Microcontroller

A microcontroller (also MCU or µC) is a computer-on-a-chip, containing a processor, memory, and input/output functions. It is a microprocessor emphasizing high integration, in contrast to a general-purpose microprocessor (the kind used in a PC). In addition to the usual arithmetic and logic elements of a general purpose microprocessor, the microcontroller integrates additional elements such as read-write memory for data storage, read-only memory for program storage, EEPROM for permanent data storage, peripheral devices, and input/output interfaces. At clock speeds of as little as a few MHz or even lower, microcontrollers often operate at very low speed compared to modern day microprocessors, but this is adequate for typical applications. They consume relatively little power (milliwatts), and will generally have the ability to sleep while waiting for an interesting peripheral event such as a button press to wake them up again to do something. Power consumption while sleeping may be just nanowatts, making them ideal for low power and long lasting battery applications.

Microcontrollers are frequently used in automatically controlled products and devices, such as automobile engine control systems, remote controls, office machines, appliances, power tools, and toys. By reducing the size, cost, and power consumption compared to a design using a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to electronically control many more processes.



[edit] Platforms from Parallax, Inc.
Parallax produce the BASIC Stamp. These are Microchip PIC microcontrollers programmed with an interpreter that processes a program stored in an external EEPROM. Several different modules are available of varying processing speeds, RAM, and EEPROM sizes. The BASIC Stamp is used by Parallax as a platform for introductory programming and robotic kits.

The Parallax SX line of microcontrollers, formerly made by Ubicom, are 8-bit RISC microcontrollers (using a 12-bit instruction word) which have an unusually high speed, up to 75 MHz (75 MIPS), and a high degree of flexibility. They include up to 4096 12-bit words of Flash memory and up to 262 bytes of random access memory, an eight bit counter and other support logic. They are especially geared toward the emulation of I/O hardware in software, which makes them very flexible. SX-Key is Parallax's development tool for the SX line, supporting every SX chip commercially available. Using free SX-Key software (Assembly language), or the SX/B Compiler (BASIC-style language) from Parallax, the SX-Key programming tool can program SX chips in-system and perform in-circuit source-level debugging.

The Propeller is a multi-core microcontroller developed by Parallax, Inc. The currently released version features eight 32 bit cores, each operating independently at 80MHz, and 32 I/O pins. Most instructions require 4 clock cycles, so each core runs at 20 MIPS. Hub instructions, used to access the 8192 32 bit words of system memory and to communicate between cores, require between 7 and 22 clock cycles. There are also 512 32 bit words of memory on each core, which can be used to avoid using the slower system memory instructions. It can be programmed both in assembly language and a custom interpreted language named SPIN.





The BASIC Stamp is a microcontroller with a small, specialized BASIC interpreter (PBASIC) built into ROM. It is made by Parallax, Inc. and has been quite popular with electronics hobbyists since the early 1990s due to its low threshold of learning and ease of use (due to its simple BASIC language).

Although the BASIC Stamp has the form of a DIP chip, it is in fact a small Printed Circuit Board that contains the essential elements of a microprocessor system:

A Microcontroller containing the CPU, a built in ROM containing the BASIC interpreter, and various peripherals
Memory (a serial EEPROM)
A clock
A power supply
External input and output
PBASIC, the BASIC Stamp language, incorporates common microcontroller functions, including PWM, serial communications, I²C and 1-Wire communications, communications with common LCD driver circuits, hobby servo pulse trains, pseudo-sine wave frequencies, and the ability to time an RC circuit which may be used to detect an analog value.

The end result is that a hobbyist can connect a 9V battery to a BASIC Stamp and have a complete system. A connection to a PC allows the programmer to download software to the BASIC Stamp, which is stored in the onboard memory device. This memory stays programmed until it is erased and reprogrammed (the memory remains intact even when the power is removed).

There are currently four variants of the interpreter, BASIC Stamp 1, BASIC Stamp 2, the Javelin Stamp and the Spin Stamp. The Basic Stamp 2 variant has seven sub-variants:

BS1
BS2
BS2e
BS2sx
BS2p24
BS2p40
BS2pe
BS2px
These sub-variants feature more memory, faster execution speed, additional specialized PBASIC commands, extra I/O pins, etc, in comparison to the original BS2 model. While the BS1 and BS2 use a PIC, the remaining BASIC Stamp 2 variants use an SX processor.

The third variant is the Javelin Stamp. This module uses Sun Microsystems' Java programming language instead of Parallax's PBASIC.

The fourth variant is the Spin Stamp. The module is based on the Parallax Propeller and therefore uses the SPIN programming language instead of PBASIC.

Many companies now make virtual "clones" of the BASIC Stamp with additional features, such as faster execution, Analog-to-digital converters and hardware based PWM which can run in the background. However, many use the same pin out as the BASIC Stamp, to allow BASIC Stamp users to plug in their products in a design that already uses the BASIC Stamp