lesson 01 - working with the Pico W

Getting started with your Pico

Let's flash your Pico.

We'll be following this guide from learn.adafruit.com

Plug your Pico in via USB with the cable from your kit.
If the Pico does not appear in your file explorer, unplug the Pico, hold the reset button and then plug the Pico back in. After 2-3 seconds, release the reset button. You should hear a tone as the device registers with your laptop.
Return to file explorer. In the RPI-RP2 mount you will see 2 files, index.htm and info_uf2.txt.
- index.htm will redirect you to the Raspberry Pi official site
- info_uf2.txt will give you version information for the currently installed firmware on the board.
From within your CircuitPython-bins folder (in Downloads), drag the UF2 file onto the RPI-RP2 device. This will cause the device to load the updated bootloader and restart. The file may take 30-40 seconds to copy.
When the device has rebooted, you should now see a device named CIRCUITPY in your file explorer.
Congratulations, you have flashed your board and it now is running Cirucit Python.

If you explore the device from your file explorer, you'll see a new arrangement of files, as follows:

lib folder - contains library / module files from Adafruit and the Community bundles to make interacting with components easier
boot_out.txt - provides firmware, serial number and mac address information
code.py - this is the default filename the board will expect to see that will containe the code it will execute
settings.toml - an empty file for now

Let's get into Mu

Head over to your downloads folder, and double click on the MuEditor file with your Pico connected via USB. This will launch the coding environment we'll use for our work.

The first load will take a few minutes
When the editor is launching, you may be prompted for an environment to select, pick Circuit Python.

Example 01

Hello World with onboard LED

Reference Links

Code
About

# Import libraries necessary for functionality
import board
import digitalio
import time

# Define a LED object (onboard LED) and setup it's directionality
led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

# Create an infinite loop and manipulate the LED then sleep
while True:
  led.value = True
  time.sleep(0.75)
  led.value = False
  time.sleep(0.75)

Example 02

Hello World with external LED

Approach
- We'll use the 3V3 (3.3 volts DC) output on the Pico to supply power to the project
- We need to determine how much resistance is needed to not overwhelm the Red LED (note, different colored LEDs have different values)
  - Red LED Sample Spec Sheet
  - We need to know the forward current (I_F) and the forward voltage (V_F)
  - From the spec sheet, we find I_F to be 20 mA and V_F to be 1.8-2.2V
  - Given Ohms Law (the equation _V = I _ R), we can derive the necessary value for R
    - R = (V_Supply - V_F) / I
      - Note: V_Supply is the supply voltage from the Pico
    - R = (3.3V - 2V) / .02 = 130 Ohms
    - We don't have a 130 Ohm resistor in the kit, so we go to the next higher value available, 220 Ohm
    - Looking at the resister decoder, we see 220R is red-red-black
    - V = Volts | I = Current (Amps) | R = Resistance (Ohms)
    - Using an oversized resistor with LEDs is fine, the LED will appear dimmer than it's maximum value
Wiring
- Do not connect the Pico to USB at this point, it should be disconnected from any power source
- Insert the pico into the Freenove Breakout Board for the Pico
- Loosen the terminals near the top right for GND, 3V3 and GP20
  - Reference: Raspberry Pi Pico W Pinouts
- Connect a black hookup wire to GND to the negative (-) rail of the breadboard
- Connect a red hookup wire to 3V3 to the positive (+) rail of the breadboard
- Connect a blue hookup wire to GP20 to row 13f of a the breadboard
- Connect the Anode (long leg, +) of the LED to an open position on row 13
- Connect the Cathode (short leg, -) of the LED to an open position on row 16
- Connect one leg of a 220R to row 16
- Connect the other leg of a 220R to the negative (-) rail of the breadboard
Code
- In Mu, enter the following code and save the file as code.py to the Pico

# Import libraries necessary for functionality
import board
import digitalio
import time

# Define a LED object (on pin GP20) and setup it's directionality
led = digitalio.DigitalInOut(board.GP20)
led.direction = digitalio.Direction.OUTPUT

# Create an infinite loop and manipulate the LED then sleep
while True:
  led.value = True
  time.sleep(0.75)
  led.value = False
  time.sleep(0.75)

The above code block can be found here.

Last step - Connect the USB port on the Pico to the USB port on your laptop. This will supply the Pico with 5VDC of supply voltage - Note that as the Red LED illuminates on the breadboard, the yellow LED on the breakout board illuminates to let you know current is flowing through the GP20 GPIO pin

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