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Case 05：Flashlight

Our Goal

  • Use watch kit to create a wearable flashlight.

Material

Hardware Connection

Plug the LED ring into power:bit just like the picture below.

Software

Microsoft Makecode

Programming

Step 1

  • Click Advanced in the code drawer of MakeCode to see more options.

  • To program for the LED ring, we have to add a package. Find Add Package in the bottom of code drawer and click it. This will pop up a dialogue box. Search for "neopixel" and click to download this package.

Note: If you get a hint that some packages will be deleted due to the problem of incompatibility, you can either follow the prompts, or create a new project in the project menu.

Step 2

  • When start our program, create a variable flag and set its value to 0.
  • When button A is pressed, set the value of the variable flag to 1.
  • When button B is pressed, set the value of the variable flag to 2.
  • When button "A+B" is pressed, set the value of the variable flag to 0.

Step 3

  • Create a forever loop to continuously judge if statements.
  • When flag equals to 1，call function light(turn on 3 LEDs); when flag equals to 1 and button A is pressed, call function light_02(All LEDs turned on).
  • When flag equals to 2，call function police(simulate alarm light).
  • When flag equals to 0，call function true off to turn off all LEDs.

Step 4

  • Function light allows 8 LEDs connected to P2 port and turns on the LED number 4~6 with white light.

  • Function light_02 will turn on all LEDs.

  • Function police allows number 0~4 LEDs become blue and number 4~8 LEDs become red. Each section delays for 0.1 second.

  • Function true off will turn off all LEDs.

Program

Result

Press button A, all LEDs on LED ring are turned on.
Press button B, LEDs are flashing.
Press button A+B, all LEDs are turned off.

Think

Q: Why the LED light looks yellow while in the code it is white?
A: Due to the insufficient battery power, the current can't support to drive the LED ring.

Relative Readings