Interfacing Microcontrollers

At Beyond Logic and Embedded Processor Control you will find interesting information on interfacing.

Real World variables are analog values, like the temperature of the Human Body. There may be Yes-No or digital events too, like the Water Level of a Tank or Door Close-Open. The former is measured by a Thermocouple and the Latter with a Proximity Switch.

These values from the sensors have to be Quickly converted to a digital form and fed to the the uC by an interrupt or cyclic polling of ports. The "How Quickly" determines How "Real Time" you system response is.

An analog value in instrumentation has to be at least 12 bit wide resolution, which is like 3-1/2, and the
The ICL7135 4-1/2 gives +/- 20,000 counts at full scale, nearly 14bit wide data. This can be interfaced both in serial and parallel data links. The serial method is used when optical isolation is required from the sensor to control circuits. If the sensor is measuring the temperature of a Transformer, an optical isolation is absolutely required.

Anantha Narayan 06:48 20-Apr-07

• UC Riverside, Serial Communication ESD lab.
• Serial MIDI Interface 80C51/80C31 Version.
• Embedded Ethernet and Internet

Embedded Process Control

Microcontrollers are versatile for process control instrumentation, The Instruments need to be small and power efficient, they have to be immune to electrically noisy environments.

When such a instrument is mounted closed to big machines, it has to be resistant to vibration failure due to harmonics. When it is used in ships or chemical industries, they need to be corrosion resistant. This makes Industrial Instruments a challenge to design, as the reliability is next only to Medical and Military instrumentation.

In applications like data loggers, scanners and PID Controllers Microcontrollers are inevitable. The analog and digital counterparts that were built years back were difficult to maintain and very big in size. With a uC a 48*48 1/16 - DIN PID Box is possible, as shown here Newport Autotune PID.

Modular Automation like PLC uses many uCs. There are Multiplexers, Analog and digital modules controlled by uC. Modern Computer based SCADA have wireless interfaces and transmitters using uC based intelligent circuits.

Anantha Narayan 06:48 20-Apr-07

• Smart Analog Process Transmitter.
• Industrial Process Measurement Control.
• Industrial Application Diagrams.
• Atmel AT89S52

80C31 and 8052 Microcontroller

8052 Microcontroller :

8048 and MCS-48 made designing with Microprocessors easy with built in I/O ports, RAM and Timer. The I/O ports for the 8085 was an external 8255. 8749 enabled users to burn and test firmware on an integrated UV Eprom.

80C51-52 which came out as the fully evolved uC had built in Serial Ports UART and more Math, better Timer-Counter and Interrupt Handling. The 'C' is for CMOS that made handheld instruments possible due to low battery usage and lesser support chips.

The Assembly Code MCS-51 set is used to program the chip. There is a 8052 Basic that can understand the Basic Language, useful for people who are not comfortable with mnemonics.

Now we have 8051 chips with EE Flash and some have a watchdog and I2C too.

Anantha Narayan 06:48 20-Apr-07

• SB Projects Knowledge Base
• 8052-Basic Microcontrollers
• NXP Microcontrollers 80C51
• Atmel - Microcontrollers - 8051
• 8051 Development Tools
• 8051 Instruction Set

Microprocessors and Microcontrollers

Analog devices like transistors and diodes lead to opamps and analog computing. This takes more parts but with fast devices can be real time. Then came Logic and Digital Circuits, here also big systems will take too many parts. A very Old hp Logic Analyzer instrument, could be HP1600A, had more than five large PCBs, Toggle Switches and numerous 74Fxx TTL Chips. I tried to revive it, it could not be fully restored.

Then came the solution the Microprocessor. Here the entire system goes into the firmware and a Hardware Tool Set in the Microprocessor made up of Logic and Math is sequentially used to perform the same operation that would require innumerable Gates in a plain hardware digital circuit. But as it performs the operations one after another, it takes time and is defined by the CPU Clock Speed.

When the External RAM and EPROM and other peripheral devices moved into the main package, MicroController were born. When more external devices merged with the MicroController. It formed a nearly complete computer, this is known as the SOC.

• 8052.com - Community, Code, How-To.
• Reads51 Learn 8051 with a IDE with C.
• Kainka Mikrocontroller - Projects, Books.
• Build your own uC Projects SBC, Projects.
• The PICList - Microchip PIC Related Archive.
• SDCC Small Device C Compiler Open Source.
• PjRc.com - 8051 Microcontroller Tools.
• ASEM-51 - two-pass macro assembler.
• Airborn design method, example projects.
• AVR Microcontroller Projects - Netherlands.

Anantha Narayan 06:48 20-Apr-07