Neo said:
I am a hardware engineer and want to get aquainted with embedded
programming by working on a microcontroller development board. I would
like to buy one for myself to experiment, so are there any sites giving
good deals on the dev boards. I would like to have suggestions on what
sort of board to go for. I know a bit of C and assembly programming.
thanks in advance
Some time ago, I wanted to do a microcontroller project to become more
familiar with hardware. I decided not to go with any existing board,
but made my own design. The preliminary board may be viewed at
http://aubrey.vima.austin.tx.us
I have some experience in student labs. Many existing boards are
targeted for isolated individuals, have lots and lots of features, are a
bit expensive, and the design is closed. I designed the board so that
one working board can program the PIC in the peer board, read voltages,
accept future designs on companion boards, and students can retain them.
Olin's PIC programmer also has been demonstrated to program the board.
There are a couple of hidden items on the board. For example, the LED
array has a different value limiting resistor for each LED, so a student
can use the board to measure voltages across the drop resistor and
construct the VI curve using the board and a single probe wire. (With
student supplied software, not even a VOM should be needed.)
There is also a companion board that connects to RS-232 and tests the
cable on 8 signals. It can monitor the lines, and display the line
status when it changes. This is interesting during dial-up or an
incoming call event.
Software does 3 channel bit-bang RS-232, and when the daughter board is
configured to a pass through arrangement between a computer and a modem
using PPP, it will detect network time protocol packets and set the 64
bit firmware clock: it is on the 'net and set to UTC. (Severe
restrictions apply)
The PPP packets can also be sniffed, and dumped through the third
channel back to a monitor station.
The hardware prototype appears to be stable, and I took delivery on 21
of the boards. The one in the photo is the previous revision, where
(LOL) I placed the power jack backwards. I built up one of the final
revision, and a hardware guy in town is building another one to see if
he can spot trouble.
Some of my thoughts of what to do with the board begin on page 8 of
http://aubrey.vima.austin.tx.us/Job_Statements.pdf I wrote this
curriculum before I did any of the EAGLE work, but it has stood up
pretty well. I have demonstrated almost every item on the list in
isolation, but not a coherent final package. When I declare the
software finished, I'll make "Revision 2" of the curriculum. Work
continues.
Currently I am backing down the software to a more stable revision and
found that the previous software checkpoint was corrupt. I wanted to
add a UTC timestamp on each RS-232 line change report. I needed to do a
task swap, and the execution speed and software complexity issues looked
like they would grow a lot, but this really is beyond the original
curriculum and I came to view this as "specification creep."
As the last items in the curriculum suggest, I envision this as a
project where the design is visible and easy to change, both in hardware
and in software. For example, the "Using zener diode to protect test
circuit?" thread with Jim's crowbar and Win's 4 transistor rectifier
seem to be concepts to improve the simple zener protection that I have,
and someone else could add this if I am too pokey for their satisfaction.
I am putting together a CD for the course. This is not ready to
distribute. Most of the materials are on my computer, but the final
ready to burn CD content still requires time. Items of interest on the
CD are:
1. The complete hardware description.
a. The CadSoft eagle files that were shipped to Olimex to manufacture
the prototypes.
b. The Bill of Material ready to upload to Mouser.
c. Several photographs of the board and workbench.
c. The CADSOFT EAGLE public distribution (pending permission)
2. The complete software description
a. The MICROCHIP MPLAB assembly source.
b. The MICROCHIP MPLAB distribution (pending permission)
3. The complete curriculum.
a. Notes for 11 Saturday short courses.
b. Bill of Material to walk into empty art studio space and produce
a class for 15 students in 5 groups. (actually, 11 BOM, one for each
class ...)
4. Marketing material. (I am so lost on this section. No real progress
has been made.)
a. Concept to sell a 10 or 15 second television ad on "Andromeda"
for the short course.
b. Produced, ready to air material.
c. Web site for registration and class management.
If you feel particularly adventuresome, or like the improved access to
the design and production aspects, let me know and I'll put a bare PCB
up for auction on eBay. My address is in the .pdf file mentioned above.