Week 4, Embedded Programming¶

Assignment¶

Group assignment¶

Demonstrate and compare the toolchains and development workflows for available embedded architectures
Document your work to the group work page and reflect on your individual page what you learned

Individual assignment¶

Browse through the datasheet for your microcontroller
Write a program for a microcontroller, and simulate its operation, to interact (with local input &/or output devices) and communicate (with remote wired or wireless connection)

Checklist¶

from Nueval

Linked to the group assignment page
Browsed and documented some information from utilized microcontroller data sheet
Programmed your simulated board to interact and communicate
Described the programming process(se) used
Included source code
Included hero shot(s)

Group work¶

For our work at Fab Lab Reykjavik (FLR), we split tasks for the overall group. My work was to explain how to program an RP-2040 microprocessor with micropython in VSCode.

See my contribution in the “Micropython, VSCode and RP2040 programming” on our Fab Lab Reykjavik group page.

Individual work¶

Processor¶

Based on suggestion from my instructor, I am first working with an RP-2040. This is a small, yet powerful microcontroller designed by Raspberry Pi. The naming derives from the following:

RP2040 name explanation. Source

This processor supports micropython, which is another reason for my choosing this. I have experience with Python, and the learning curve should hopefully be easier.

More specifically, I will be working with an RP-2040 from Seeed Studio. Their documentation page noted the following specifications.

Item	Value
CPU	Dual-core ARM Cortex M0+ processor up to 133MHz
Flash Memory	2MB
SRAM	264KB
Digital I/O Pins	11
Analog I/O Pins	4
PWM Pins	11
I2C interface	1
SPI interface	1
UART interface	1
Power supply and downloading interface	Type-C
Power	3.3V/5V DC
Dimensions	21×17.8×3.5mm

Seeed Studio XIAO RP2040 Specs

There is a USB-C connection which can power the board, and also be used for data transfer.

Image of Seeed Studio XIAO RP2040. Source

The design is open, yet the detailed specifications can be noted from the Raspberry Pi foundation. The RP2040 has a deep power and flexibility in its design. Details can be seen from the Raspberry PI RP2040 specification page and the datasheet.

The microprocessor has two cores, which allow for parallel processing. For coding, both coding with MicroPython and C/C++ are supported. The MCU supports both internal pull-up and pull-down resistors, lessen needs for resistors in the circuit design. The pins support 5V input. Four pins supporting analog and digital conversion. There are onboard LEDs, including a multicolor one. Together, this makes for a very flexible and powerful microprocessor for development.

Simulators and development¶

Looking forward to my final project, my instructor suggested I work with an RP-2040. To emmulate code, I am using VSCode. To accomplish that, the Wokwi extension for VSCode needs to be installed. Search for that and install.

To get the extension working, one needs a wokwi.toml file in the directory, which contains:

[wokwi]
version = 1
gdbServerPort = 3333
firmware = "firmware/RPI_PICO-20241129-v1.24.1.uf2"
elf = "firmware/RPI_PICO-20240602-v1.23.0.uf2"

The firmware is the same one noted in the group page. The path to the firmware needs to be relative to the wokwi.toml file.

After saving this file, there is a button to get a Wokwi license.

The click takes you to the Wokwi website, and there is a notice that the license is free for open source project. On that page, click the ‘generate license’ button. Then one can push a subsequent button to install into VSCode. I pushed that, and the license installed.

This seems to be a dead end. Whenever I try to edit, I am told that I need to upgrade to a paid license to edit in VSCode.

Online we go.

Simulating motor¶

Having moved online, work was done at wokwi.com. My working project can be seen at in this project.

I wanted to work towards functions I would need for my final project. To deal cards, I need motors to rotate and deal the cards, and I want to track the number of cards. The dealer will be activated by pushing buttons.

First I made a Wokwi simulator that responded to a button push. It runs continuously, and the state changes when the button is pushed.

Then, I figured out how to attach a motor. This is based on an A4988 class found on Wokwi. The options for motors and control were limited in the simulator. With a button push, the motor is moved one half rotation. A counter was added for number of pushes, which also included a 2nd button. For the 2nd button, the motor rotates in the reverse direction.

Then a 2nd motor was added, making the 2nd player work go to a separate motor. I also added an LCD display to show the current state. The LCD work was based on an LCD class found on Wokwi. The example did not work, but gave enough hints to make a working version.

Here is a video of my simulator setup. It contains two buttons, one for each of two players. When each button is pushed, the respective counter is incremented, and the right motor moves a half turn.

Card dealing simulator in action

The following code runs the simulator. This code relies upon external classes, which I utilized from other wokwi projects.

To control the motor, I utilized an A4988 class from project to rotate a stepper motor. This example rotates a motor back and forth continuously. With the use of buttons, I made controlled half-rotations.
For a display, I utilized an LCD class from a project to use an LCD display. This project did not work, but gave enough guidance to make a working display.

from machine import Pin, SoftI2C

# A4988 work based on https://wokwi.com/projects/397750005824230401
from a4988 import A4988  # Importing the A4988 class from a4988.py

# LCD work based on https://wokwi.com/projects/390084353519159297
from i2c_lcd import I2cLcd

# Create motors from A4988 class
stepper0 = A4988(0,1)
stepper1 = A4988(20,21)
print("Starting stepper motor test.")
speed = 200

# Set up buttons
button0 = Pin(2, Pin.IN, Pin.PULL_UP)
button1 = Pin(12, Pin.IN, Pin.PULL_UP)

# Starting buttons state
# Buttons go to 0 when pushed
lastState0 = 1
lastState1 = 1

# Starting counts
count0 = 0
count1 = 0

# Pins for LCD display
sdaPIN = 18
sclPIN = 19

# Set up i2c LCD
i2c = SoftI2C(sda=sdaPIN, scl=sclPIN, freq=10000)

# Scan for display devices
devices = i2c.scan()

# Only one display, set up 2x16 display
lcd = I2cLcd(i2c, devices[0], 2, 16)
lcd.putstr("Start dealing!")



while True:

    # Read buttons
    # Pushing button makes value 0
    state0 = button0.value()
    state1 = button1.value()

    # Test for changed state button 1
    if(state0 != lastState0):
      # Test if button pushed
      if state0 == 0:
        # Increment count for player 1 cards
        count0 += 1
        # Print state to terminal
        print(f"Player 1: {count0}\nPlayer 2: {count1}\n")
        # Print motor to deal card
        stepper0.move_sync(100, speed)
        # Clear LCD
        lcd.clear()
        # Put count on LCD
        lcd.putstr(f"Player 1: {count0}\nPlayer 2: {count1}")
      # Set tracked state to current state
      lastState0 = state0

    # Test for changed state button 2
    if(state1 != lastState1):
      # Test if button pushed
      if state1 == 0:
        # Increment count for player 2 cards
        count1 += 1
        # Print state to terminal
        print(f"Player 1: {count0}\nPlayer 2: {count1}\n")
        # Print motor to deal card
        # Player 2 motor moves opposite direction to P1
        stepper1.move_sync(-100, speed)
        # Clear LCD
        lcd.clear()
        # Put count on LCD
        lcd.putstr(f"Player 1: {count0}\nPlayer 2: {count1}")
      lastState1 = state1

The full set of files needed for the simulator;

Main code: main.py
Wokwi layout: diagram.json
LCD display: i2c_lcd.py and lcd_api.py
Motor control class: a4988.py

Possible improvements

Both the buttons and motors could be classes, as I am currently duplicating code.
In my final project, I am anticipating rotating the dealer to player positions, and dealing in that manner. Then, one motor to rotate, and one to deal.