Question
I am using the AD5235 Digital Potentiometer in my Final Year Project at
University. I am going to try and daisy chain several of the Potentiometers
together, but I am unsure where to begin. Do you have any technical notes on
Daisy-chaining your digital potentiometers?
Answer
To daisy chain multiple AD523X devices, simply connect SDO to SDI and run a
common SCLK and /CS to all devices. To program many AD5235s in a "daisy chain"
configuration. Pull the /CS lines low on all chips. Send the data into the CLK
and SDI pins of the first AD523X in the chain. The data format should be data
for the last potentiometer in the chain sent first. Once data for all
converters in the chain is sent, a positive edge on /CS will load data into all
potentiometers simultaneously.
You must always write the same word length to the chain of devices. For example
when two AD5235s are daisy chained together, you must always write 32 bits, for
4 devices, you must write 64 bits. If you only want to update the contents of a
single device, simply write a NOP to the device locations you do not wish to
update.
Also ensure that the recommended 2k pullup resistor is used on SDO.