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more work on LED screen doc

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Tom Ball 2016-06-13 21:58:08 -04:00
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docs/device/screen.md
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@ -13,10 +13,15 @@ The micro:bit LED screen
``` ```
The micro:bit LED screen consists of 25 red LED lights arranged in a 5X5 grid (5 LEDs across by 5 LEDs down). The micro:bit LED screen consists of 25 red LED lights arranged in a 5X5 grid (5 LEDs across by 5 LEDs down).
In the screen above, we created a checkerboard pattern using the LEDs.
### Which LED? ### Which LED?
You use ``x , y`` coordinates to specify a particular LED in the grid; where ``x`` is the horizontal position and ``y`` is the vertical position (0, 1, 2, 3, 4). To figure out the ``x``, ``y`` coordinates, position your micro:bit horizontally, like a credit card (see picture above). You use `(x ,y)` coordinates to specify a particular LED in the grid;
where `x` is the horizontal position (0,1,2,3,4) and `y` is the vertical position
(0, 1, 2, 3, 4).
To figure out the ``x``, ``y`` coordinates, position your micro:bit horizontally, like a credit card (see picture above).
Here are the x, y coordinates for the LEDs in the 5X5 grid: Here are the x, y coordinates for the LEDs in the 5X5 grid:
@ -30,11 +35,17 @@ Here are the x, y coordinates for the LEDs in the 5X5 grid:
`(0,4)` `(1,4)` `(2,4)` `(3,4)` `(4,4)` `(0,4)` `(1,4)` `(2,4)` `(3,4)` `(4,4)`
The x, y coordinates for the LED in the centre of the grid are `2, 2`. Starting from `0, 0` count over 2 columns and then down 2 rows. The x, y coordinates for the LED in the centre of the grid are `(2,2)`. Starting from `(0,0)` count over 2 columns and then down 2 rows.
### Check your understanding
Which LEDs are turned on in the checkboard pattern above?
### Row, column - 1 ### Row, column - 1
Since the row and column numbers start at 0, an easy way to figure out the x, y coordinates is to subtract 1 from the row and column number (when counting from 1). In other words, to specify the LED in the 4th column 5th row, subtract 1 from each number to get coordinates `3, 4`. Since the row and column numbers start at 0, an easy way to figure out the (x,y) coordinates
is to subtract 1 from the row and column number (when counting from 1).
In other words, to specify the LED in the 4th column 5th row, subtract 1 from each number to get coordinates `(3,4)`.
### Turn a LED on/off ### Turn a LED on/off
@ -42,8 +53,11 @@ Use [plot](/reference/led/plot) and [unplot](/reference/led/unplot) to turn a LE
```blocks ```blocks
led.plot(0,0); led.plot(0,0);
led.plot(1,1);
basic.pause(1000); basic.pause(1000);
led.unplot(0,0) led.unplot(0,0);
basic.pause(1000);
led.unplot(1,1);
``` ```
### Is a LED on/off? ### Is a LED on/off?