ES_SMPREG_VOL_ADC
es1371_src_write(es, ES_SMPREG_VOL_ADC, 1 << 12);
es1371_src_write(es, ES_SMPREG_VOL_ADC + 1, 1 << 12);
es1371_src_write(es, ES_SMPREG_VOL_ADC, n << 8);
es1371_src_write(es, ES_SMPREG_VOL_ADC + 1, n << 8);