Q: How to configure multiple ADXXXX DACs in daisy chain mode?
A: A figure on the data sheet shows how to connect multiple devices in daisy chain mode. The SDO of the first device on the chain is connected to the SDI of the next device until the SDO of the last device of the chain is connected back to the microcontroller/DSP. The AD5686R data sheet have an example diagram on how to connect devices in daisy chain.
Q: I already have connected the DACs as specified on the data sheet but I still am not able to configure or write to the devices. What seems to be the issue?
A: Some DACs cannot be used directly in daisy chain configuration. A daisy chain enable command (DCEN) needs to be issued to all of the devices to be able to communicate with them in a chain. Consult the Serial Interface section of the data sheet for more details.
An example device wherein the a DCEN bit needs to be set is the AD5686R to enable the daisy chain.. The daisy-chain mode is enabled by setting Bit DB0 in the DCEN register. The default setting is standalone mode, where DB0 = 0. Refer to Table 8 & Table 10 on how to set the control register for the AD5686R in daisy chain.
Q: How do you perform a readback of the registers on the DAC configured in daisy chain?
A: For example you have 3 DACs configured which needs a 24-bit sequence each and are already able to do the write sequence in daisy chain and you want to read the 2nd DAC in the chain.
The readback of the 2nd DAC will be on the 2nd 24-bits from the output the 3rd DAC.