lamp wrongly dark under very specific conditions, Uno 8 lamps krida

[distrakt]

Describe the bug

The sketch shows a bug I have seen in dimmable_lights.h

What I see is this:

If half the lamps are set to value X, and half are set to X+1,
and digitalRead() is in the sketch (even uncalled!)
then the ones set to X are displayed dark.

In this sketch I set them alternating ABABABAB, but I've
seen same behavior for AAAABBBB; likely any order.
If they're not half-and-half, the one with fewer
works ok. (or maybe one with greater, my observations
got confused)

Conditions:

Using 8 lamps on a Krida controller, on Arduino Uno
and ONLY if a digitalRead() function call is present,
even if the digitalRead() hasn't been called.

(Perhaps digitalRead() has some setup code or interrupt contention... ?)

Hardware and software used

• Library version: 1.6.1
• Arduino core: 1.8.6
• Enviroment/IDE: Arduino IDE 2.2.1
• Dimmer board: Krida 8
• Board: Arduino UNO, the classic

Using board 'uno' from platform in folder: /Users/poly/Library/Arduino15/packages/arduino/hardware/avr/1.8.6
Using core 'arduino' from platform in folder: /Users/poly/Library/Arduino15/packages/arduino/hardware/avr/1.8.6

---

I'm pasting the sketch in here, apologies if that isn't the convention, this is my first github bug report! :)

/**
david.van.brink@gmail.com 2024-02-23

This sketch shows a bug I have seen in dimmable_lights.h

What I see is this:

If half the lamps are set to value X, and half are set to X+1,
then the ones set to X are displayed dark.

In this sketch I set them alternating ABABABAB, but I've
seen same behavior for AAAABBBB; likely any order.
If they're not half-and-half, the one with fewer
works ok. (or maybe one with greater, my observations
got confused)

Conditions:

Using 8 lamps on a Krida controller, on Arduino Uno
and ONLY if a digitalRead() function call is present,
even if the digitalRead() hasn't been called.

*/

#include <dimmable_light.h> // library "Dimmable Light" 1.6

#define ALL_EIGHT_LAMPS 1 // bug happens if using 8 lamps. fewer works ok.
#define READPIN 12
#define INCLUDE_A_DIGITAL_READ 1

// the 8 pins used by the Krida 8-channel dimmer
DimmableLight dl1(11);
DimmableLight dl2(10);
DimmableLight dl3(9);
DimmableLight dl4(8);
#if ALL_EIGHT_LAMPS
DimmableLight dl5(7);
DimmableLight dl6(6);
DimmableLight dl7(5);
DimmableLight dl8(4);
#endif

void setup() {
DimmableLight::setSyncPin(3);
DimmableLight::begin();
pinMode(READPIN, INPUT_PULLUP);

Serial.begin(115200);
delay(200);
Serial.print("\n\n");
Serial.print("Dimmable Light bug with Krida 8 channel controller\n\n");
#if INCLUDE_A_DIGITAL_READ
Serial.println("digitalRead() is linked in, we see bug of half lamps off in some cases");
#else
Serial.println("no digitalRead(), all lamps appear on as desired & expected");
#endif
}

/// set lamps alternating brightnesses a and b
void setEm(uint8_t a, uint8_t b, uint16_t wait) {
Serial.print("lamps ");
Serial.print(a, HEX);
Serial.print(", ");
Serial.print(b, HEX);
Serial.println("");

dl1.setBrightness(a);
dl2.setBrightness(b);
dl3.setBrightness(a);
dl4.setBrightness(b);
#if ALL_EIGHT_LAMPS
dl5.setBrightness(a);
dl6.setBrightness(b);
dl7.setBrightness(a);
dl8.setBrightness(b);
#endif

delay(wait);
}

static int loops = 0;
void loop() {
loops++;

#if INCLUDE_A_DIGITAL_READ
// this wont actually do a read for a long, long time
// but just linking in the function seems
// to cause the four-lights-dark bug.
if(loops == 6000)
{
Serial.println("------> digital read happening! <------");
digitalRead(READPIN);
}
#endif

setEm(0x81, 0x80, 2000); // different by 1 step -- one lamp off
setEm(0x80, 0x81, 2000);
setEm(0x82, 0x80, 2000); // different by 2 steps, works ok

Serial.print(loops);
Serial.println(" completed. let's go again.");
}

[distrakt]

Completely acceptable workaround is to use FastGPIO library instead of the default arduino gpio functions.

But even still, I found some instability (slight occasional flicker) when lamps were near brightness to each other, especially trying to sweep them all together to a new brightness. A further workaround that helped is setBrightness(br & 0xfe), so lamps are not as close to each other in the interrupt timing.

This is on UNO; maybe not issue on faster cpu.