Improved DAC driven 3x -10 to 10V CV Generator

Howdy--this post is part III of the posts here and here. 

From last time--I created a simple control voltage generator, sourcing about 30mA with 3 independent pots, each output is -10 to +10V DC controlled by a dedicated pot.

For revision 3 I added a MCP4728 DAC and tweaked the 16-bit ADC reads, using 3 of the 4728's 4 channels, to make the CV generator's output better match the values shown in the OLED.

This simple revision had a big problem....unlike REV 1 and 2 I couldn't get the I2C bus to work--no I2C signal, anywhere.  

I figured it was a hardware issue and spent a lot of time troubleshooting based on that assumption--nope.

Then I had to move my shop--pack up every tool, every part, every file drawer, move it across town, then set it all back up again--a ton of work.

Once unpacked I took this back up in my new workshop, and Claude.ai caught the problem; the sketch used the "SSD1306AsciiWire.h" library to drive the OLED; my code was written like this:

  Wire.begin(); //set I2C 

  oled.begin(&Adafruit128x64, I2C_ADDRESS); 

  Wire.setClock(400000L);  //set I2C speed. 

meaning the I2C speed was set after constructing the oled object.

The bot told me I had to add the Wire.setClock statement before calling oled.begin. I knew that?

So--should be this.

   Wire.begin(); //set I2C 

  Wire.setClock(400000L);  //set I2C speed. 

  oled.begin(&Adafruit128x64, I2C_ADDRESS); 

(The code worked in revision 1 and 2 but not this one, making this hard to track down....)

Otherwise a simple build.

The OLED needed a standoff and I was surprised I couldn't find anything close to what I needed on the Internet so I designed and 3D printed one myself:

That sat between the front panel/Oled and the PCB:

 

Easy....

I will package all of this up (gerber, Kicad files, STL file for the standoff, Arduino code, and all the rest)--and put it on PCBWAY's community site once I am less slammed by my day job--please stay tuned--in the meantime here's the shameless plug for my sponsor.

      

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Their staff is extremely helpful and PCBWAY always turns work around quickly. 

As always--you can help this blog by checking out the PCBWAY site. Thanks.

Boring AI background.

Is that it?  Yep that's it for now. 

See ya next time.