FIR
Filters for
ECG (CH2)
& Respiration (CH1)
Data Acquisition
From ADC
ADC data DRDY
Interrupt
Memory
USB
PC Application
SPI Interrupt
2 ChannelData
Reader
IIR
Filter
(DC Removal)
QRS
Algorithm
(HR) CH2
Lead Off
Status
Respiration
Rate
Algorithm
(RR) CH1
ECG signal
Respiration signal
ADS1292R DATA FLOW DIAGRAM:
PROCESSED ECG and RESPIRATION
DRDY
Interrupt
Decode PC
Commands
Lead Off Status
Lead Of
f Status
HR
1 ECG Lead
1 RESPIRA
TION CH.
Lead Of
f Status
RR
USB
SPI
-1
-1
Y(z)
1 - z
H(z) =
=
X(z)
1 - az
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Evaluation of ECG and Respiration Specific Functions
Figure 37. Live Data Stream Mode Data Flow for ADS1292R
6.2.1
Filters
IIR Filter - DC signal removal
1st Order IIR filter is used to remove the DC component from the acquired data. The following transfer
function is used for the filter:
(1)
To provide DC attenuation at 22dB, the value of alpha is chosen as 0.992. The IIR filter output is scaled
down to 16-bit and then provided to the FIR filter. The frequency response for the IIR filter is shown in
Figure 38
.
33
SLAU384A – December 2011 – Revised April 2012
ADS1x9xECG-FE Demonstration Kit
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