wiered problems with 4051-mux

Using Arduino General Electronics
1

hi

ok guys this is really confusing.. I did this a couple of times, and it worked. But now I have wired a small test/debug-setup on the breadboard and somehow I can't get it working properly.

.. I have 8x button-switches connected to a 74HC4051..
.. and I have one button-switch, that is connected directly to aTeensy3.6... lets call it the "shiftButton"

void loop() {   
    pollShift(); // polls button9
    pollCtrl();  // polls buttons 1-8
}

/* Polls Shift-Button and sets Status-Var */
void pollShift() {
    if (btnShift.update()) {
        if (btnShift.fallingEdge()) {
            cfg.shiftStatus = true;
            if(cfg.debug == true) {
                Serial.println("Shift pressed..");
            }          
        } else {
            cfg.shiftStatus = false;
            if(cfg.debug == true) {
                Serial.println("Shift released..");
            }  
        }
    }
}

/* Polls all MUXES */
void pollCtrl() {
    for (int i = 0; i <= 3; i++) {    
        digitalWrite(cfg.muxPinInh, HIGH);
        cfg.MuxBit1 = bitRead(i, 0);
        cfg.MuxBit2 = bitRead(i, 1);
        cfg.MuxBit3 = bitRead(i, 2);
        digitalWrite(cfg.muxPin1, cfg.MuxBit1);
        digitalWrite(cfg.muxPin2, cfg.MuxBit2);
        digitalWrite(cfg.muxPin3, cfg.MuxBit3); 
        digitalWrite(cfg.muxPinInh, LOW); 
        delayMicroseconds(40);        
        
        pollMuxDigital(i, "btnTrackSelect", cfg.btnTrackSelectPin);          
    }
  }


/* Polls 4051 with digital Input-Sources */
void pollMuxDigital(int i, String elementName, int digitalPin) { 
    
    // btnTrackSelect
    if(elementName == "btnTrackSelect") {  
      track[i].value_btnTrackSelect = digitalRead(digitalPin);       
      if (track[i].value_btnTrackSelect == HIGH && track[i].value_btnTrackSelectOld != track[i].value_btnTrackSelect) {   
          if(cfg.shiftStatus == true) {
            if(debug == true) {
              Serial.print("# trackSelect(): "); Serial.print(i); Serial.println(); 
            }            
          } else { 
            if(debug == true) {
               Serial.print("# MuteTrack(): "); Serial.print(i); Serial.println(); 
            }            
          }
      }
      track[i].value_btnTrackSelectOld = track[i].value_btnTrackSelect;
    }

now when I only do pollShift() in the loop(), I get the correct output in the serial-monitor. but when I add the pollCtrl(), somehow the 4051 gets triggered when the shiftButton is pressed(?) oO

also the 4051 spits out that a couple of pins went HIGH, when only one button is pressed.

I really don't know what else to try/check.. the IC is defitetly wired correctly

20180913_224414.jpg
20180913_224414.jpg1700×956 659 KB

2

Please post all code, bits and pieces only obfuscate and a schematic would be a really good idea, given that you’ve got an analog multiplexer connected to pushbuttons.

I cannot tell if the inputs are wired pull up or pull down but either way, the Teensy inputs appear to be floating unless the pushbuttons are actuated.

3

It is easier to have ONE common pull up resistor on the muxer output than pull up resistors on every switch.
Leo..

4

Your code doesn't have a setup() function, often the first place to look for howlers like forgetting to
set output mode on output pins.