design products & applications – August 2019

C was intentionally designed to be
mapped easily into machine instructions
for a target processor. This bias towards
the needs of the machine over those
of the programmer is apparent in the
language’s syntax.

Python is also an object-oriented lan-
guage. Python’s syntactical design em-
phasises code readability – for humans

• which is one key difference between
  Python and C++. Writability, closely as-
  sociated with readability, is another trait
  in Python’s favour. Writability means that
  Python is generally credited with allow-
  ing programmers to write applications
  more quickly.

A second major difference is that Py-
thon is an interpreted language. Like
Basic, the interpretive nature of Python
encourages experimentation, and there-
fore learning by dispensing with the edit/
compile/download/run development cy-
cle used for compiled programming lan-
guages. However, unlike Basic, Python
is a modern, higher level, object-ori-
ented language that incorporates half
a century’s worth of advances in com-
puter science that have appeared since
Basic was first developed.

For example, Python’s variables need
not be declared or typed before use.
Programmers need not worry whether a
variable should be an integer or a float-
ing-point number. The Python interpret-
er figures it all out and makes the appro-
priate choices at run time.

Two more differences between C++
and Python are string handling and
punctuation. Many programmers find
string handling in C++ to be obtuse
and confusing. Python’s string handling
is much simpler and very reminiscent
of Basic’s simple and well-liked string
handling capabilities.

Similarly, C and C++ punctuation – es-
pecially curly braces ({}) – are another
frequent stumbling block for new and
even experienced programmers. It feels
like there are always an odd number of
curly braces in a program, which means
the programmer must dig into the code
to find where the missing curly brace
should go. Python has no such finicky

punctuation, but it does use indentation,

which gives Python code its readability.

The origins of MicroPython

Like C and C++, Python was originally

designed to run on larger computers.

Consequently, the language required

too many resources to be used for

programming microcontrollers. Australian

programmer and physicist Damien George

therefore developed a version of Python

called MicroPython that could run on a

microcontroller’s more limited resources.

MicroPython’s interactive nature centres

on its command interface, formally called

the REPL (read-eval-print-loop) window,

which usually operates over a serial

connection that connects a host PC to

a microcontroller dev board. The REPL

interface accepts user inputs, evaluates

them, and then either returns results to the

user through the REPL window or performs

the command embedded in the statement.

Using the REPL interface, it’s possible

to query a variable, toggle an I/O line, or

send a string of characters to an attached

peripheral. The line is interpreted and

immediately executed as soon as the

enter key is pressed.

CircuitPython support for

dev boards

Each microcontroller has a unique set of

peripherals, and each dev board adds to

that list. These peripherals require support

libraries. This is true for both the Arduino

IDE and for MicroPython. In addition, there

are many add-on peripheral devices, like

Adafruit’s 1655 NeoPixel addressable

RGB LED, that also require library support.

To provide a higher degree of support,

Adafruit has developed its own version

of MicroPython, called CircuitPython.

The company has also converted many

peripheral libraries from its immense

Arduino collection to CircuitPython libraries.

Adafruit designed a line of microcontroller

dev boards explicitly to support CircuitPy-

thon.

These include:

• 3333 Circuit Playground Express with
  ten addressable, controllable RGB
  LEDs (Figure 1)
  
  
  • 3500 Trinket M0 dev board that
    measures only 27mm x 15.3mm x
    2.75mm (Figure 2)
  
  
  • 3501 Gemma M0 is about the size
    of a US 25 cent piece (a quarter) and
    can be powered from its USB port or a
    separate battery port (Figure 3)
  
  
  • 3403 Feather M0 Express is a dev
    board that features a small breadboard
    area for custom circuitry (Figure 4)
  
  
  
  

These four Adafruit microcontroller dev

boards are all based on Microchip Tech-

nology‘s SAMD21 microcontrollers with

native USB support. Furthermore, versions

of CircuitPython for other dev boards with

other microcontrollers are also starting to

appear, including Adafruit’s 3406 Feath-

er NRF52 and Nordic Semiconductor’s

nRF52-DK dev boards, both based on

Nordic Semiconductor’s nRF52832 micro-

controller. Additionally, Nordic Semicon-

ductor’s nRF52840-DK dev board, based

on the company’s nRF52840 microcon-

troller, is also supported by CircuitPython.

Both microcontrollers upon which these

three boards are based have Bluetooth

Feature: Rapid microcontroller-based prototyping

dpaonthenet.net 27

Figure 3: Adafruit’s 3501 Gemma M0 is small and can be powered

from its USB port or a separate battery port. (Image source: Adafruit)

Figure 2: Adafruit’s 3500 Trinket M0 dev board measures only 27mm

x 15.3mm x 2mm. (Image source: Adafruit)