PICAXE 08M2+ discussed here. PICAXE has a relatively
small following stateside; it’s more popular in France
and the UK, where it is made by Revolution Education.
Although it’s slower than an Arduino and its program
memory of 2,048 bytes is tiny, I have found it to be
more than enough for most robot projects. It’s a stand-alone chip (not a board like Arduino), so it must be
plugged into a breadboard or circuit to function.
This is the first in a series of articles based on a
course I teach using the 08M2+ in a small breadboard.
The main difference is that you’ll need to build your
own hardware, obtaining parts from a few different
sources. Think of it as a treasure hunt, with possibilities
One-Servo Wheeled Robot:
www.youtube.com/watch?v=Hf665y_FN3I
One-Servo Turtle Bot:
www.youtube.com/watch?v=yEUgA33Sdo0
Ball Bot:
www.youtube.com/watch?v=x TwfryBBo Ts
Trike Bot Figure 8:
www.youtube.com/watch?v=MPAkAzuY0Bc
Trike Bot Line Follower:
www.youtube.com/watch?v=4irMxnefgeA
Robot Arm does Towers of Hanoi:
www.youtube.com/watch?v=Og0JPJ5HQ4s
Reading a Servo Position:
www.youtube.com/watch?v=hZQx_d902uk
A PICAXE has built-in functions to control servos,
generate PWM (pulse width modulation) signals for DC
motor speed control, and read IR signals from a TV remote,
touch pads, and ultrasonic distance sensors. It has built-in
ADCs (analog-to-digital converters) for reading simple
analog sensors like photocells and thermistors. It also has
I2C communications for more
sophisticated I/O. It offers pseudo-multitasking, where (within limits)
several different programs run
simultaneously. It can run at
several different frequencies up to
32 MHz, although most robotics
commands work best at the
default speed of 4 MHz (where it
is executing several thousand
instructions per second). Future
articles in this series will get into
these functions.
A PICAXE can be
reprogrammed over 100,000
times. It always retains the last
program, which starts running as
soon as it is switched on. A
program can record data
(numbers) in permanent memory
if desired. It is connected to a PC (via a USB-to-serial
adapter) for programming or sending/receiving data, but
may be disconnected from the PC otherwise.
➤ PICAXE General
PICAXE is a family of microcontrollers which can be
programmed using a PC and USB-serial adapter. Programs
are written in PICAXE BASIC, using the free PICAXE Editor
software. There’s a newer 6.0 editor in Beta, but we’ll use
the 5. 5 editor for simplicity. We’ll use the smallest and most
popular PICAXE: the 08M2+. The tiny (~1/2” square)
08M2+ and support circuitry plug into the pocket-sized
battery-powered breadboard module shown in Figure 2. A
diagram for this minimum-parts configuration to power and
program the 08M2 is shown in Figure 3, which includes
two capacitors and two resistors.
SERVO 09.2015 49
Figure 2.
Figure 3.
