Embedded Microcontroller Projects
Analog devices like transistors and diodes lead to opamps and analog computing
. This takes more
parts but with fast devices, it is real time. Then came Logic
, here also big systems will take too many
parts. A very Old Logic Analyzer instrument, could be
HP1607A, had more than five large PCBs, Toggle Switches and
numerous 74F00 TTL Chips.
Related Sections in delabs
Design - Electronic Design Resources.
is a single-board computer designed to be both useful
and instructive in illustrating certain concepts commonly
encountered in 8052-based development. Designed to compliment
The 8051/8052 Microcontroller Book that was authored by Craig
Steiner, the webmaster of 8052.com. "
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, 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, hence the speed is
defined by the CPU Clock Speed and Bus width.
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
Now soft cores of some popular chips and new structures are
available as IP. These can be integrated in your FPGA or ASIC design
. The speed and
capabilities of a Microcontroller system depends on how
Intelligent the hardware is. Less code needs to be written, when
more standard software routines are implemented as hardware
blocks. One example is the Numeric processor 387 integrating
with uC 386 to form 486 with other enhancements. Another example
is the serial port or UART in 8051, this had to be coded in the
Digital and Embedded Systems Design
An Embedded Microcontroller or DSP system is made of Chips,
Circuits and Firmware. The digital voltage levels, speed, bus
width, fan out, power consumption are some factors that a
designer has to keep in mind. As portable and wireless gadgets
are becoming more popular, RF, Ethernet and Energy Efficient
Design aspects should be studied. Power electronics and Analog
Circuits knowledge is used around the system, all this is
integrated to make an instrument, equipment or portable
(These are notes jotted down of my experience in the 90s, it
may have spelling and other errors)
- 80C51 ports can sink more current but source very less,
hence use a 10k pull up at all the ports or outputs.
- Firmware must be developed in increments, tested in
increments, backed up in increments, must be modular
- Tristate output, High Impedance and Floating all mean the
same when it comes to IC
Inputs-Outputs. It means the pin is insulated from
rest of circuit in the IC. That means it will not influence
the node or bus it is connected to. A DMM terminals are
floating means that the hand held plastic DMM has no
electrical conductive link to earth or ground.
- You can use hyper terminal to upload code to single board
computers 80C51 like in BINARY or ASCII.
- ASICs are for large volume production, or for products
which have a long product life cycle.
- Low volume production use FPGA or CPLD, or even flash
based microcontrollers, so that all your inventory can be
reused and recycled.
- Tablets or a LAN card ASIC is ideal as volumes are good in
Laptops and for Computers the technology is matured. For
either FPGA or ASIC's you get IP Modules or Code Libraries
for many functions and applications.
- Whatever the method keep design flexible and modular for
reuse and to save cost. remember the hardware is difficult
to alter, software can be altered even at customer site,
flash has made this possible
- In the future chips may be both analog and digital
programmable with flash.
- Unused CMOS inputs should have a pull up or pull down
resistor, it should not float, or it oscillates.
- Have a decoupling capacitor 104 that is 0.1uF or 100nF
across the supply of every IC very near the IC supply pins.
- A watchdog timer should be used in every microcomputer
circuit like 8051 so that the system resets on hanging.
- The reset on a microcomputer should be applied till the
supply to it is stabilized, this will enable a clean start.
- Analog ground (opamps), digital ground (CMOS) and power
ground (relays and LED) should be separate, (linked at root)
- Pull up or pull down resistors in TTL can be 10K and in
CMOS 100K and in battery operated systems 1M.
- CMOS gates and Opamps have a output drive capability of ~
10-20mA, so when you drive a load say an LED use a series
resistor to limit the current to 5mA to 10mA.
- When the number of digital chips you use in a project goes
above 20 or 30 then it is better to use PLD or CPLD, FPGA
- Try to use same family ICs in a circuit, like only LS or
only HCT, if you mix up then you have to do a design review.
- In a industrial environment many motors, DC drives and AC
drives will be running, this will produce EMI, RFI, kickback
spikes which cause microcontroller based equipment to hang.
Use a watchdog timer for uC.
- More EMI immunity by using opto couplers for all input and
outputs, 4-20mA current signals for input and output and an
isolated wide range SMPS.