Using TI's expansion chip, model: PCA9534ARGTR
schematic diagram:
Problem phenomenon:
1. The software cannot read the device through IIC;
2. In the schematic diagram above, before the IIC inlet of R18 R19 (remove the resistance), measure the IIC waveform and confirm it;
However, with the addition of R18 and R19 (after the expansion chip is connected), the IIC waveform is abnormal and the device cannot be read;