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Added individual led brightness option to led strip #73

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Added individual led brightness option to led strip #73

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eb5a03d
Merge pull request #1 from androidthings/master
plattysoft Sep 18, 2017
9066f46
added invidual brightness setting per led
plattysoft Sep 18, 2017
903b118
added invidual brightness setting per led
plattysoft Sep 18, 2017
1b58fec
separating the individual and global brightness concepts
Sep 19, 2017
35b243c
updating method name in tests
Sep 19, 2017
0dc3695
fixed code style
Sep 19, 2017
96fc125
added check of array sizes
plattysoft Sep 19, 2017
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40 changes: 35 additions & 5 deletions apa102/src/main/java/com/google/android/things/contrib/driver/apa102/Apa102.java
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,16 @@ public enum Direction {
private Mode mLedMode;

// RGB LED strip settings that have sensible defaults.
private int mLedBrightness = MAX_BRIGHTNESS >> 1; // default to half
private int mLedBrightnessGlobal = MAX_BRIGHTNESS/2;
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@jdkoren jdkoren Sep 18, 2017 •
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nit: This was changed to division, while the ones below are still using shift. Perhaps revert this line?

private int mLedBrightness[] = new int[] {
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@jdkoren jdkoren Sep 18, 2017

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This array has 7 elements, is it because the RainbowHAT has 7 LEDs? I don't think it's good to assume that users of this driver are also using the RainbowHAT or that they have a certain number of LEDs connected.

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@Fleker Fleker Sep 18, 2017

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+1
For example, the ReSpeaker 2-Mic Hat has Apa102 LEDs but only three of them.

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@plattysoft plattysoft Sep 19, 2017

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Good point. I was thinking only of the one on the Rainbow HAT. I'll change it to behave in the same way as the values.

MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1,
MAX_BRIGHTNESS >> 1
}; // default to half

// Direction of the led strip;
private Direction mDirection;
Expand Down Expand Up @@ -162,14 +171,35 @@ public void setBrightness(int ledBrightness) {
throw new IllegalArgumentException("Brightness needs to be between 0 and "
+ MAX_BRIGHTNESS);
}
mLedBrightness = ledBrightness;
mLedBrightnessGlobal = ledBrightness;
for (int i=0; i<mLedBrightness.length; i++) {
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@jdkoren jdkoren Sep 18, 2017

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I would say use Arrays.fill here, but see the comment about keeping global brightness and individual brightness separate.

mLedBrightness[i] = mLedBrightnessGlobal;
}
}

/**
* Sets the brightness for all LEDs in the strip.
* @param ledBrightness The brightness of the LED strip, between 0 and {@link #MAX_BRIGHTNESS}.
*/
public void setBrightness(int[] ledBrightness) {
mLedBrightnessGlobal = 0;
for (int i=0; i<mLedBrightness.length; i++) {
if (ledBrightness[i] < 0 || ledBrightness[i] > MAX_BRIGHTNESS) {
throw new IllegalArgumentException("Brightness needs to be between 0 and "
+ MAX_BRIGHTNESS);
}
mLedBrightness[i] = ledBrightness[i];
if (mLedBrightnessGlobal < ledBrightness[i]) {
mLedBrightnessGlobal = ledBrightness[i];
}
}
}

/**
* Get the current brightness level
* Get the current brightness maximum level
*/
public int getBrightness() {
return mLedBrightness;
return mLedBrightnessGlobal;
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@jdkoren jdkoren Sep 18, 2017

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I don't like that we can only provide one value here. To me it makes better sense to add a int getBrightness(int index) (or a int[] getBrightnessArray()), which then makes me think we should not try to have global brightness and individual brightness be synchronized at all: either the user uses global brightness, or the user uses individual brightness. (Assuming that's the way forward, we could use the global brightness by default.)

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@plattysoft plattysoft Sep 19, 2017

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yes, we can return an array of int, then we can be consistent about returning the array of brightness as it is or null if only global brightness is set. I do think that keeping them in sync makes sense as long as the logic is clear. Also, I agree. I do not expect a developer to mix them on the same project.
Will do some changes later today.

}

/**
Expand Down Expand Up @@ -212,9 +242,9 @@ public void write(int[] colors) throws IOException {
pos += APA_START_FRAME_PACKET_LENGTH;

// Compute the packets to send.
byte brightness = (byte) (0xE0 | mLedBrightness); // Less brightness possible
final Direction currentDirection = mDirection; // Avoids reading changes of mDirection during loop
for (int i = 0; i < colors.length; i++) {
byte brightness = (byte) (0xE0 | mLedBrightness[i]); // Less brightness possible
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@jdkoren jdkoren Sep 18, 2017

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This line will throw index out of bounds exception if colors.length is larger than mBrightness.length. We would need to decide how to handle this (fallback to some value? throw an exception?).

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@plattysoft plattysoft Sep 19, 2017

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in this case I think an Index out of bounds exception is fine (after the changes). The developer is passing two arrays, one for brightness and one for colors, both should be of the same length.

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@jdkoren jdkoren Sep 19, 2017

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I'm not sure throwing an exception is the best option. This method previously could never throw that exception, so ideally we wouldn't change that behavior. (Even if we do decide to throw, we should be the ones throwing it so that we can provide an appropriate message.)

One alternative, for example, would be to repeat the final brightness value.

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@plattysoft plattysoft Sep 19, 2017

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I'm more in favor of returning an exception of the length of the arrays is different, so it does not behave unexpectedly, will implement that later.

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@plattysoft plattysoft Sep 20, 2017

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so, @jdkoren I think this is good now, right?

int di = currentDirection == Direction.NORMAL ? i : colors.length - i - 1;
copyApaColorData(brightness, colors[di], mLedMode, mLedData, pos);
pos += APA_COLOR_PACKET_LENGTH;
Expand Down
14 changes: 14 additions & 0 deletions apa102/src/test/java/com/google/android/things/contrib/driver/apa102/Apa102Test.java
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,20 @@ public void setBrightness_throwsIfTooLarge() throws IOException {
leds.setBrightness(Apa102.MAX_BRIGHTNESS + 1);
}

@Test
public void setBrightnessArray_throwsIfTooSmall() throws IOException {
Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);
mExpectedException.expect(IllegalArgumentException.class);
leds.setBrightness(new int[] {-1});
}

@Test
public void setBrightnessArray_throwsIfTooLarge() throws IOException {
Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);
mExpectedException.expect(IllegalArgumentException.class);
leds.setBrightness(new int[] {Apa102.MAX_BRIGHTNESS + 1});
}

@Test
public void setDirection() throws IOException {
Apa102 leds = new Apa102(mSpiDevice, Apa102.Mode.BGR, Apa102.Direction.NORMAL);
Expand Down