tkvalentine
New member
Just throwing this out here before posting code, pictures, wiring diagrams etc.
I am building a synthesizer using:
-Teensy 4.1
-audio board version D2
-(2) SparkFun Analog/Digital MUX Breakout - CD74HC4067 daisy chained (i.e. using same common pin and channel select pins)
-(2) LEDs
-(4) momentary push buttons
Previously I built a smaller version of a synth using only the Teensy 4.1 and audio board with 12 potentiometers pinned directly to the Teensy. This worked great, no problems. I then decided I wanted more sound choice and control so redesigned the synth using 32 pots. Now I need 2 MUXs to handle all the pots.
Started by setting up and testing the double MUX daisy chain setup using the enable pin to select which MUX I wanted to read and using the advised delay between channel select and common pin read. This worked great, no issues.
I then added the MUX code to the synth audio code and wired in the MUXs ensuring not to use any of the audio board pins. The MUXs use common ground, common 3.3v, common signal pin and common channel select pins. All 32 MUX inputs are driven by 10K linear pots.
So now I check the output of the pots/MUXs and get very odd behaviour. 50% of the MUX inputs are reading correct values but show up on two channels usually 4 channels apart. For example, channel 0 reads 980 and channel 4 reads 980. 40% of the MUX inputs are not reading at all and 10% of the MUX inputs are reading the correct single channel with wildly varying values.
Obviously there is something different between my test with no audio board and the version with the audio board.
Has anybody experienced this with a similar setup? Is the audio board somehow the interfering factor?
I appreciate any insight and help that might help me resolve this head scratcher.
I am building a synthesizer using:
-Teensy 4.1
-audio board version D2
-(2) SparkFun Analog/Digital MUX Breakout - CD74HC4067 daisy chained (i.e. using same common pin and channel select pins)
-(2) LEDs
-(4) momentary push buttons
Previously I built a smaller version of a synth using only the Teensy 4.1 and audio board with 12 potentiometers pinned directly to the Teensy. This worked great, no problems. I then decided I wanted more sound choice and control so redesigned the synth using 32 pots. Now I need 2 MUXs to handle all the pots.
Started by setting up and testing the double MUX daisy chain setup using the enable pin to select which MUX I wanted to read and using the advised delay between channel select and common pin read. This worked great, no issues.
I then added the MUX code to the synth audio code and wired in the MUXs ensuring not to use any of the audio board pins. The MUXs use common ground, common 3.3v, common signal pin and common channel select pins. All 32 MUX inputs are driven by 10K linear pots.
So now I check the output of the pots/MUXs and get very odd behaviour. 50% of the MUX inputs are reading correct values but show up on two channels usually 4 channels apart. For example, channel 0 reads 980 and channel 4 reads 980. 40% of the MUX inputs are not reading at all and 10% of the MUX inputs are reading the correct single channel with wildly varying values.
Obviously there is something different between my test with no audio board and the version with the audio board.
Has anybody experienced this with a similar setup? Is the audio board somehow the interfering factor?
I appreciate any insight and help that might help me resolve this head scratcher.