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Pin names were out of sync with the pictures in the Make section... (#390)

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Ended up editing the rest of the text for clarity.  Please let a native English speaker check the language.
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Leo Gordon 2017-04-25 01:45:28 +01:00 committed by Peli de Halleux
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docs/projects/telegraph/code.md
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@ -1,33 +1,34 @@
# Code
Let's build the code that will send a impulse while the user presses ``A``.
Let's build the code that, when the user presses the button ``A`` on a @boardname@, will send an impulse over a wire to the receiving @boardname@ and turn an LED on there.
Make sure that the sending and receiving wires run symmetrically across: pin ``P1`` on one @boardname@ is connected to pin ``P2`` on the other, and vice versa, as shown on the pictures in the "Make" section. This way we can use the same code on both @boardname@s .
### Step 1
We now need to digitally write to pin ``P0`` as **high** (1).
We start with a block that digitally writes **high** (value ``1``) to the sending @boardname@'s pin ``P1``. This block can be found in _Pins_ drawer of the Advanced section.
```blocks
pins.digitalWritePin(DigitalPin.P0, 1)
pins.digitalWritePin(DigitalPin.P1, 1)
```
### Step 2
We want to add a block to turn on an LED in the middle area of the LED display using plot x, y.
So insert the appropriate LED plot x, y.
To show what we are sending, we add a block to turn on an LED in the centre of the LED display (2,2) using _plot x, y_ :
```blocks
pins.digitalWritePin(DigitalPin.P0, 1)
pins.digitalWritePin(DigitalPin.P1, 1)
led.plot(2, 2)
```
### Step 3
We want to insert a condition that tells us when to turn on the LED. So insert the if block under logic drawer.
Then add a condition that occurs if we do not turn on a LED with plot x, y. We also should plot an LED on the display if button A is pressed. Your code should appear as follows:
Now that we know how to send the signal, we only want to be doing it while the button ``A`` is pressed.
Pick an _if_ block from the _Logic_ drawer (you'll need the version with _else_ part that will remain empty for now). Add a check whether the button ``A`` is pressed from the _Input_ drawer and move the blocks from the previous step into _then_ part :
```blocks
if (input.buttonIsPressed(Button.A)) {
pins.digitalWritePin(DigitalPin.P0, 1)
pins.digitalWritePin(DigitalPin.P1, 1)
led.plot(2, 2)
} else { }
```
@ -35,54 +36,58 @@ if (input.buttonIsPressed(Button.A)) {
### Step 4
We want to write code if button A is NOT pressed. It is important to say that digital write is not on. We also want to turn off all the LED light.
For the _else_ branch (while the button A is not pressed) we want to do the opposite of what we did in the _then_ branch: take the value of pin ``P1`` to **low** (0) and unplot the corresponding LED on the sending @boardname@ :
```blocks
if (input.buttonIsPressed(Button.A)) {
pins.digitalWritePin(DigitalPin.P0, 1)
pins.digitalWritePin(DigitalPin.P1, 1)
led.plot(2, 2)
} else {
pins.digitalWritePin(DigitalPin.P0, 0)
pins.digitalWritePin(DigitalPin.P1, 0)
led.unplot(2, 2)
}
```
### Step 5
Let's add a forever loop so this code runs in the background forever. Modify your code so that your code looks like this. Run the code and press Button A.
Let's wrap it all in a forever loop so this code runs in the background, forever checking the button ``A`` and sending the appropriate signal to the receiver.
Modify your code so that your code looks like this. Download the code into one of the @boardname@s, press and release button ``A`` a few times.
```blocks
basic.forever(() => {
if (input.buttonIsPressed(Button.A)) {
pins.digitalWritePin(DigitalPin.P0, 1)
pins.digitalWritePin(DigitalPin.P1, 1)
led.plot(2, 2)
} else {
pins.digitalWritePin(DigitalPin.P0, 0)
pins.digitalWritePin(DigitalPin.P1, 0)
led.unplot(2, 2)
}
})
```
The sending part is done, so we are going to add the receiving part.
### Step 6
We now need to digitally read to the specified pin (P1) as digital. Let's start by going to the pin drawer and adding digital read pin (0,1) and changing the pin to P1. Now we need to create a condition for digital read pin (0,1). So we go to the logic drawer and select the comparison operator. Then we want to set the comparison operator to 1 to turn on digital read on pin 1. We want to insert a condition that tells us if button A is pressed and we should turn on digital read on pin 1. So insert the if block under logic drawer. Then add a condition that occurs if digital read on P1 is on. Then we want to plot x, y at the x, y coordinates of 2,2. we also want to say that if digital read pin P1 is not on, we want to turn off all LED lights on the screen. Your code should appear as follows:
The receiver needs to digitally read from the pin to which the sending @boardname@ will be writing (``P2``) over the wire. Let's start by going to the _Pin_ drawer, adding digital read pin ``P0`` and changing the pin value to ``P2``.
Now we want to examine the value read from ``P2`` and check whether it is **high** (value ``1``) or not. Go to the _Logic_ drawer, first pick an _if_ block, then come back for a comparison operator (=). Plug in our digital read block as one operand and the value ``1`` as the other.
We shall turn the LED in the bottom right corner (4,4) on to indicate that we received **high** and turn it off otherwise.
Your code should look as follows:
```blocks
if (pins.digitalReadPin(DigitalPin.P1) == 1) {
led.plot(4, 4);
}
else {
led.unplot(4, 4);
}
basic.forever(() => {
if (input.buttonIsPressed(Button.A)) {
pins.digitalWritePin(DigitalPin.P0, 1);
pins.digitalWritePin(DigitalPin.P1, 1);
led.plot(2, 2);
}
else {
pins.digitalWritePin(DigitalPin.P0, 0);
} else {
pins.digitalWritePin(DigitalPin.P1, 0);
basic.clearScreen();
}
if (pins.digitalReadPin(DigitalPin.P2) == 1) {
led.plot(4, 4);
} else {
led.unplot(4, 4);
}
});
```
@ -90,6 +95,6 @@ Your telegraph is ready!
### Step 7
* Connect the first @boardname@ to your computer using your USB cable and put the telegraph script on it.
* Connect the second @boardname@ to your computer using your USB cable and run the telegraph script on it.
* The first person and second person take turns pressing button A to play the telegraph game!
* Connect the first @boardname@ to your computer using your USB cable and download the telegraph script to it.
* Connect the second @boardname@ to your computer using your USB cable and download the telegraph script to it.
* The first person and second person can take turns pressing button A on their @boardname@s to play the telegraph game!