There are a wide variety of microcontrollers that can be used in robotics projects. Some of the most popular are 6811's (Miniboard and many single board computers), 80186, and PIC's. This topic engenders hot debates of the merit of one chip over the other. Therefore, the best way for you to decide is to understand your problem requirements and see which devices fit your needs. At that point, you can look at issues of support platforms, cross-compilers, cost etc to make the best decision.
Related newsgroups include:
A FAQ devoted to Microcontrollers can be found at the following: ftp://rtfm.mit.edu/pub/usenet/comp.answers/microcontroller-faq/primer The maintainer is Russ Hersch, sibit@datasrv.co.ilIn this FAQ, just brief overviews and pointers are provided for these families of microcontrollers and related devices.
Moto nows offers an evaluation kit that includes DOS and Mac compatible software, low-power design tutorial and extensive technical literature. M68EBLPIIKIT has batteries included and has 68HC11E9 microcontroller, LCD display, Moto LCD driver, RS232 line driver/receiver chips, wire-wrap area for custom work, simple development platform and development code. Includes assembler, several examples, and extra crystals. $199.11 through 4/22/94.
For a lot more detail see the 68HC11 FAQ at: ftp://rtfm.mit.edu/pub/usenet/comp.realtime/68hc11_microcontroller_FAQ The FAQ is also regularly posted to several newsgroups.
To subscribe to a listserv mailing list for 68HC11's send the following message to listserv@bobcat.etsu.edu
subscribe mc68hc11
There is also a FAQ on news:comp.sys.m68k. This FAQ covers the
Motorola M680x0 and the MC68300 series of microprocessors. There are
sections on the VME bus and PowerPC parts. Sources for software for
all Motorola products including the HC11 series is included. This
list also points to resources provided by Motorola to its customers.
Much of this FAQ is applicable to parts other than the M68K.
The 68k FAQ is available on the World Wide Web at
Contact Beall and Glenn at 800-874-4797.
It has an on-chip timer system, interrupt controller, DMA
controller, and clock generator. For DRAM operation, it also has an
integrated DRAM refresh generator. However, it has no on-chip I/O,
nor does it have any memory on-chip. There is, however, extra
circuitry for selecting external memory with a minimum of extra logic.
Can be programmed using most DOS compilers and assemblers, but
requires a linker that knows about locating code in absolute memory.
The '186 is not as accessible; it is harder to set up, the tools cost
more, and robotics and control resources have to be added externally.
The timers can be configured for PWM or pulse timing, It does,
however, run at higher speeds, have more accessible memory, and can be
hooked up to a floating-point co-processor (C187). It looks a lot
like a DOS machine. This may be important when software is run on
multiple platforms and also helps with the learning curve.
ftp://rtfm.mit.edu/pub/usenet/comp.realtime/8051_microcontroller_FAQ
It includes 8051 ftp sites, public domain langauges, commercially
available software and publications for the 8051.
UK:
CMOS field-programmable microcontrollers - PIC16/17. high performance
low cost and small package size. Large numbers are used in consumer
electronics and automotive applications, computer peripherals,
security and telecommunication applications.
A FAQ on the PIC exists and is posted regularly to the following
newsgroups: comp.realtime, comp.robotics, sci.electronics
Maintainer: Tom Kellett
Features include: timers, embedded A/D, extended instruction/data
memory, inter-processor communication and ROM, EPROM and EEPROM
memories. assemblers, linkers, loaders, libraries and source-level
debuggers are available. Digi-Key carries PIC's (See Parts Suppliers)
A simulator is available from Compuserve from the MicroChip BBS. The
simulator is SIM42000.zip and the assembler is MPA10200.zip. You do
not have to be a member of CompuServe to get to the MicroChip BBS.
Additionally, the circuit has support for Parallax's PBASIC
interpreter PICs and a serial EEPROM for storing your BASIC
program. (Sort of a giant BASIC STAMP). Note you have to buy a PBASIC
PIC ($18 from digikey or Parallax) separately. Overall my impression
is of a product, that does a lot of neat stuff but fails to be the
killer product it could have been. Consequently I'll first discuss the
weaknesses of the board before going on to the stronger aspects.
The board claims to be a 16c5x prototyper, but the manual suggests it
supports 16C71, and 16C84 parts as well. What it didn't do was add the
parts to make it an optional 16C84 programmer. Given how easy this is
I'm guessing that they just didn't think of it or had the design
"done" before they had access to 16C84 parts.
The next weakness is that while they have the EEPROM socket for BASIC
users, they don't bring the pins out the protoboard so it is not
possible to take advantage of the EEPROM in your prototype designs.
On the prototype board, +5/Gnd are available in the bus section on two
connectors but there aren't two strip connectors that you find on all
other breadboards for carrying Vcc and ground. This means that you end
up either daisy chaining your power and ground connections, or
dedicating some of the connectors on the main bread board for Vcc and
gnd.
Another area that could, in my opinion, be improved is the
availability of non-dedicated I/O devices, at the least it would be
nice to have a 4 position dip switch and 4 available LEDs that could
be used in the circuit as needed. A neat feature that would be by no
means required would be using two color LEDs to display the state of
the output as true (green), false (red), or floating (yellow).
Finally there is the issue of cost, at $195.00 this is a fairly pricey
system for what it does. Now I realize that similar systems for other
microcontrollers are similarly priced although the nearest direct
equivalent would be the Heathkit ET trainer series that were much more
oriented to learning about microcontrollers. IF I could program and
emulate PICs with it (like the Parallax tools do) in addition to using
it as a breadboard that would be wayyy cool, but I don't know how much
that would effect the price. I'd probably pay another $50 for that
improvement.
Ok, so all that grousing aside what did I like about it? I liked the
fact that I can now prototype PIC designs (hardware wise) in minutes
as opposed to hours. Prior to this device I would get a
MicroEngineering Labs PicProto board, wire up the PIC section,
wirewrap my I/O hardware or a connector that connected to my hardware,
and then start programming. If I had to redo the hardware that would
be fairly long delay. With this thing I can put the hardware on the
prototype strip or, using the 26 pin IDC connector, connect it over to
my "big" breadboard. I don't have to worry whether or not the PIC is
working and I can do a 10mhz design on a breadboard.
In terms of value for the money my guess is that I'll need to do at
least four and possibly six different designs on it before I've made
back my investment.
If it were part of a PIC seminar, it would be a wonderful teaching tool.
There is a BASIC STAMP Mailing List (NOT a newsgroup)
The significance of the 'D' in L293D is that it is diode protected.
There is a reverse biased diode that shunts the reverse EMF from a
motor to the V+ supply. The L293B doesn't have this diode so it must
be provided externally.
Although there are reports of shortages of the 68HC11, presumably
because of large customers, here is one vendor who is reported to have
significant stock:
MC68HC11A1 - $2.50 each.
MC68HC11E1 - $3.00 each.
MC68HC11E1 - $3.00 each. ( This is a 12Mhz version.)
If you order over $20 the shipping is free. They also take VISA.
[18.2] Motorola 683xx
The 683xx family from Moto are highly integrated CPU's.
Several have onboard RAM (eg, up to 2K), none have on-board ROM, but
they do have timers, software programmable chip selects, etc, making
it possible to build very small but complete systems.
[18.3] Intel 80C186
An 80C186 is a evolution from the 8086. It is an embedded
processor sold by Intel, and has the same instruction set as the 8086,
with the additional "real-mode" instructions of the 286. It has the
same 16-bit data and 20-bit address bus structure of the 8086. The
80C188 is an 8-bit data bus version, just like the 8088 (of PC and PC/XT
fame). For embedded systems, it is much easier to use than the 8086.
[18.4] Intel 8051
A typical 8051 contains:
The 8051 and varients are now sourced by more than a half-dozen
companies including Intel, AMD, Dallas, Signetics, Siemans and others.
The 8051 FAQ can be found at:
[18.5] Intel 8096
It is 16 bit, many registers, internal RAM, the usual compliment of
on-board peripherals (serial, A/D, pwm, timer/counters, etc)
[18.6] Microchip PIC16/17
Vendors of PIC boards:
These are from reviews by Chuck McManis The PICProto Dual - $14.95 US
Is similar except it has pads for 1 18 pin PIC and 1 24 pin
(or another 18 pin) PIC. It is 3" x 3" and shares all of the same
properties of the PICproto 18 with respect to setting up crystal or RC
timing for the PICs. It has pads for 1 DB connector that is 25 pins
or less. It adds about 50% more prototyping pads so you can put two
or three more chips on it. The nice thing about this one is that one
PIC can do asynchronous things like be a serial interface while the
other provides I/O pins and monitoring functions.
PIC Prototype-1 - $195.00 from Digikey
This gizmo is made by Depew Engineering (depew@maroon.tc.umn.edu) and
is sold by Digikey and Parallax and possibly others. It is a
breadboarding system for testing out PIC designs. If you have a
Digikey catalog you can look at the picture there, but it is basically
a circuit board with a 28/18pin ZIF socket in the upper left corner, a
9 pin DB-9 connector that is attached to a MAX232 chip to provide
RS-232 levels and a 25 pin DB-25 connector at the top center which is
wired as a "parallel" port like you might find on a PC. Continuing
across the top, now in the right hand corner there is a coaxial power
plug and switch. Along the right side are five 7 segment displays that
are permanently wired to display the value of PORTA, PORTB, and PORTC
(when available) in hex notation, along the lower right are a set of
dip switches for setting the clock rate (500Khz - 32 Mhz in 32Khz
increments). Along the bottom edge are green LEDs showing the state of
all the PORT pins (in binary :-)) and taking up roughly 45% of the
circuit board is a solderless breadboard section. The solderless
breadboard has two primary sections, an upper bus section containing
connectors attached to all of the PIC pins and some useful pins on the
board (like inputs to the MAX chip and outputs from it), and a lower
section which is a standard breadboard with two rows of 5 pin
connectors spaced .3" apart.
-Chuck McManis
[18.7] Parallax BASIC Stamp
The Stamp is a 1x2" (2.5x5cm) computer that runs BASIC
programs written on a PC. 8 I/O lines which can be used for serial
communications, potentiometer inputs, pulse measurement, switches,
speaker drivers etc. Usually you'll have to add no more than a
resistor or capacitor at most. A BASIC editor on the PC converts
instructions into token that are downloaded to the Stamp via a
3-conductor cable and stored in EEPROM. Whenever the Stamp is powered
up, the on-board interpreter runs the program. Battery clips are built
in for a 9V battery (Stamp has 5V supply built in.) and the Stamp has
a small prototyping area as well. From Digikey the Development Kit
(including a Stamp) is $139, and a Stamp is $39.
[18.8] National Semiconductor LM628/629
Small motor control chip. Does PWM for motion control at a very low
cost. A couple of H-bridges on the outputs. Good reference for using
the 628/9 for motion control is in: Closing the Loop on DC Motor
Control by Tom Dahlin and Don Krantz The Computer Applications
Journal, Issue #28 Aug/Sept, 1992
[18.9] Hewlett-Packard HCTL 1000, 2000
HP's motor and encoder interface chips. Widely used and widely available.
[18.10] Motor Drivers
This section primarily addresses chip-level devices for
controlling motors. See [10.2.5]
Controllers for more complete motion controller products.
Allegro
ILC Data Device Corporation (DDC)
SGS-Thomson
The L293D, motor driver on a chip, is an SGS-Thomson part and is
second sourced by Unitrode. In spite of its utility it is not readily
available in small quantities. This part is a dual full H-bridge that
can drive motors up to 0.6A.National Semiconductor
National has an LM18293 which they say is a cross for an L293B. The
price should $4.00 or less and they need the external diodes. A
replacement for the D part is the Texas Instruments 754410 which
actually has a bit better current capacity (1A vs .6A) this latter
part is available from Arrow electronics in the US.Unitrode
An alternative part is the UDN2998. This is a 3A bridge in an
inline package, it is limited to motor supplies greater than 10V. You
can also build your own H-bridge out of either bipolar chips or
MOSFETs.
Last-Modified: Sun Aug 11 08:53:25 1996
Kevin Dowling <nivek@cmu.edu>