Practical_Electronics-May_2019

Make it with Micromite

Phil Boyce – hands on with the mighty PIC-powered, BASIC microcontroller

Part 4: Digital inputs and outputs

F

or those of you following this
series, by now you should have your
Micromite Keyring Computer (MKC)
communicating with a PC (using TeraTerm)
via the plug-in Development Module (DM).
If so, then you are nearly ready to begin
exploring MMBASIC and start working
through the topics discussed in the up-
coming articles. However, if you’ve not
yet had success for any reason, and you
need help, then simply drop us an email
and we will get you started.
This month, we will begin by performing
the same kind of LED test discussed in
Part 2 (when checking the MKC) to fi nish
testing the DM. This will ensure that all
the input/output (I/O) pins on the DM are
correctly connected. This is an essential
step and should not be skipped.
We will then configure a couple of
MKC options and change some settings
in TeraTerm to make the development
environment more pleasant to use.
Next, we will touch on the basics of
MMBASIC, just to ensure that we are
all aware of some fundamental concepts
regarding the Micromite and MMBASIC.
After that, the fun will begin; starting
with how to control a simple digital output
(LED), and then how to monitor a digital
input (button). If you’re thinking this
isn’t very exciting, please don’t worry

• we will quickly expand our activities
  to demonstrate just how easy it is to use
  MMBASIC to add ‘intelligence’ to these
  basic components.
  Ultimately, we will work towards our
  first mini-project, which will use the
  concepts that we’ll be covering here. That
  mini-project, which will appear in next
  month’s article, is an Electronic Dice –
  see Fig.1. Although it is just seven LEDs
  (digital outputs) and one button (digital

The first thing to do is to test your

actual test-circuit! So plug the DM into

the MKC and power it up (ensure the

two power LEDs come on). Connecting

to TeraTerm will help in a little while,

so go ahead and do that too (press the

DM reset button and ensure you see the

Micromite start up message – remember

to set baud speed to 38400, as discussed

in Part 3). Now insert the test probe into

any position on the middle 4-way header,

J8. The four points on J8 are all at 3V3, so

your test LED should turn on. If it does,

then great; however, if the test LED does

not light up then you will need to check

a few things.

Begin by ensuring the MKC and DM are

powered up (check power LEDs). Check

you have the LED in the correct orientation

input), please don’t underestimate it. My

• ‘surely there’s an app!’ – children have
  explored many board games thanks to
  the fun they have had when using this
  Electronic Dice! And it will teach you
  some very useful Micromite basics.
  We mentioned in Part 1 that the idea
  of this series is to give you exposure to
  MMBASIC and to make you aware of
  what is possible, so don’t be afraid to
  modify the hardware and code that we
  present here, after all, that is the best
  way to learn!
  It is assumed at this point that your
  MKC is successfully communicating with
  TeraTerm. If not, then please perform all
  the tests discussed in Parts 2 & 3 before
  contacting us for help.

Testing the DM

Before you continue with any of the topics

coming up, it is very important that you

successfully perform the LED test on the

input/output headers on the DM. Each of

the 19 input/output pins has two points

to test on the DM, hence 38 points in total

will need checking. These points are all

shown highlighted in Fig.2.

To perform the test, simply grab yourself

an LED and a resistor with a value between

330 Ω and 1kΩ.

Connect them as

shown in Fig.2,

either by soldering

them together, or by

using a breadboard

and some jumper

wires. Ensure that

the LED’s shorter

lead is properly and

securely inserted

into the 4-way 0V

header J7 (any of

the four points is

suitable). The test

probe can be poked

into the socket

point under test.

Fig.1. This Electronic Dice will be our

fi rst mini-project, appearing in next

month’s article.

Fig.2. Summary of the 19 I/O pin numbers and locations on the

Development Module (DM). Also shown is the simple test circuit.

2 3 4 5 6 7 9 101415161718212223242526

J10 (14-way)

J2 (6-way) J3 (6-way)

J7 J8 J9

J12 (20-way)

Reset

0V

0V 5V

0V 3V3 5V

Console3V3

Test

LED

Test

probe

470Ω

262524232221 18171615

Reset 2 3 4 5 6 7 910 14

Questions? Please email Phil at:

[email protected]