Make it with Micromite
Phil Boyce – hands on with the mighty PIC-powered, BASIC microcontroller
Part 37: Installing MMBASIC on a Raspberry Pi Pico
T
he MMBASIC programming
language has been extremely popular
over the last few years, appearing at
the heart of many PE projects (in the form
of a Micromite). This month, however, we
are going to show you how to install the
latest version of the MMBASIC firmware
into the low-cost (and readily available)
Raspberry Pi Pico. The result is a module
that we refer to as the ‘PicoMite,’ and we
really do believe it will become a regular
building-block in many future electronic
projects. Note that the PicoMite is not a
replacement for the Micromite; instead,
it is an alternative that is very quick to get
up and running.
So why are we so confident the PicoMite
will be useful? To begin with, the PicoMite
benefits from all the powerful features of
MMBASIC for the Micromite, especially
since it’s based on the Plus version of
MMBASIC which has more capability
than the Standard version. Also, compared
to a Micromite, the Pico module comes
preassembled, so the PicoMite is a true
‘plug-n-play’ module. (Remember, a
Micromite is essentially a Microchip PIC32
chip installed with MMBASIC but requiring
the assembly of a handful of additional
components to provide the relevant supply
voltages, pull-ups, and connectors.)
If you are familiar with using a Micromite,
then you’ll find using a PicoMite a breeze,
with minimal (if any) changes required to
make your program code run properly.
Turning to hardware connectivity, the
PicoMite provides 26 input/output pins
with all the usual MMBASIC functionality:
digital I/O, three analogue inputs, two serial
ports, two master SPI ports, two master
I2C ports, eight pairs of PWM channels,
1-wire connectivity, and an IR port. Next,
Micromite code
The code in this article is available
for download from the PE website.
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clock speed: the PicoMite is configurable
to run from 48MHz to 250MHz, so it is
certainly no slouch when it comes to
running program code.
Bearing in mind the PicoMite firmware
is available as a free download, and a
Raspberry Pi Pico module is available at
a ridiculously low price, you can very
quickly create an extremely powerful (yet
easy-to-use) building block that costs well
under £5.
Another big benefit of the PicoMite is that
it is compatible with many of the modules
that have specifically been made for (and
plug directly into) the Raspberry Pi Pico.
So, for example, a 2.8-inch touchscreen
module (which costs around £14 and
comes with a uSD (micro-SD) card socket)
can be plugged directly onto the PicoMite,
and with just a couple of OPTION settings,
you have the equivalent of a Micromite
BackPack, but with the added bonus of
uSD storage for programs and/or data files.
Note that there are many alternative display
modules available for the Raspberry Pi
Pico that will also work with a PicoMite,
and this is something that we will discuss
next month.
As always with MMBASIC, complex
(or expensive) development tools aren’t
required, nor are there any complicated
compiling or downloading processes to
follow. All you need to get started is a
computer with a terminal program (such as
TeraTerm), a Raspberry Pi Pico module, a
micro-USB lead (to connect the Pico to your
computer), and the MMBASIC firmware
file (a .uf2 file). So, let’s see just how easy
it is to create a PicoMite.
MMBASIC for Pico
The original MMBASIC firmware was
created by Geoff Graham a decade ago to
work with specific PIC32 microcontrollers.
Since then, Geoff has updated his firmware
with many new features and functionality.
Also, Peter Mather has assisted in pushing
USB connector
On-board
LED
Bootselection
button
Fig.1. Location of important Raspberry Pi
Pico parts used in the PicoMite firmware
loading procedure.
the capability of MMBASIC even further.
Peter is responsible for migrating MMBASIC
from the original PIC32 processors to the
more modern ARM processors (one of
which is used on the Pico – the Dual-core
ARM Cortex M0). (I wish to express my
thanks to both Geoff and Peter for their
tireless work – MMBASIC is one of the
most useful pieces of software ever created
for the electronics hobbyist.)
To begin, download the PicoMite’s
MMBASIC firmware file (PicoMiteV5.07.03.
uf2) from the July 2022 page of the PE
website. Store the file in a known location
– you will be loading it into the Pico
shortly. Next, let’s identify a few parts on
the Pico module that we will use during
the firmware loading process.
Practical Electronics | July | 2022
As soon as the .uf2 firmware file is placed
into the Pico drive, a progress bar will be
displayed indicating that the PicoMite
firmware is being installed (see Fig.3). After
just a few seconds, the Pico drive window
(and progress bar) will automatically close
to signify that the firmware has finished
loading. If you look at the on-board LED
on the Pico module, you will see that it
is now slowly flashing green, confirming
that the PicoMite firmware is up and
running. Congratulations! – you have
successfully created a PicoMite and it is
now ready for use.
Fig.2. The Pico module will appear as a USB Flash
It is worth pointing out that the only
drive when the Boot-selection button is held down
purpose of the Pico drive (initiated by
while connecting the Pico module to your computer.
holding the boot-selection button while
Note that there are two existing files on the ‘Pico
connecting the module to your computer) is
drive,’ as shown here.
to initially install the PicoMite MMBASIC
firmware (the .uf2 file). Once installed, the
firmware file will not be visible in the Pico
drive. Note too that any other files moved
into the Pico drive will simply be ignored.
To make things even easier, for any future PicoMite firmware
The Raspberry Pi Pico
updates, the PicoMite MMBASIC firmware includes the command:
The Raspberry Pi Pico was discussed in some detail in the May
UPDATE FIRMWARE which automatically brings up the Pico
2022 edition of PE. However, do not worry if you missed this
drive window (on a connected computer). This means that you
article since all we initially need to concern ourselves with are
can house the PicoMite in an enclosure without worrying about
the locations of the following parts, as shown Fig.1:
how to access the physical ‘boot-selection’ button.
n USB connector (a micro-USB type)
Now that the PicoMite is ready for use, let’s do a few tests to
n Boot-selection button (white button labelled as ‘BOOTSEL’)
ensure it is indeed working correctly. In addition, we advise you
n On-board LED (a green LED).
to download the PicoMite User Manual from the July 2022 page
of the PE website. It is an extremely useful reference, including
Loading the PicoMite firmware
descriptions of the features built into the PicoMite.
To load the PicoMite firmware onto the Pico module, you first
need to put the Pico into the ‘Bootloader mode’. To do this, simply
hold down the boot-selection button while connecting the Pico
Initial testing
module to your computer. This will result in the Pico powering
The PicoMite will behave as a serial port over USB, so your
up and appearing to the computer as an additional USB Flash
OS (operating system: Windows, macOS or Linux) will likely
drive. Your computer will automatically open a window showing
automatically detect it (especially if you’re running a recent
a ‘Pico drive’ and you will see that it contains two existing files:
version of the OS) and hence no drivers are required. However,
INFO_UF2.TXT and INDEX.HTM (see Fig.2).
if you’re not running a recent OS, or the PicoMite is not detected,
To load the PicoMite firmware into the Pico module, you copy
then please refer to page 7 of the PicoMite User Manual.
the .uf2 file downloaded previously, and paste it into the Pico
With the PicoMite still connected to your computer, launch
drive; alternatively, you can drag and drop the .uf2 file into the
your preferred terminal program (ie, TeraTerm for Windows).
Pico drive. (Note: at the time of print, the latest version of the
You will need to select the correct COM port number that
firmware file is named PicoMiteV5.07.03.uf2)
the OS has assigned to the PicoMite – it will be shown in a
list of possible COM ports as a ‘USB Serial
Device’ – see Fig.4. The baud rate can be
left set to the default (other than 1200).
On starting the connection to the correct
COM Port number, the terminal program
will automatically connect to the PicoMite.
Tap a few keys and ensure that you see
the relevant characters displayed on the
screen. Now disconnect the PicoMite, then
reconnect it, and after a second or two you
will see the PicoMite’s welcome message
displayed in the terminal program’s
window (see Fig.5).
Note that if the terminal program’s baud
rate is set to 1200 baud, then this will
automatically be detected by the PicoMite
and will result in the PicoMite switching
into the update firmware mode; hence, for
normal use, avoid using a 1200 baud rate!
With everything set up, type the following
three test commands at the command prompt
Fig.3. After placing the PicoMite’s .uf2 firmware file into the Pico drive, a progress bar
(signified by the usual ‘>’ character):
will be displayed for a few seconds showing installation progress.
Practical Electronics | July | 2022
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Fig.4. The PicoMite will appear as a ‘USB Serial Device’, and
the OS will assign it a virtual COM port number. Your terminal
program (in this case TeraTerm) needs to point to the correct
COM port – here, COM11.
and running. If you are familiar
with I/O control on a Micromite
then you will have no problem
interfacing hardware to the
PicoMite. Please do refer to
the PicoMite User Manual –
specifically pages 9, 25-27, and
Appendix A (serial comms),
Appendix B (I2C comms),
Appendix C (1-wire comms),
and Appendix D (SPI comms)
for detailed explanations and
examples, and also refer to
the Commands section (from
page 79) which details the exact
syntax for all commands.
Fig.5. This welcome message is
displayed when the PicoMite is
powered up – it will be familiar to
regular Micromite users!
I/O pin voltage
n PRINT MM.VER (to display the MMBASIC version number)
n MEMORY (to display the amount of free memory)
n PRINT PI (to display an approximation to the value of the
mathematical constant )
The result of the above should look like Fig.6 (note: MMBASIC
commands are not case sensitive).
PicoMite I/O availability
The pins that are available for connecting to the PicoMite are
summarised in Fig.7. The 26 I/O pins are shown in green and
you will see that each of these pins has a reference to a ‘GP’
number (as used by the Raspberry Pi Pico documentation), and
also a physical pin position number. For example, GP0 is pin
1, and GP28 is pin number 34. When it comes to the familiar
SETPIN command, either pin reference can be used. Hence
SETPIN 1,DOUT and SETPIN GP0,DOUT will set the same pin
to a digital output.
So, if we were to connect an LED to this pin via a current-limiting
resistor to ground, then we simply use PIN(GP0)=1 (or PIN(1)=1)
to turn the LED on, and use PIN(GP0)=0 (or PIN(1)=0) to turn
it off. This should be familiar to any Micromite user.
Now back to the on-board LED. Currently, the firmware
is using it to show a ‘heartbeat’; however, it is connected
internally to GP25 (which if you refer to Fig.7 is not actually
a physical pin made available for connection). So, we could
take control of the on-board LED if we were to reference it as
‘GP25’ – let’s now see this in action. At the command prompt,
type the following two commands:
It’s important to note that the
maximum input voltage to any
I/O pin on the Pico module is
3.6V; hence, if you are using a
5V module that needs to output
a signal to the PicoMite, then
you must use a level shifter.
Also, the maximum source or Fig.6. Three simple tests provide
sink current per pin is 12mA, reassurance that the PicoMite is
with an overall maximum total working correctly.
for the module of 50mA. Exceeding any of these limits will at
best result in eratic behaviour, and at worst you’re likely to
damage your Pico module.
Next Time
This article has shown how quick and easy it is to create a versatile
PicoMite module. Next month, we’ll move on to interfacing the
PicoMite to some of the many Raspberry Pi Pico display modules
that are available, including 2.8-inch ILI 9341 (320x240) and
3.5-inch ILI9488 (480x320) touchscreens. In addition, we will
demonstrate how to connect a much larger 9-inch SSD1963
(800x480) touchscreen, and a PS2 keyboard, to convert the
PicoMite into a powerful stand-alone ‘computer’.
Until then, stay safe, and have FUN!
Questions? Please email Phil at:
contactus<at>micromite.org
SETPIN GP25,DOUT
PIN(GP25)=1
And you will see that the onboard LED is now turned on. To
turn it off, simply type:
PIN(GP25)=0
Ok, this isn’t too impressive,
but it saved us having to hook
up a resistor and an LED! And
what if we wanted the on-board
LED to revert back to being a
heartbeat LED? Simple – just
type SETPIN GP25,HEARTBEAT
We’re not going to describe
further at this point how to use
the different types of I/O pins,
as this article is primarily to Fig.7. The 26 available I/O pins on the PicoMite are summarised here. For more specific details (and
explain how to get a PicoMite up the use of the power pins) refer to the PicoMite User Manual.
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Practical Electronics | July | 2022
