I had a lot of fun with the DS1881--see this previous post--so I made another breadboard-eliminating experimenters' board for this cool digital potentiometer IC.
This second design deviated from the example found on the last page of the DS1881's data sheet: I added an on-board MCU (ATTINY1616) and exposed the IC's potentiometer pins as well as GPIO on the PCB's edge connectors.
I also uploaded the DS1881's datasheet into Claude Code then told the bot to create a CPP library for the experimenter's board, something I had never tried before. Get the code from Github, here.
Did it work?
At first--nope.
Eventually, yes.
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THE BUILD
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| Double happiness is new PCB's from this blog's patient sponsor: PCBWay! |
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| .No smoke yet.... |
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| The DS1881's I2C address is configured through hardware. If you build this project jumper or short the 0x28 or 0x29 pins to choose its I2C address. |
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| ....soldered a few components, hooked up bench power, test. If there is a short I isolated the fault to parts recently soldered. If no issues I kept building. |
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| For proofs-of-concept I am using UPDI MCU's (ATTINY generation 2 and 3) more and more often. UPDI is super easy--one wire and ground to blast firmware into the MCU--see the video here. Serial monitor isn't through USB however--for that I exposed the TX , RX and ground pins on edge connectors which got fed into a NUC Linux PC running minicom. |
CLAUDES AND SODS
Normally I would have read, re-read then re-re-read the DS1881's datasheet; over the coarse of a few days created a C library file for it. Not this time--my tech friends told me to get with the program and get AI lazy.
OK.....I used Claude Code to create a C++ .h driver file for this project:
- Installed Claude Code
- Logged in using my Claude account.
- Using browser Claude, I had it talk me through the Claude.MD file by describing what I was trying to do.
- I created the local directory for the project, CD'd into it then typed claude.
- I uploaded the DS1881 datasheet PDF into Claude.
- I didn't record the prompts I used (sorry) for the initial builds. I discovered the free tool to see previous prompts (here) but at this point I was too lazy.
The library and test sketch didn't work at first--using a DVM there was no change in resistance present the H0/W0/L0 and H1/W1/L1 pins (the DS1881's "pots" pins).
As a rheostat the DS1881 wasn't working.
I emailed Analog Devices who got right back to me--yes this should work; if I coded my firmware right, I should see resistance values of about 40K to about 4K across H0/W0 as I swept the DS1881's digital pots using the MCU.
It didn't--the DVM always showed about 30K no matter what--so I fired up my logic analyzer.
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| After years of using cheap logic analyzers I spent a small fortune upgrading to a saleae. Worth it? Yep. |
This revealed that the I2C initialization was working but after that nothing--no I2C traffic. Hello?
I reported this discovery back to Claude Code and it revised the .h file and even created an ino Arduino file for testing. Took like 5 minutes.
Uploaded the revised code and ino into the ATTINY1616 and--it worked.
WAIT! FROM THIS BLOG'S SPONSOR:
....why bother breadboarding when you can throw your ideas into Kicad, ship them off to PCBWAY and get boards back to mess around with. That's what I did here and overall a huge timesaver.
NOW WHAT, DR. SHANNON?
No photos but I breadboarded some basic circuits--voltage dividers, op amp gain, an active filter--using the exposed DS1881 pot pins. I could type on and on about this, but I'll spare all of us a lot of time--to me, there was nothing I could come up with using the DS1881 as a rheostat that was better than what I could do more efficiently with more "traditional" voltage or current controlled variable resistors like OTA's or Vactrols.
The DS1881 shines doing what it was designed to do--a simple stereo atteunator with a nice sounding log curve. Beyond that, not so sure.
I think that's where I will leave this for hitting the coda.
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| Along with my hero, Bob Widlar, Claude Shannon (the real Claude) was one of the most brilliant and colorful tech dudes of all time. Wikipedia here. |
THE CLAUDE CODA
Reviewing what Claude created: the library looked a lot more professional and succinct vs. what I would have coded by hand in C, employing extensive bitmasks, #defines than I would ever have used, and everything else C++ that drives me nuts.
I need to test each method, but haven't yet. Something about Claude Code makes me feel--lazy?
I went through the robot generated code and tried to figure out what Claude had done, really, which might be more than a lot of other programmers do these days.
The output made me realize that I suck at Boolean Algebra so I got back into claude code and had the same bot whip up a Python/UV learning tool that (hopefully) will help me master bitwise statements in C.C++ someday.
this tool was created with a single prompt--no revisions:
I need to learn bitwise operations in C and C++. This includes &, |, XOR, |=, ~= example statements like uint8_t commandByte = reg | (value & WIPER_VALUE_MASK); the learning tool should allow me to use single bytes (8 bits) and perform bitwise operations on them. Write a program in Python to help me learn the syntax of these C and C++ calls. Data entry and what is shown as the final output should entered and shown as Hex (0x04 for example) and bits (0b00001111)
The output came out way better than I expected--and does a lot more than I would have thought of.
Get the learning tool from github, here. We're cooking with oil!
I'll admit it--Claude is smarter than I am, maybe some day I will catch up a little? Nope.
See ya next time.
