[sdiy] ADc & DAC voltage dividers.. fixed or trimmer adjustables ??

Roman Sowa modular at go2.pl
Mon Feb 15 09:01:31 CET 2021



W dniu 2021-02-14 o 18:31, Mike Beauchamp pisze:
> On 2/14/21 6:59 AM, Roman Sowa wrote:
>> . Not to mention curious user turning it for fun.
> You mean circuit bending? :)
you wouldn't believe what people can do for fun with an equipment. I'm 
telling that from occasional synth-tech perspective

>
> Would it be advisable to run an auto calibration with the output fed 
> back into the input and iterate on every single bit and then store the 
> ideal DAC value into a 16bit look up table?

not if this is to be used with microcontroller having just 4k words of 
memory

> strange drop in the output that happens exactly at the halfway point - 
> so with my 14bit dac, the output is fantastic from 0-8191 and then is 
> offset below the expected voltage from 8192 to 16313.
>
> This is probably just an issue with the specific DAC i happened to 
> have, but my point is that you're going to have to test your system 
> and see what needs correcting.

aparently your DAC was R-2R ladder so it shows the biggest jump in 
midscale. Many modern DACs are resistor string, not sensitive to jumps 
of binary code where all bits flip (like from 0x3FFF to 0x4000) but also 
because such architecture their linearity is bent all over the place 
without any plan.

Roman



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