Limit or pullup low voltage from interrupt

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Moris526

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Hi.

Im controlling an Adafruit Neotrellis button/led board with Teensy.40

https://learn.adafruit.com/adafruit-neotrellis 2

I have a 4 x 8 boards grid soldered together.

I have an issue with the interrupt pin.

If I load only 1 board ( thou they are soldered together) it works fine. I messured the interrupt pin voltage and get

Not button pressed 3.26 v
Button pressed between 3.10 and 3.20 v and goes back to 3.26 v


If I load 32 boards and messure the interrupt pin voltage I get

Not button pressed 3.26 v
Button pressed between 2.40 and 3.13 (mostly below 2.80) and back to 3.26v


But from time to time in this case the voltage goes down to 0.80 and stays there until I press again a few time and goes back up to 3.26v

I try PULL_UP in the code with no luck...

Any Idea?
 
If I load only 1 board (thou they are soldered together) it works fine. I messured the interrupt pin voltage and get
Not button pressed 3.26 v
Button pressed between 3.10 and 3.20 v and goes back to 3.26 v

How did you measure that INT pin voltage? With an oscilloscope or digital volt meter?
I expect the INT pulse to be quite short, so a digital volt meter may not be able to catch that.

I try PULL_UP in the code with no luck...
No need for pinMode(INT_PIN, INPUT_PULLUP); as the board already has a 10K pull-up resistor mounted [R3 in the schematic].

Paul
 
How did you measure that INT pin voltage? With an oscilloscope or digital volt meter?
I expect the INT pulse to be quite short, so a digital volt meter may not be able to catch that.


No need for pinMode(INT_PIN, INPUT_PULLUP); as the board already has a 10K pull-up resistor mounted [R3 in the schematic].

Paul


Code:
void loop() {
  if (!digitalRead(INT_PIN)) {
    trellis.read();
    Serial.println("Hello");
  }




With a digital volt meter. But I got those results. When it doesnt come back up, at 0.8 it keeps printing "Hello"
 
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