[sdiy] nice Digi Pot

sleepy_dog at gmx.de sleepy_dog at gmx.de
Tue Jun 28 00:50:27 CEST 2016

For regularly updating several SPI digipots in a circular fashion, is 
not a shift register predestined for the job?
Insert one 1, clock it through 8 times and use the 8 parallel out pins 
of the register for chip select on 8 pots.
Sure, more routing space wasted...

I wonder why you would want to have *64* digi pots in "one circuit" 
controlled by one MCU, though.


Am 28.06.2016 um 00:18 schrieb Vladimir Pantelic:
> 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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