended input Electrode:

Single Ended input Electrode mode A.png

                     Common Electrode A:

Common Electrode mode A.png

                    Common Electrode B:

Common Electrode mode B.png

 

  • Write to the relevant bits in the FRMCTL, ECGCTL and CMREFCTL registers as described in the ADAS1000 datasheet to configure the mode.
  • Write to the FRAMES register.This issues the read command to start putting the converted data out on the SDO pin.

 

A:

  • The received data will be left justified (MSB) irrespective of data rate.
  • In electrode mode and analog lead mode, the digital result value is an unsigned integer.
  • Electrode mode and Analog Lead Mode:

          Minimum value (000…) = 0 V

          Maximum value (1111….) = VREF/GAIN

                   LSB = (2 × VREF/GAIN)/(2N– 1)

                    ECG (voltage) = ECG Data × (2 × VREF/GAIN)/(2N– 1)

  where N = number of data bits: 16 for 128 kHz data rate or 24 for 2 kHz/16 kHz data rate.

 

  • In digital lead/ mode, the value is a signed twos complement integer format and has a 2× range compared to electrode format because it can swing from +VREF to –VREF; therefore, the LSB size is doubled.
  • Digital lead mode:

          Minimum value (1000…) = −(VREF/GAIN)
           Maximum value (0111….) = +VREF/GAIN

                    LSB = (4 × VREF/GAIN)/(2N – 1)
                    ECG (voltage) = ECG Data × (4 × VREF/GAIN)/(2N – 1)

  where N = number of data bits: 16 for 128 kHz data rate or 24 for 2 kHz/16 kHz data rate.

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