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STM32 Blue Pill ADC Values Too Low in PlatformIO

 

I kept getting values that were way too low when feeding an ADC on the STM32 Blue Pill 3.3V. I should have been getting values that were around 4000 and instead I was closer to 800.

Solution
1) The default ADC in the Arduino library is set to 10-bit resolution. This is what you normally get with analogRead(). To change it, put this in your setup(). Read more about it here: https://www.arduino.cc/reference/en/language/functions/zero-due-mkr-family/analogreadresolution/

analogReadResolution(12);

Notes
— This would have been a much easier problem to solve if i had been getting values of around 1000. It turns out that my ADC pin wasn’t getting exactly 3.3V. There was a voltage drop in my system – I’ve got a huge mess currently hooked to the Blue Pill – that knocked it down to around 3V. Normally, calculating bit resolution in decimal is 2^x – 1. So 2^10 – 1 = 1023.

— PlatformIO had nothing to do with the error. I’m new to PlatformIO and never know if my issues are due to the STM32’s specific needs, the Arduino library, or some kind of PlatformIO specific issue. It seems that as long as the hardware is setup correctly and
#include <Arduino.h>
is at the top of the program/sketch/whatever, PlatformIO has no ill effects. The problems I have had aren’t the fault of PlatformIO but from adapting libraries intended for AVR to STM32F1.

 

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Use Python To List All Files In A Directory

I needed a lengthy list of files for a massive 3D printing project I’m starting and I didn’t want to have to copy and paste each file one at a time.  Brandon’s Rule #232:  If you are faced with a 2 minute task that bores the hell out of you, invest 15 minutes into automating it.

Everyone should have Sublime Text installed on their machine and have just enough competence in Python to Google the living crap out of any problem that arises.

This Python code simply lists all the files in the directory containing this file.


from os import listdir
from os.path import isfile, join

mypath = '.'
onlyfiles = [f for f in listdir(mypath) if isfile(join(mypath, f))]

for x in range(len(onlyfiles)):
print(onlyfiles[x])
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Add 32 Buttons With Just 2 Pins With MCP23017 Expander

I need about 40 buttons for my synth project.  I’m trying to run the entire synth with a single STM32 Blue Pill.  I’ve already shown how I can run 256 LEDs with 3 pins LINK IT HERE.  Since the MCP23017 is I2C, I could possibly run 128 buttons on 2 pins.  For now, I’m just running two of my Tactile Switch Female Dog boards (each with 16 buttons and a MCP23017 chip).

Stuff I Didn’t Know Yesterday About The MCP23017 Expander

  • I needed to power cycle this chip quite a bit when it didn’t act as expected.  If you start to lose your mind, go ahead and lose it.  Then kill the power for a second.
  • When using the internal pullups, we are in active low land.  Pushing the button gives a zero.  That’s normal.  I got confused when using the onboard STM32 Blue Pill LED as the stupid thing is also active low.  Apparently, I can handle only one active low thing per week.

I debated whether I wanted to use a library or just bang it out with Wire commands.  It’s really all the same, but I guess the library saves 2 seconds of work (at what cost?).  I opted for the Adafruit MCP23017 library, but I’m keeping a link close by for the tutorial using Wire so I don’t have to think or open a datasheet today.

Code For A Single MCP23017 Expander

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_MCP23017.h>
 
#define ONBOARD_LED PC13
 
// Connect pin #12 of the expander to PB6  I2C clock
// Connect pin #13 of the expander to PB7  I2C data
 
Adafruit_MCP23017 mcp;
 
void setup()
{
    // The address is specified using the A0, A1, and A2 pins
    mcp.begin(); // use default address 0, otherwise, the address needs to be defined
 
    for (int i = 0; i < 16; i++)
    {
        mcp.pinMode(i, INPUT); // MCP23017 pins are set for inputs
        mcp.pullUp(i, HIGH);   // turn on a 100K pullup internally
        delay(10);
    }
    pinMode(ONBOARD_LED, OUTPUT); // use the c13 LED as debugging
 
    // Sanity check to confirm functionality with onboard LED
    for (int i = 0; i < 8; i++)
    {
        digitalWrite(ONBOARD_LED, HIGH);
        delay(100);
        digitalWrite(ONBOARD_LED, LOW);
        delay(100);
    }
}
 
void loop()
{
 
    // Check for a button press of any button.  A LOW indicates a button press
    if (mcp.digitalRead(0) == 0 ||
        mcp.digitalRead(1) == 0 ||
        mcp.digitalRead(2) == 0 ||
        mcp.digitalRead(3) == 0 ||
        mcp.digitalRead(4) == 0 ||
        mcp.digitalRead(5) == 0 ||
        mcp.digitalRead(6) == 0 ||
        mcp.digitalRead(7) == 0 ||
        mcp.digitalRead(8) == 0 ||
        mcp.digitalRead(9) == 0 ||
        mcp.digitalRead(10) == 0 ||
        mcp.digitalRead(11) == 0 ||
        mcp.digitalRead(12) == 0 ||
        mcp.digitalRead(13) == 0 ||
        mcp.digitalRead(14) == 0 ||
        mcp.digitalRead(15) == 0)
    {
        digitalWrite(ONBOARD_LED, LOW); // Turn on the dumb, active low PC13 onboard LED
        delay(1000);                    // Keep the LED on a second.
    }
    else
    {
        digitalWrite(ONBOARD_LED, HIGH); // Turn off the dumb, active low PC13 onboard LED
    }
}

Code For 2 Simultaneous MCP23017 Expanders (32 Buttons)

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_MCP23017.h> 

#define ONBOARD_LED PC13

/********** HARDWARE *****************/
// Connect pin #12 of the expander to PB6  I2C clock
// Connect pin #13 of the expander to PB7  I2C data
// Remember that I2C requires pullups on clock and data pins.
// I used 2.2k resistors because I mindlessly read it on the internet
// From a guy who typed wth confidence

/********** NOTES ********************/
// If the board acts stupid and you don't want to blame yourself,
// power cycle your microcontroller and the MCP23017

Adafruit_MCP23017 mcp1; // Create an object for the first board.
Adafruit_MCP23017 mcp2; // Create an object for the second board.

void setup()
{
    // The address is specified using the A0, A1, and A2 pins
    mcp1.begin();    // use default address 0, otherwise, the address needs to be defined
    mcp2.begin(001); // make sure to give A0 5V.

    for (int i = 0; i < 16; i++)
    {
        mcp1.pinMode(i, INPUT); // MCP23017 #1 pins are set for inputs
        mcp1.pullUp(i, HIGH);   // turn on a 100K pullup internally
        mcp2.pinMode(i, INPUT); // MCP23017 #2 pins are set for inputs
        mcp2.pullUp(i, HIGH);   // turn on a 100K pullup internally
    }
    pinMode(ONBOARD_LED, OUTPUT); // use the c13 LED as debugging

    // Sanity check to confirm functionality with onboard LED
    for (int i = 0; i < 8; i++)
    {
        digitalWrite(ONBOARD_LED, HIGH);
        delay(75);
        digitalWrite(ONBOARD_LED, LOW);
        delay(75);
    }
}

void loop()
{

    // Check for a button press of any button.  A LOW indicates a button press
    // There is surely a smarter way to do this, but that never stopped me.
    if (mcp1.digitalRead(0) == 0 ||
        mcp1.digitalRead(1) == 0 ||
        mcp1.digitalRead(2) == 0 ||
        mcp1.digitalRead(3) == 0 ||
        mcp1.digitalRead(4) == 0 ||
        mcp1.digitalRead(5) == 0 ||
        mcp1.digitalRead(6) == 0 ||
        mcp1.digitalRead(7) == 0 ||
        mcp1.digitalRead(8) == 0 ||
        mcp1.digitalRead(9) == 0 ||
        mcp1.digitalRead(10) == 0 ||
        mcp1.digitalRead(11) == 0 ||
        mcp1.digitalRead(12) == 0 ||
        mcp1.digitalRead(13) == 0 ||
        mcp1.digitalRead(14) == 0 ||
        mcp1.digitalRead(15) == 0 ||
        mcp2.digitalRead(0) == 0 ||
        mcp2.digitalRead(1) == 0 ||
        mcp2.digitalRead(2) == 0 ||
        mcp2.digitalRead(3) == 0 ||
        mcp2.digitalRead(4) == 0 ||
        mcp2.digitalRead(5) == 0 ||
        mcp2.digitalRead(6) == 0 ||
        mcp2.digitalRead(7) == 0 ||
        mcp2.digitalRead(8) == 0 ||
        mcp2.digitalRead(9) == 0 ||
        mcp2.digitalRead(10) == 0 ||
        mcp2.digitalRead(11) == 0 ||
        mcp2.digitalRead(12) == 0 ||
        mcp2.digitalRead(13) == 0 ||
        mcp2.digitalRead(14) == 0 ||
        mcp2.digitalRead(15) == 0

    )
    {
        digitalWrite(ONBOARD_LED, LOW); // Turn on the dumb, active low PC13 onboard LED
        delay(1000);                    // Keep the LED on a second.
    }
    else
    {
        digitalWrite(ONBOARD_LED, HIGH); // Turn off the dumb, active low PC13 onboard LED
    }
}

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Is there evil in the world? Yes! LabVIEW!

My boss – okay he’s a professor at school – at my internship – okay, it’s an unsanctioned internship and I’m working for free – asked me to clean up the GUI on a LabVIEW power measurement circuit. I have vast experience with .css from my html background so I thought “no problem”.

I’ve debated if evil truly exists beyond the realm of the mentally ill. Evil acts certainly occur. Is Jeffrey Dahmer evil or just crazy? Maybe this crazy vs evil thing is a semantic mess, but we treat evil much differently than we treat insanity in American culture.

Now I have my answer. I can say definitively, 100%, without a doubt that evil exists in the world and I can only assume that the creators of LabVIEW over at National Instruments are not mentally ill. It would take too many people all with the same scheming hands and maniacal laugh to be working in unison to create a tool that has created so much wrong in the world.

How many hours do I need to invest in adjusting the size of font? Should it take hours and hours to change the background color? Why can’t I just select the good ol’ color codes from the html world or the Photoshop world? Why is it when I save a file, I’m asked all these nonsensical questions when the current paradigm of saving files is well-understood and works incredibly well. Why is it the movement resolution of a label is high when three inches from the gauge, but heavily quantized when close to the target.
WHY CAN’T I ZOOM??????

There isn’t a single facet of the LabVIEW software that doesn’t take 10x longer than it should to learn. At the end of the day, the hardware behind LabVIEW is so ridiculously high priced that I can’t think of an instance where the graphical software makes a bit of sense to implement. Because LabVIEW will waste hours and hours on things that Microsoft Paint mastered in 1991, the overall project time isn’t all that different from what one may expect when programming in C.

LabVIEW is evil. Case closed.

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A Usable Dark Theme in Eclipse in 10 Seconds

I just spent about 3 hours getting lost in the bottomless toilet that is the Eclipse Preferences menu. For those who are out of the loop, dark themes are like running water and refrigeration. There is no going back to old ways without them. I’d consider ditching the fridge before giving up dark themes. Many IDEs make this easy on you. Sublime Text comes this way. Notepad++ can get you there in 3 seconds. Eclipse has been a disaster. The reason is that Eclipse has their colors busted into an untold number of menus and they seem to look at the theme of the code differently than the theme of their GUI.

Solution
Help > Eclipse Marketplace > Search for “Darkest Dark Theme with DevStyle”

Install it. Do whatever it says. Done

This should have been a default feature in Eclipse. It would have saved me about three hours of horror.

Brandon