75 lines
2.4 KiB
Markdown
75 lines
2.4 KiB
Markdown
# On Data Packet Received
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Run part of a program when the @boardname@ receives a
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[number](/types/number) or [string](/types/string) over ``radio``.
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```sig
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radio.onDataPacketReceived(({receivedNumber, receivedString, time, serial, signal}) => { });
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```
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## ~hint
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To add or remove the parts of the packet from the block, try clicking the blue gear in the corner!
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## ~
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## Callback Parameters
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* ``packet`` - the [packet](/reference/radio/packet) that was received by the radio. The packet has the following properties:
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* `receivedNumber` - The [number](/types/number) that was sent in this packet or `0` if this packet did not contain a number. See [send number](/reference/radio/send-number) and [send value](/reference/radio/send-value)
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* `receivedString` - The [string](/types/string) that was sent in this packet or the empty string if this packet did not contain a string. See [send string](/reference/radio/send-string) and [send value](/reference/radio/send-value)
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* `time` - The system time of the @boardname@ that sent this packet at the time the packet was sent.
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* `serial` - The serial number of the @boardname@ that sent this packet or `0` if the @boardname@ did not include its serial number.
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* `signal` - How strong the radio signal is from `-128` (weak) to `-42` (strong).
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## Example
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This program keeps sending numbers that says how fast the @boardname@ is
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slowing down or speeding up. It also receives numbers for the same
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thing from nearby @boardname@s. It shows these numbers as a
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[bar graph](/reference/led/plot-bar-graph).
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```blocks
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basic.forever(() => {
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radio.sendNumber(input.acceleration(Dimension.X));
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})
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radio.onDataPacketReceived(({ receivedNumber }) => {
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led.plotBarGraph(receivedNumber, 1023);
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})
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```
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## Example
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This program uses the signal strength from received packets to graph the
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approximate distance between two @boardname@s.
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```blocks
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basic.forever(() => {
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radio.sendNumber(0)
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})
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radio.onDataPacketReceived(({ signal, receivedNumber }) => {
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led.plotBarGraph(
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Math.abs(signal + 42),
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128 - 42
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)
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})
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```
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## Troubleshooting
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The on radio data event can only be created once, due to the hardware restrictions.
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The radio set group might need to be set, synchronized , before the radio events will function.
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## See also
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[send number](/reference/radio/send-number),
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[send string](/reference/radio/send-string),
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[send value](/reference/radio/send-value),
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[set group](/reference/radio/set-group)
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```package
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radio
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```
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