MCP4131 Digital Pot Interfacing

Forum 2005-2010 (read only) Hardware Interfacing
1

So I'm getting ready to start a pretty big project which will require volume control of an analog audio circuit. Foreseeing this I ordered a couple MCP4131's from Mouser.

It's a simple SPI-controllable single channel digital pot with a maximum resistance of 75K ohms. I created a simple test circuit, just learn the ins and outs of the chip. The circuit is pretty simple, inserted the 4131 where the variable resistor would go on a LCD display brightness control.

But Chris! LCD Brightness is controlled by a 10k pot! Crap. My original idea was to add a resistor in parallel (1/10k = 1/75k + 1/R, right?). Reading up on the chip I see that it has a resistor ladder network. If I'm reading page-37 of the data sheet correctly, can't I just use this line of code to get around it -

Brightness = map(brightness, 0, 254, 0, 39);

Eehhh...or am I completely reading this wrong? Help? :o

-C

2

MCP4131 Data Sheet - http://ww1.microchip.com/downloads/en/DeviceDoc/22060a.pdf

not allowed to post links in your first post...

3

I'll give a 12k resistor a go then. Can't hook it up to the audio yet cuz payday isn't for another week! The LCD thing is just being eager and board on a Sunday afternoon...

4

Take a look at this project -> http://groups.google.com/group/rstep?pli=1 ; it has code interfacing to MCP4351, which is not too different from one you're using.