Help needed for microcontroller based project.

[adam]

Hi Group,
We are a group of four B.E students studying in M.h.S.S. COE, Mumbai,
India. We writing to you to seek some help and guidance. Since this is
our first microcontroller based project, we are unaware about the
practicalities and methodologies that go into it.
In our project, we have decided to use the following:
AT89C52/AT89S52: MICROCONTROLLER
DS1307: RTC
MAX232/MAX485: LEVEL CONVERTER
AT24C1024: SERIAL EEPROM
4051B: 8:1 ANALOG MUX
IC 741/ LM324: COMPARATOR

LOGIC: 8 channels connected to the MUX, depending on which input is
enables, MUX selects it and sends it to the COMPARATOR. The second
input to comparator is a reference voltage. Comparator's output to port
1.0. Ports 1.1,1.2,1.3 as selects lines to MUX. Ports 1.4,1.5 for
intefacing with memory. Ports 3.0,3.1 as RXD and TXD. Ports 3.2,3.3,3.4
for interfacing with RTC.
Using select lines of MUX , we wish to determine which channel is
enabled.
using RTC we wish to sore the real time and pin number in EEPROM. Using
RS232C we wish to display this data on a PC.

We are facing the following queries:
1. Is our logic correct? Are all the Ic's comaptible?
2. Useful tips from your side.

We are in the stage of preparing the circuit diagram and there are many
doubts which occur. We would like you to suggest software for
preparing schematics and layout. Is there some software available which
directly converts schematic to layout? Please give names.

The next challenge is the software side. In our syllabus we have learnt
C/C++. Since you have mastered this, please guide us how to write the
programs and routines and recommend compliers, simulators and other
software related to programming. Are programs and codes available on
net? If yes, Please give the resource locations or websites.

Any help will be really encouraging and greatly appreicated by us. We
look forward for some positive response.
Last but not the least, we wish you a very happy and prosperous new
year.
Thanking you and with best regards,
Adam Mashraqui.
(on behalf of the group)

 

[MaWin]

In our project, we have decided to use the following:
AT89C52/AT89S52: MICROCONTROLLER
DS1307: RTC
MAX232/MAX485: LEVEL CONVERTER
AT24C1024: SERIAL EEPROM
4051B: 8:1 ANALOG MUX
IC 741/ LM324: COMPARATOR

741 is not suitable,
the LM324 does contain 4 of what you need only one but it will do.

Why don't you buy an ATmega128 from www.atmel.com ?
It includes 8 analog inputs, RTC and enough self programmable Flash
memory for your data, so your only additional chip would be a MAX232.
No DS1307, no AT24C1024, no 4051 MUX and no LM324.

It has too many (unused) pins ?

Ok, then think about some ATtiny (The ATtiny11 does have a comparator,
that will save you the LM324, the ATtiny24 has 8 analog inputs and a
RTC which will save the 4051 and the comparator and the DS1307 from
the parts you mentioned above) and a free C compiler like WinAVR/gcc.

 

[Spehro Pefhany]

Hi Group,
We are a group of four B.E students studying in M.h.S.S. COE, Mumbai,
India. We writing to you to seek some help and guidance. Since this is
our first microcontroller based project, we are unaware about the
practicalities and methodologies that go into it.
In our project, we have decided to use the following:
AT89C52/AT89S52: MICROCONTROLLER
DS1307: RTC
MAX232/MAX485: LEVEL CONVERTER
AT24C1024: SERIAL EEPROM
4051B: 8:1 ANALOG MUX
IC 741/ LM324: COMPARATOR

LOGIC: 8 channels connected to the MUX, depending on which input is
enables, MUX selects it and sends it to the COMPARATOR. The second
input to comparator is a reference voltage. Comparator's output to port
1.0. Ports 1.1,1.2,1.3 as selects lines to MUX. Ports 1.4,1.5 for
intefacing with memory. Ports 3.0,3.1 as RXD and TXD. Ports 3.2,3.3,3.4
for interfacing with RTC.
Using select lines of MUX , we wish to determine which channel is
enabled.
using RTC we wish to sore the real time and pin number in EEPROM. Using
RS232C we wish to display this data on a PC.

We are facing the following queries:
1. Is our logic correct? Are all the Ic's comaptible?
2. Useful tips from your side.

Sounds okay.

Suggest you use an LM339 rather than an LM324 or 741 (the latter would
require a negative supply to get common mode range that includes
ground and you'd then have to clamp the output to the rails to avoid
problems with the micro. The 339 just requires a pullup resistor (or
maybe not even that if you use a pseudo-bidirectional input).

Get something very simple like the I2C + RTC + serial communications
working first (say transmitting the current time to a PC one-way) and
then build on that.

You can write this in assembly or C (or C++ but that would not make
much sense). See what software your school has licenced for your use--
compilers and PCB CAD packages are generally not free.


Best regards,
Spehro Pefhany

 

[Rob Young]

IC 741/ LM324: COMPARATORUse a real comparator like LM339 instead of an op-amp.

Unless you need to voltage range, use 74HC4051 instead of 4051B and run
everything on +5V only. You don't say what range of input signals you want
to monitor but for a student project, just getting things to work with a
single power supply is pretty good. With a +5V only supply you can monitor
from just above 0V to just below 5V. For extra credit, explain in your
report why you can't get all the way to 0V and all the way to 5V.

If you want to use C, the SDCC compiler is free and pretty good for 8051
derivative microcontrollers. You can work under Linux or MS-DOS or Windows
(>= W98). You supply the editor. Don't bother with C++ for this. That
would be like driving tumbtacks with a sledge hammer. Assembly might be
just fine. Also WinAVR would be a good choice for the Atmel 8051
derivatives.

Search around the web for various bootloaders and debugger/monitor programs.
Google for "paulmon" and read his pages. Also look at his reference
designs.

Design everything on paper, then start from the microcontroller and work
outward, well and the power supply. Microcontroller + RS232 would be a good
pair of chips to get working first. Then add the RTC. Then add the EEPROM,
MUX and finally comparator. Heck, extra time left? Add an ADC (SPI bus,
i2c bus or parallel) too or build one using comparators (lots of extra
credit if you can build an 8-bit flash converter).

As for CAD software, there are free EDA packages, such as gEDA. CadSoft's
Eagle should have all the parts already in its library that you would need
for drawing your schematics and probably the free version may have
sufficient capacity for your PCB too. But your design sounds simple enough
that good-old wire-wrap or point-to-point wiring on perfboard should be
sufficient.

If you guys can pool your money and are able to play nice together and share
a copy, get The Art of Electronics, second Edition.

In general, Google is your friend for this project. There are tons of
examples out there, some good, some bad. Look at a few and you with some
concentration you will discover the good from the bad. If you do use
information you find during a web search, be sure to give due credit in your
report. Don't plagerize!

Have fun.

Rob

 

[Pooh Bear]

741 is not suitable,
the LM324 does contain 4 of what you need only one but it will do.

Why don't you buy an ATmega128 from www.atmel.com ?
It includes 8 analog inputs, RTC and enough self programmable Flash
memory for your data, so your only additional chip would be a MAX232.
No DS1307, no AT24C1024, no 4051 MUX and no LM324.

As a student exercise I'd have thought that interfacng the I/O would be a
useful learning process.

Graham

 

[Spehro Pefhany]

If you guys can pool your money and are able to play nice together and share
a copy, get The Art of Electronics, second Edition.

Cambridge has licenced a low-cost soft-cover edition for India and
allowed to be sold in a few nearby countries (plus Africa). I see it
listed for a paltry Rs.450, so they may as well snap up several
copies.


Best regards,
Spehro Pefhany

 

[Ken Smith]

AT89C52/AT89S52: MICROCONTROLLER
DS1307: RTC
MAX232/MAX485: LEVEL CONVERTER
AT24C1024: SERIAL EEPROM
4051B: 8:1 ANALOG MUX
IC 741/ LM324: COMPARATOR

I suggest an LT1081 for the MAX232, they are easier to get.

If you are comparing I suggest you use a comparitor like the LM339 and not
an op-amp like the LM324.

Don't trust the AT89C52's data sheet on the subject of in place
programing. If you are using that one, buy a programmer. The Philips
parts that can be programmed via the RS-232 may be a better option for
you.


Add a 1N4005 diode and an LM7805 or the like to your list so that you have
inverse protection and local regulation. It is much safer to do than rely
on an external supply being set right.

[....]

We are in the stage of preparing the circuit diagram and there are many
doubts which occur. We would like you to suggest software for
preparing schematics and layout. Is there some software available which
directly converts schematic to layout? Please give names.

I've hear people say they like Eagle for this purpose.
www.eagle.com I think.

The next challenge is the software side. In our syllabus we have learnt
C/C++. Since you have mastered this, please guide us how to write the
programs and routines and recommend compliers, simulators and other
software related to programming. Are programs and codes available on
net? If yes, Please give the resource locations or websites.

The Keil stuff is fairly good but it cost money. A few free ones are on
the web. Try google. Also feed "8051" and "free" into google.

 

[David Harmon]

On Sat, 7 Jan 2006 17:33:02 +0000 (UTC) in sci.electronics.design,
[email protected] (Ken Smith) wrote,

I've hear people say they like Eagle for this purpose.
www.eagle.com I think.

Unrelated. The Eagle software is from www.cadsoft.de

 

[Roger Hamlett]

Hi Group,
<snipped>
LOGIC: 8 channels connected to the MUX, depending on which input is
enables, MUX selects it and sends it to the COMPARATOR. The second
input to comparator is a reference voltage. Comparator's output to port
1.0. Ports 1.1,1.2,1.3 as selects lines to MUX. Ports 1.4,1.5 for
intefacing with memory. Ports 3.0,3.1 as RXD and TXD. Ports 3.2,3.3,3.4
for interfacing with RTC.
Using select lines of MUX , we wish to determine which channel is
enabled.
using RTC we wish to sore the real time and pin number in EEPROM. Using
RS232C we wish to display this data on a PC.
<snipped>

How often are you going to be writing this 'real time' , and pin number to
the EEPROM?. If it is more than a few times an hour, look at FRAM instead.
It is amazing how quickly the life of a typical EEPROM, can get used up,
if data is changing quickly.

Best Wishes

 

[Ken Smith]

How often are you going to be writing this 'real time' , and pin number to
the EEPROM?. If it is more than a few times an hour, look at FRAM instead.
It is amazing how quickly the life of a typical EEPROM, can get used up,
if data is changing quickly.

If there isn't much data, a battery backed static ram can be a good way to
go.

 

[linnix]

As a student exercise I'd have thought that interfacng the I/O would be a
useful learning process.

For commerical products, I would suggest ATmega88 and PowerPAD
(schematic to layout).

For learnings, AT89C52, transistor level shifters, op-amp comparators
(no ICs) and manual layouts (pick your gerber editor). That way, you
will be happy not to use them again.

 

[[email protected]]

We are a group of four B.E students studying in M.h.S.S. COE, Mumbai,
India. We writing to you to seek some help and guidance. Since this is

The flood of postings (and private email) I see from Indian engineering
students wanting other people to do their homework makes me very happy,
because it reminds me that quantity is not quality, and the number of
annual graduates in a field says nothing about the host country's
ability to excel in the field.

 

[[email protected]]

Suggest you use an LM339 rather than an LM324 or 741 (the latter would

You're too charitable. The original posting was way over the "do it for
us" threshold, very close to if not actually over the "here is a
collection of stuff we were told we had to use, tell us what to do with
it" line.

 

[Ken Smith]

The flood of postings (and private email) I see from Indian engineering
students wanting other people to do their homework makes me very happy,
because it reminds me that quantity is not quality, and the number of
annual graduates in a field says nothing about the host country's
ability to excel in the field.

Yes but assuming that you consider the US at least something like a
leader, you should cast your mind back to the sorts of posting we saw from
US students in the past.

You only need 1% idiots to make a lot of evidence of idoits.

 

[cbm5]

Spehro Pefhany wrote:




You're too charitable. The original posting was way over the "do it for
us" threshold, very close to if not actually over the "here is a
collection of stuff we were told we had to use, tell us what to do with
it" line.

I read the original posting and wondered what the question was. I'll
give them the benefit of the doubt and say that maybe they did pick all
their own components, but really they are at the point of "OK we have a
plan, now let's break it up and get to work." Are "all the ICs
compatible?" Give me a break...read a datasheet once in a while. No idea
what PCB CAD programs are out there, or which ones your school has
available, or whether it is possible to automatically go from schema to
layout? Not funny. Teach us how to use C++? I don't exactly have
guru-level grasp of C++, preferring to use assembly on microcontrollers,
but even I know that you don't pick up C++ on a whim. And what does "In
our syllabus we have learnt C/C++" mean, exactly? Obviously the syllabus
is not based in reality, but who made the syllabus and why does it apply?

 

[adam]

Hi Spehro Pefhany,
I will take your criticism on a positive note. You have mentioned that
datasheets can help us know about compatibility. What are the
parameters one should check to assess the compatibilty of any two IC's?
Thanks and with best regards,
Adam Mashraqui.
(on behalf of the group)

 

[Pooh Bear]

Hi Spehro Pefhany,
I will take your criticism on a positive note. You have mentioned that
datasheets can help us know about compatibility. What are the
parameters one should check to assess the compatibilty of any two IC's?

I'm disturbed that you need to ask that question if you're supposedly
studying electronics including hardware design !

Do you any ideas at all how one would decide if 2 ICs were 'compatible'.
I'm very curious.

Graham

 

[Jim Thompson]

I'm disturbed that you need to ask that question if you're supposedly
studying electronics including hardware design !

Do you any ideas at all how one would decide if 2 ICs were 'compatible'.
I'm very curious.

Graham

Put them in a room all alone ?

...Jim Thompson

 

[Spehro Pefhany]

I'm disturbed that you need to ask that question if you're supposedly
studying electronics including hardware design !

Do you any ideas at all how one would decide if 2 ICs were 'compatible'.
I'm very curious.

Graham

He also seems to have mixed up the follow-ups, as I mentioned nothing
about datasheets in this thread. cmb5 was the one who mentioned that.

You know, electronics is a really detail-oriented business, at least
on the technical end of things. I'm tempted to do a John Houseman (as
Charles W. Kingsfield Jr.) and offer them Rs. 5 apiece to call their
moms/mums.. but that wouldn't be nice.



Best regards,
Spehro Pefhany

 

[Jim Thompson]

On Mon, 09 Jan 2006 17:46:31 -0500, Spehro Pefhany

[snip]

You know, electronics is a really detail-oriented business, at least
on the technical end of things. I'm tempted to do a John Houseman (as
Charles W. Kingsfield Jr.) and offer them Rs. 5 apiece to call their
moms/mums.. but that wouldn't be nice.



Best regards,
Spehro Pefhany

"Paper Chase", one of my all-time favorites !-)

...Jim Thompson