Embedded Microcontroller Projects
Analog devices like transistors and diodes lead to opamps and analog
. This takes more parts but with fast devices, it
is 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 HP1607A, had
more than five large PCBs, Toggle Switches and numerous 74F00
Related Sections in delabs
Design Gopher -
Product Design, EDA, ASIC Design.
Hyper Embedded -
Microcontroller, SOC, FPGA, ASIC.
Microprocessor and Microcontroller chips - Solutions with AVR
and PIC are popular with Electronic Enthusiasts. TI, NXP,
STMicro and Infineon have many uC and ARM products.
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
. 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 enhnacements. Another example is the serial port or UART
in 8051, this had to be coded in the 8748.
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
(These are notes jotted down of my experience in the 90s, it
may have spelling and other errors)
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.
- Cell phones or a LAN card ASIC is ideal as volumes are
good in cell phones and for LAN cards 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