Could I use AD7476A IIO Single Channel Serial ADC Linux Driver also for AD7682 or exist other drivers?
The AD7476 driver only supports single channel SAR ADCs. There are no existing drivers that can support the AD7682.
The closets is probably the AD7298 IIO Multi-Channel ADC Linux Driver [Analog Devices Wiki], but the control register layout is quite different, so some adjustments are necessary if you want to use it.
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