Trellis ghost LED

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lunes
 
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Joined: Sun Aug 31, 2014 2:34 am

Trellis ghost LED

Post by lunes »

Several weeks ago I bought 4 Trellis PCBs for my monome-style MIDI controller. After *lots* of hours tinkering with it I got everything working (almost) the way I imagined it.
my MIDI controller (currently with one Trellis removed for debugging)
my MIDI controller (currently with one Trellis removed for debugging)
sugarcube.JPG (113.72 KiB) Viewed 379 times
Yesterday while testing the software part, I experienced a really annoying glitch: in certain circumstances a LED starts to glow (rather dimmed) although I did never tell my Trellis to do so. I narrowed it down to this sketch:

Code: Select all

#include <Wire.h>
#include "Adafruit_Trellis.h"

Adafruit_Trellis matrix0    = Adafruit_Trellis();
Adafruit_Trellis matrix1    = Adafruit_Trellis();
Adafruit_Trellis matrix2    = Adafruit_Trellis();
Adafruit_Trellis matrix3    = Adafruit_Trellis();
Adafruit_TrellisSet trellis = Adafruit_TrellisSet(&matrix0, &matrix1, &matrix2, &matrix3);

void setup() {
  trellis.begin(0x70, 0x71, 0x72, 0x73);
  trellis.clear();

  for (byte i = 0; i < 4; ++i) {
    trellis.setLED(0 + i * 16);
    trellis.setLED(1 + i * 16);
    trellis.setLED(7 + i * 16);
  }
}

void loop() {
  trellis.readSwitches();
  trellis.writeDisplay();
  delay(30);
}
After uploading this sketch to my Arduino it looks like that:
no key pressed
no key pressed
no-key.JPG (86.1 KiB) Viewed 379 times
When I press button 8 (while LED 8 is on) everything is still OK:
only key 8 pressed
only key 8 pressed
key8.JPG (50.67 KiB) Viewed 379 times

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lunes
 
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Joined: Sun Aug 31, 2014 2:34 am

Re: Trellis ghost LED

Post by lunes »

But when I press button 1 or 2 (while LED 1 or LED 2 is on) LED 4 starts to glow dimly:
key1and8.JPG
key1and8.JPG (56.68 KiB) Viewed 378 times
key2and8.JPG
key2and8.JPG (47.91 KiB) Viewed 378 times
So this only happens, when:

- LEDs (1 or 2) and LED 8 are switched on
- I press button (1 or 2) and button 8.

It does not matter on which of my 4 Trellises I test this. It is always the same. It even does not matter, if there are 4 Trellises in the TrellisSet or if I test it with just a single Trellis.

I tried the sketch with an Arduino Duemilanove and with a Arduino Pro Mini 5V but this does not change anything.

After all the (great!) hours of work I am _so_ upset. Could anyone please try to replicate my problem? What am I doing wrong? Or is there a real problem with my 4 Trellis PCBs?

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pburgess
 
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Joined: Sun Oct 26, 2008 2:29 am

Re: Trellis ghost LED

Post by pburgess »

I've been able to reproduce the issue here. Not certain yet of the cause...I'll need to escalate this to the designer.

Might be an oversight in the PCB design. Might be a limitation of the matrix & LED driver chip. Doesn't seem to be software-related, since it occurs even when the code stops polling or refreshing the matrix.

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lunes
 
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Re: Trellis ghost LED

Post by lunes »

Thanks for your reply! That's somehow relieving.

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adafruit2
 
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Joined: Fri Mar 11, 2005 7:36 pm

Re: Trellis ghost LED

Post by adafruit2 »

yeah this is some scanning side effect. its nothing 'damaging', just life in the LED/button matrix-scanning world :)

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lunes
 
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Re: Trellis ghost LED

Post by lunes »

pburgess wrote: Might be an oversight in the PCB design. Might be a limitation of the matrix & LED driver chip. Doesn't seem to be software-related, since it occurs even when the code stops polling or refreshing the matrix.
Any news about this?

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pburgess
 
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Re: Trellis ghost LED

Post by pburgess »

Limor looked over the PCB, it seems to check out. Near as we can tell, it's just a quirk of the design, something at the silicon level that we can't work around.

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