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MCU/uC Microcontrollers

While reviewing items for our HomeNetwork (Home-Automation) project we reviewed several microcontrollers (aka MCU or uC). Here some infos we digged out.

1. What is a MCU?
2. PIC MCU
3. AVR 8 bit RISC
4. MCU Networking
5. MCU Resources

A computer is usually build by several components, CPU, Memory, peripherial controllers and so forth and all together make up a machine, a computer. A CPU (aka microprocessor) itself can't do anything. A microcontroller usually integrates a minimal functionality on one or few chips. As of 2001 several one-chip microcontrollers are available with Flash memory which are programmable serial via PC, this means, you get a micro-computer literally in one chip plus few electronic components like quartz and 1-2 capacitors.

MCU Lab 2. PIC MCU

The PIC serie is developed by Microchip.Com for quite a while has many tools and application notes and implementation have been done. Among hobby engineers one chip made its way: PIC-16F84. Its features:

• 18 pin
• 1K (14bit) Flash memory
• 13 I/O
• 8 bit counter/timer
• cost ~$8-$10 (4/10 MHz versions)

PIC-16F628 is pin-compatible with real UART and 2K Flash memory, for other PIC microcontrollers (vast selection) visit

Microchip.Com PIC manufacturer site

Programmer

NOPPP ("No-Parts Programmer") Support for PIC16C84, PIC16F83, and PIC16F84(A), schematics and infos, via parallel port (minimal components required 'no-parts') No Parts PIC Programmer Linux Same as NOPPP plus support for PIC-16X83/4

Compilers

GCC Man Page GCC natively support PIC cross-compiler

Resources

Fortunately a lot resources are available, best use google to search for application notes, examples, and experiences, or look here: Microchip.Com Start here first, especially the Application Notes are worthwhile and tell a lot WebRing: PICmicro Good point to start

MCU Lab 3. AVR 8 bit RISC

Another popular MCU has been the AVR from Atmel.Com.

• AT-90C2323: 8pin, 2K Flash, 3 I/O, cost ~$8
• AT-90C1200: 20pin, 1K Flash, 15 I/O, PWM, cost ~$8
• AT-90C2313: 20pin, 2K Flash, 15 I/O, UART, PWM, cost ~$10
• AT-90C4433: 28pin, 4K Flash, 20 I/O, 6x A/D 10bit, UART, PWM, cost ~$15
• AT-90C8515: 40pin, 8K Flash, 32 I/O, UART, PWM, cost ~$20
• just to list a few ...

PWM (Pulse Width Modulation) allows D/A conversion indirectly, all are operational at 0-8/10 MHz, 2.7-6/8V (check datasheets).

Atmel.Com Manufactured site

Programmers

AVR-1 Programmer for Linux Driver for the STK-200 board (sold by Atmel)

Misc Infos

The AVR 8 bit RISC are considered 'low-end' MCUs, and there has been reliability issues as well: Considering the AVR? Read This..., so "Brown-Out" (voltage going below suggested operation range) seems common problem compromising Flash memory on MCU despite having 'detectors' build-in, many real-life applications suggest external "Brown-out" circuits, especially in case of AVR recommended. Another problem with AVRs has been availability, check with your local store; here in Switzerland the major electronic distributor has them.

Compilers

GNU Tools & Atmel AVR MCUs Download infos (patches for GCC) AVR Tools for Linux AVR GCC infos & mailing-list

Resources

Atmel.Com Start here first, get the Application Notes which show what can be done with the MCUs AVRFreaks.Net Good starting point AVR Embedded MCU Resources Extremely useful collection of links related to AVR MCUs

MCU Lab 4. MCU Networking

One of the next considerations are how to network MCUs together? Most Application-Notes describe various microcontroller networking approaches:

LIN

LIN (Local Interconnect Network), short-range, 20kbps, master/slave, 2 wires.

CANbus

CAN (Control Area Network), 120kbps - 1Mbps, (100m 500kbps, 200m 250kbps,.. 6km 10kbps), 4 wires. CAN Main site Philips.Com: CAN More infos

I2C

I2C (Philips): 2 signals + ground, 100kbps (400kbps). Voxel Project: I2C for Linux.

1-Wire

1-Wire formerly known as MicroLAN (Dallas Semi.), 1-wire (signal+ground), 115.2kbps

RS-232 / RS-485

RS-232 with UART (or emulated UART), point-to-point, up-to 1Mbps, 4 wires (2-25 wires). RS-485 with internal/external UART, multi-drop/point, up-to 10Mbps, 2 wires. RS-485.Com: Specifications RS-232, RS-485 and RS-422 Overview

Other Approaches

National Semi: Microwire Motorola: SPI

TCP/IP for MCUs

uC/IP TCP/IP for MCU/uC's (not yet much, May 2001) iPic World's tinyest web-server Thin Server Overview of thin servers based on MCU or small boards EthernetEmbedded.Com Embedded ethernet (small board)

MCU Lab 5. MCU Resources

EPanorama: Microcontrollers Good starting point

Microcontroller.Com Another resource site

Dontronics.Com Australian company developing SIMM-Stick with PIC/AVR

                                                                                                                                   

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