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Programming

Programming#

Start by opening EVN’s ButtonLED example sketch in Arduino (File > Examples > EVN > 01.Basics > buttonLED).

Board Selection#

To upload to EVN Alpha, select EVN Alpha as your board (Tools > Board > Raspberry Pi RP2040 Boards > EVNAlpha). Setting the right board ensures that the USB Serial connection and upload process are stable.

USB Drive (BOOTSEL) Mode#

Next, we will set the board to appear as a USB Mass Storage Drive to the computer, ready for upload. RP2040 and other Pico-related docs call this BOOTSEL mode, but we prefer to call it USB Drive mode.

In this mode, any previously uploaded programs are also stopped from running.

There are 2 ways to set the board into USB Drive mode:

  1. Reset and BOOTSEL (Faster)

    • Press and Hold the Reset Button

    • Press and Hold the BOOTSEL Button

    • Release the Reset Button

    • Release the BOOTSEL Button

  2. Power and BOOTSEL (Easier)

    • Set the board to Off mode using On/Off Button

    • Press and Hold the BOOTSEL Button

    • Set the board to On mode using On/Off Button

    • Release the BOOTSEL Button

Now, the board should appear as a USB Drive when connected to your computer, and it will appear as a UF2 Board option in Tools > Port. Select it, and upload your code.

After your new code has been uploaded, look through the available ports in Tools > Port again. If the code runs properly, a COM Port with a label (e.g. COM7 (Raspberry Pi Pico W)) should be available for you to upload with and access on Serial Monitor.

Uploading#

After selecting the correct board, press the Upload button (right arrow) in the top left corner. For fresh installs of the Arduino-Pico core and EVN library, the first compile may take a while, but subsequent uploads should take less time.

When you press the User Button (leftmost one), the blue User LED should toggle on and off!

COM Port Selection#

Once the code has been uploaded, the board will cease to appear as a USB Drive. Instead, under Tools > Port, you should be able to see a COM Port available with a label (e.g. COM3 (Raspberry Pi Pico W)). Select it, and you will be able to communicate with the program using the Serial Monitor.

Note

If a COM Port is not available, it may be due to incorrect Board Selection settings, or a crashed program. Set the board to USB Drive mode again, and try to upload a different program.

Writing Your First Sketch#

To start, include the EVN library using #include <EVN.h> in your program.

All EVN sketches will use the board class EVNAlpha for built-in functions. Aside from this class, there are classes for each of our Standard Peirpherals.

This is what an example sketch with 2 motors and 2 colour sensors would look like:

#include <EVN.h>

EVNAlpha board;
EVNMotor motor_left(3, EV3_LARGE),
         motor_right(2, EV3_LARGE);

EVNColourSensor cs1(1), cs2(2);

void setup()
{
    //board.begin() is always at the start of void setup()
    board.begin();

    cs1.begin();
    cs2.begin();
}

void setup1()
{
    //motor begin can be called on 1st core, but calling on 2nd core improves performance
    motor_left.begin();
    motor_right.begin();
}

void loop()
{
    int cs1_reading = cs1.readClear();
    int cs2_reading = cs2.readClear();

    //do something with colour sensor readings here

    motor_left.runSpeed(600);
    motor_right.runSpeed(600);
}

More examples can be found in the EVN library examples (File > Examples > EVN…).

Uploading Shortcuts#

The basic process of uploading is listed as above:

  1. Set board settings (if not already set)

  2. Set board to USB Drive mode

  3. Select UF2 Board in Tools > Port

  4. Upload Code

  5. Select COM Port to use Serial Monitor

The Arduino-Pico core does introduce some ways to make this process faster:

  • After the upload button is pressed, the IDE should automatically detect any board in USB Drive mode and upload to it, making step 3 unnecessary

  • If the board is not in USB Drive mode, but its program has not crashed and the board is connected with its COM Port correctly set before the upload button is pressed,

    the IDE should automatically detect the board and upload to it, making steps 2 and 3 unnecessary

  • If you add rp2040.enableDoubleResetBootloader() inside void setup()/ void setup1() or void loop()/ void loop1(), pressing the Reset button twice will set the board to USB Drive mode, making step 2 much easier.

    Getting the correct timing for this may take a few tries; it will not enter USB Drive mode if double-tapped too quickly or too slowly.

Since these “shortcuts” can fail for a variety of reasons (crashed code, USB inconsistencies from computer to computer or different operating systems), we cannot endorse them as foolproof upload methods that work 100% of the time. So if they do fail, follow the basic uploading process and everything should work.

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