AD5940 BIOZ-2Wire Configure Switch matrix / AN-1557

Following the 2-Wire Bioimpedance Block Diagram in AN-1557, I found that the correct T-switch and N-switch settings should be:
pBIOZCfg->NswitchSel = SWN_AIN1;
pBIOZCfg->TswitchSel = SWT_AIN1 | SWT_TRTIA;

But the configure switch matrix in AD5940_BIOZ-2Wire application at latest commit 08c23316 on the master brand is different:
pBIOZCfg->NswitchSel = SWN_AIN2;
pBIOZCfg->TswitchSel = SWN_AIN2 | SWT_TRTIA;

The change resulted in the output of the BIOZ-2Wire application at this commit that was different from the output in the application note (AN-1557) in section 2-WIRE BIOIMPEDANCE.

Could you clarify this issue?


  • +1
    •  Analog Employees 
    on Aug 31, 2021 12:02 PM


    In the Bioz_2_wire application,

    AIN2 is mentioned in the heading (as these are the pins used in most examples)

    * @note This example is modified from BIOZ example. This one is for 2-wire impedance measuremnt.
    * The default pins used are CE0 and AIN2. The differnce with BIOZ is that the body voltage
    * Measurment is replaced with excitation voltage measurment and it's only measured once.

    If AIN1 is needed to be retained,

    change need to be done only here in the whole code:

    pBIOZCfg->NswitchSel = SWN_AIN1;
    pBIOZCfg->TswitchSel = SWN_AIN1;