Errata in BLE Sense Rev 2 Tutorial RGB Pixel Control

Official Hardware Nano Family Nano 33 BLE Sense
1

This tutorial has an error in RGB pixel control:
docs.arduino.cc/tutorials/nano-33-ble-sense-rev2/cheat-sheet

The tutorial has:
image

But this code running on my BLE Sense Rev 2 shows that logic LOW turns ON the LED pixels.

void setup() {
  // no setup required
}

void loop() {
  // turn all LED pixels ON
  digitalWrite(LEDR, LOW); //RED
  digitalWrite(LEDG, LOW); //GREEN
  digitalWrite(LEDB, LOW); //BLUE
  while(1);
}

Also, while not an errata, when using analogWrite, a 255 value turns a pixel OFF and a 0 value turns a pixel ON. Not an error in the tutorial, just counter-intuitive.

image

2

You should define the pin to which each color of the RGB LED is connected...

#define LEDRpin 2
#define LEDGpin 3
#define LEDBpin 4

Then declare each pin as OUTPUT...

  pinMode(LEDRpin, OUTPUT);
  pinMode(LEDGpin, OUTPUT);
  pinMode(LEDBpin, OUTPUT);

So, in your code, try this... if LOW does not enable your RGBLED, try HIGH... it will depend on the RGBLED common leg.

#define LEDRpin 2
#define LEDGpin 3
#define LEDBpin 4

void setup() {
  pinMode(LEDRpin, OUTPUT);
  pinMode(LEDGpin, OUTPUT);
  pinMode(LEDBpin, OUTPUT);
}

void loop() {
  // turn all LED pixels ON
  digitalWrite(LEDR, LOW); //RED
  digitalWrite(LEDG, LOW); //GREEN
  digitalWrite(LEDB, LOW); //BLUE
  while(1);
}
3

That is nothing to do with the code and everything to do with how your LEDs are wired up.

So shows us a schematic of what you have and maybe we could tell you where you are misunderstanding things.

4

Thanks for the quick response. Your code performs the same as mine in turning all 3 pixels on.

My point in posting this is that the tutorial is in error in stating the that digitalWrite(LEDR, HIGH); turns the LED pixel on. Rather it is digitalWrite(LEDR, LOW); which turns the pixel on. The logic is inverted relative to the text.

5

The schematic is the standard, unaltered, BLE Sense Rev 2 board. The LED pixels are on the board. The tutorial is for the BLE Sense Rev 2 board. The point in posting is that the tutorial has a logic error.

I expected the posted code snippet in the tutorial for the BLE Sense Rev 2 board to work as stated. I did not expect the logic error. Hence I was sharing this observation.

6

And I expected you to cooperate by actually supplying the schematic, not what you answered.

7

My apologies. I will have to go find the BLE Sense Rev 2 schematic on line.

8

Yes... noted in my comment above...

9

Please, my objective here is to communicate what I believe is an error in a tutorial. I am doing this so that others who may be perplexed by why the code snippet is not working as expected have some additional information.

I have every expectation that once I find the Rev 2 schematic the fact that the pixels are ON when a logic LOW is written will make sense. That understanding does not address what looks to be an error in the tutorial.

1 Like
10

Ok, but the RGBLED are "onboard" to the Arduino Nano 33 BLE Sense 2.

11

Nano 33 BLE Sense Rev 2-schematics.pdf (1.4 MB)
Here is the BLE Sense Rev 2 schematic. Thank you for your patience.

1 Like
12

I see from the schematic that the common leg is +3V3 for DL3.
So that's the technical reason why a logic LOW turns on the pixels.

I apologize for not not clearly stating my intent in this posting which was to correct the tutorial which states that a logic HIGH turns on the pixels.
Now the reason for this situation is explained.
Thank you all for your help.

13

Oh... sorry. Now I understand.

14

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