configure saradc2 reader
SAR_SAR2_CLK_DIV | clock divider |
SAR_SAR2_WAIT_ARB_CYCLE | wait arbit stable after sar_done |
SAR_SAR2_CLK_GATED | ******* Description *********** |
SAR_SAR2_SAMPLE_NUM | ******* Description *********** |
SAR_SAR2_DATA_INV | Invert SAR ADC2 data |
SAR_SAR2_INT_EN | enable saradc2 to send out interrupt |