Hi Roberto,
Sure...
The "RDATAC" mode puts the ADS1259 in a state where it only expects incoming SCLKs for the purpose of clocking out data. It is convenient when you want continuously sample and convert you input signal because you don't need to send any additional commands before clocking out the data.
However, to perform other operations - such as reading or writing to the ADC registers - you need to make sure to exit the "RDATAC" mode by sending the SDATAC command.
It sounds like you do not need to continuously sample and convert your input signal; therefore, you may want set the PULSE bit in the CONFIG2 register to "1" so that the ADS1259 only performs a conversion when you, A) toggle the START pin, or B) send the START command.
Therefore, your order of operations would look like:
- Power up
- Send SDATAC command
- Write to all the device registers you wish to change (from the default value)
- Read back all of the registers to confirm the settings and operation modes are correct.
- Send a START condition (SPI command or toggle GPIO connected to ADS1259 START pin)
- Note the SPI timing on pg 6 or the GPIO pulse timing on pg 23 (of the ADS1259 datasheet)
- Wait for /DRDY to go low
- Send the RDATA command followed by additional SCLK's to clock out the data (and checksum if configured).
- Repeat steps 5-8 or (OPTIONAL) if you don't expect to request more data soon you can power down the device, but will need to allow time to reconfigure the device registers - they don't retain their values while powered down - in which case repeat steps 1-8.
Another thing to consider is calibration. You may only calibrate your system once and never again, or you may re-calibrate it regularly. Offset calibration is simple to perform anywhere; however, gain calibration requires that you provide a known accurate full-scale signal - this is sometimes difficult out in the "field" or where ever you operate your system in it's final application. You would probably insert the calibration routine between steps 4 & 5, and read back the registers again (to make sure your calibration coefficients look reasonable) then proceed to step 5.
Best Regards,
Chris