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:
Digital Lead Mode:
Electrode modes ( Single-ended input Electrode, Common Electrode A and Common Electrode B):
Single-ended input Electrode:
Common Electrode A:
Common Electrode B:
- 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.