ADVANCED TECHNIQUES FOR DESIGN ENGINEERS
■ BY FRED EADY
Pedaling the STC12C5A6OS2
The multiple variants of the original 8051 core are like a bunch of bicycles.
Once you learn to ride one, you can ride them all. That’s a good thing because
this time around, we’re going to put our feet on the pedals of yet another
version of the good old 8051 microcycle. The STC12C5A60S2 we are about to
discuss is manufactured by STC Microcontroller and is an enhanced version
of the 80C51. The 8051 microcontroller needs no introduction. So, let’s get
down to moving some electrons with the STC12C5A60S2.
The base STC12C5A60S2 (STC12 for short) hardware
we will be working with exists in the form of an STC51
EVK-Pro professional evaluation kit which is the object of
affection in Photo 1. As you can see, the EVK-Pro eval kit
is a seriously busy electronic package. In addition to the
ZIF-socketed STC12 microcontroller, the kit visuals include
two banks of four-digit seven-segment LED displays, a
color LCD module, an LED matrix module, a 16 x 2 LCD,
and an eight-bit row of variously colored super bright
If you have a thing for buttons, the STC51 EVK-Pro kit
sports a 16-button matrix arranged as a 4 x 4 keypad and
three large individually addressed momentary pushbuttons
that will delight your index fingers. If that’s not enough for
you, a 21-button IrDA remote module and supporting
HS0038 IrDA sensor are also part of the package.
Chances are this ain’t your first microcontroller rodeo.
So, you already realize that embedded devices tend to
lean towards monitoring and control applications. Well,
the STC51 kit is no exception. On the monitoring side of
the embedded arena, an eight-bit I2C-equipped analog-to-digital/digital-to-analog converter in the guise of a
PCF8591 keeps watch over a potentiometer, photoresistor,
and thermistor. If you have embedded monitoring ideas of
your own, you can override the aforementioned variable
resistance devices attached to the PCF8591 and wire your
desired array of sensors into the PCF8591’s analog inputs.
In addition to the PCF8591/thermistor combination, the
STC51 eval kit offers an alternate means of temperature
sensing with the inclusion of an on-board MAXIM
DS18B20 1-Wire digital thermometer.
The embedded control components at the other side
of the embedded arena are under the control of a high
current ULN2003 Darlington array. Four of the seven 500
mA Darlington pairs terminate at a five-pin connector that
is designed to provide drive for the coils of the stepper
motor that is an integral part of the evaluation kit. A
separate Darlington pair provides drive for the five volt
■ PHOTO 1. This is one busy piece of electronic hardware.
Like everything complex, it becomes simple when digested
in smaller portions.