[sdiy] nice Digi Pot

Vladimir Pantelic vladoman at gmail.com
Tue Jun 28 00:18:20 CEST 2016


On 27.06.2016 23:48, jays at aracnet.com wrote:
> Off the top of my head the only thing that I can think of is the amount of time
> to do the operation.

that is one reason, but having to use only a few pins to control a lot of 
devices is another. if I want to control 64 of these digipots I would need 64 
chip select pins or some external logic to make some kind of 1 to 64 demuxer. 
with daisy chaining I would need only CS/CLK/MOSI and be done. add DMA pushing 
data to SPI and you even have zero CPU overhead....

> I haven't ran across any SPI or I2C devices out there that do daisy chaining and
> I've used a fair number. A lot of the FPGA chips I've had to deal with do this
> do and some of the 'smart' LEDs do daisy chaining. Are there any SPI/I2C chips
> out there that people know about?

the ADG1414 mentioned in the other thread today. I have a design where I control 
32 of them with just 4 CPU pins...





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