Texas Instruments ADS1299, User Manual

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Using the Software: ADS1299 Control Registers and GUI
5.3.3 Normal Electrode Input
The Normal electrode input on the MUX routes the inputs (VINP and VINN) differentially to the internal
PGA, as
Figure 17 illustrates. An exception is if the SRB1 bit is set high. If channel is in Normal electrode
mode and SRB1 bit is set high the signal on SRB1 pin is routed to negative inputs of all channels instead
of VINN inputs.
5.3.4 MV
DD
Input and the Scope Tab
The MV
DD
input option allows the measurement of the supply voltage V
S
= (AV
DD
+ AV
SS
)/2 for channels 1,
2, 5, 6, 7, and 8; however, the supply voltage for channel 3 and 4 will be DV
DD
/4. As an example, in
bipolar supply mode, AV
DD
= 3.0V and AV
SS
= –2.5V. Therefore, with the PGA gain = 1, the output voltage
measured by the ADC will be approximately 0.25V.
5.3.5 Bias Measurement
This measurement takes the voltage at the BIASIN pin and measures it on the PGA with respect to
(AVDD + AVSS)/2 or BIASREF. This option can be used to give a calibration/test signal to ADS1299
device without connecting the calibration/test signal to the electrodes. The positive signal can be applied
to BIASIN pin and the negative input can be applied to the BIASREF pin. More details on this can be
found in
Section 7.3 .
5.3.6 Bias Positive Electrode Drive and Bias Negative Electrode
This option can be used to have a selectable bias electrode. This option routes the signal on BIASIN pin
to any of positive or negative pins of the channel inputs.
5.4 GPIO and Other Registers
The GPIO and Other Registers tab, located under the Analysis tab, includes controls for GPIO1 through
GPIO4, SRB1 control, pulse mode control and lead off comparators power down. The GPIO registers
control four general-purpose I/O pins.
Figure 23 illustrates the GPIO Control Register GUI panel.
Figure 23. GPIO Control Register GUI Panel
5.5 Lead-Off and BIAS Registers
The Lead-Off Detection and Current Control Registers and the Bias Derivation Control Registers are
located under the ADC Register
→ LOFF and BIAS tab.
23 SLAU443 – May 2012 EEG Front-End Performance Demonstration Kit
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