Project Question

[mn_vette]

I'm looking to build a small project that consist of your typical quiz buzzer circuit with the addition of 4 or 5 timers.  I have built this project before and its just a mess to make on a proto board.  So I'm looking for a micro controller to help limit that. 

Here is the basic circuit, just half of what I need.

http://www.zen22142.zen.co.uk/Circuits/Misc/quiz.htm

The micro would need 25 general IO for this porject, so I'm looking at the MC9S08GT8A in the 40pin dip.  I'm looking to use the internal clock, 8MHz is faster than it needs to be.  I hope this clock will be accurate enough for the timers, 5 sec, 30 sec, 60 sec, and 180 sec. 

From my preliminary check of the data sheet, this should work just fine.  But I'm hoping that the experts may see something that I'm missing.

Also can you give me an overview of what I would need to do programming to this micro?  As always cost is of the utmost importance.  Thanks.

[irob]

I like the part you've chosen.  It's a nice family with the internal hardware emulator, which is great for code development.  You can step through your code on the actual target board itself. Very nice feature.

As for programmers, they aren't cheap.  We use P&E Micro's line of programmers.  We have the USB Multilink which is quite nice.  It's $100, but the software for the 9S08 family is not free.  It's $169.

But since cost is your primary concern, have a look at the Open Source BDM on this forum.  All the project plans, drawings, software, CAM are available for free.  Of course, you have to build it to use it. 

[irob]

Say, here's a cheaper solution than the P&E route and of course quicker solution than building an OSBDM yourself.  $40 gets you a programmer that your Freescale v6 CodeWarrior will recognize.  It's based on the OSBDM design.  And the dev is one of the contributors here.

[mn_vette]

Thanks for the heads up on the programmers.  I'm definately going to look into that $40 one. 

Quick question on the MC9S08GT8A.  In the 42 pin version it has 5 high current output pins(20mA).  But I need to run 9 LED's.  The other output pins have a max of 2mA each.  Is there a simple way to get around this to get enough current to run a decently bright LED?  I guess I can gang two pins together, but that only gets me 4mA, typical LED's take 10-20 don't they?  Or maybe I'm just not farmiliar enough with the 3V LED's 

[irob]

Just make yourself a current sinking LED driver with a transistor hooked to those port pins.  Something like this.

[mn_vette]

Since I need a bunch of them I wonder if its better for me to just get a quad or gate and run the LED's off of that.  If only this chip had a few more of those high current outputs, but things are never as easy as they seem are they?

[irob]

Like this? 8-channel, 500mA, DIP-18, darlington NPN array, P/N: TD62083APG.  In stock @ Digikey, cheapest array that size they have.

--
Alban Edit: correction of erroneous link.


Message Edited by Alban on 2007-10-10 07:28 AM

[mn_vette]

That's exactly what I need.  I think 500mA is a bit overkill for running some LED's, but it will definately work.  Thanks.

Now I just need to start working on the code and compiling a list of components before I order. 

[irob]

---

mn_vette wrote:

That's exactly what I need.  I think 500mA is a bit overkill for running some LED's, but it will definately work.

---

Well, I was only searching for items in stock and were least expensive.  You're right, half an amp is excessive.  But cheap excessive!

---

mn_vette wrote:

The typical proto boards and what not spaced at 0.1".  However, after looking at the MC9S08GT8A datasheet it says that the pins are spaced on a 0.07" spacing.  Is there some kind of a converter socket that I can get to place this on a typical board?  Or do I have to flip it and dead bug the micro to the board?

---

Why not get the DIP package?  P/N: MC9S08GT8ACBE, Mouser has stock, $2.63

Message Edited by irob on 2007-10-11 03:26 PM

[mn_vette]

That's the exact part I have.  Unfortunately its not a dip package its a SDIP package.  So the pins are spaced 0.07" apart.  I managed to get it onto a bread board by bending most of the pins out of the way and doing a quick solder to the ones I need. 

Everything is up and going.  Now I just need to figure out how to make my project and flash it to the chip.  Unfortunately it can't find a MCU_init_fv something or other.  I'm probably forgetting to push a button to build something.  Off to the search to see what I can come up with. 

[irob]

Oh man, that's a bummer!  Well, here's a socket adapter for $175!  I checked Digi-Key and they have some 2mm grid proto boards, but no 70mil.  Why in the world does Freescale make a part with this pitch?!

[mn_vette]

Well, after reading way too many data sheets I think I'm going to switch over to the MC908JL3ECPE.  Its a normal 28pin DIP package, has 10 LED outputs, and just enough IO for what I need.  However, it does require an external oscillator, but no LED driver chip. 

I've got two quick questions.

1.) Is the MC908JL3E the same thing as the MC68HC908JL3E?  According to Freescale one is the replacement part for the other and they link back to the same datasheet.  But are there any hidden changes or anything like that? 

2.) How do you program this device.  It doesn't have a back ground debug pin so I'm guessing there is some other tool to use.  The data sheet has some kind of code instructions, but it doesn't say how to hook up the external pins to get the thing to be programmed the first time. 

Message Edited by mn_vette on 2007-10-15 02:05 PM

[Alban]

Hello,

1- To see changes, you can look at the errata sheet. The part number have been compressed lately.

2- It is in the datasheet, at the Development Support chapter. You use a RS232 port with level translation to 5V (like MAX232) to program the MCU.

Regards,
Alban.

[mn_vette]

There is no Development chapter in the data sheet.  I did manage to find the MON chapter though. 

Building the circuit in the datasheed does not appear to be that difficult.  But is there any additional software that I would need?  Or does the MON08 interface connection in code warrior take care of that for me?

[Alban]

Yes, CodeWarrior handles all types of MON08 connections natively.
I almost never used anything fancy to program HC908.

Alban.

[mn_vette]

Thanks for the reply.  It sounds alot nicer to make a $5 programmer and use the free software for the HC908 stuff rather than buying a $50-200 programmer for the HS08 chips.  I guess I should have started looking there in the first place.

[Alban]

I can advise you a cheap tool for S08.
The OSBDM08 was created to be a cheap option for non-production purposes.

You can find different versions on the version table post I wrote:
http://forums.freescale.com/freescale/board/message?board.id=OSBDM08&message.id=212

Debugging is easier with S08 than with HC08...

Glad I could be of assistance.
Cheers,
Alban.

[mn_vette]

Ok, here's another dumb question for you guys.  The typical proto boards and what not spaced at 0.1".  However, after looking at the MC9S08GT8A datasheet it says that the pins are spaced on a 0.07" spacing.  Is there some kind of a converter socket that I can get to place this on a typical board?  Or do I have to flip it and dead bug the micro to the board?

[PeterHouse]

How much time do you have?

A consultant can get it done quickest while you could learn it and build something yourself.

Consultant = Short Time and High Cost
Yourself = Long Time and Low Cost

You can probably mix this approach by hiring a consultant to stear you in the right direction and help with processor selection, peripheral selection, coding and hardware design depending on your skill and existing experience with software and hardware.

Good Luck,

Peter House

[mn_vette]

I have some time.  This isn't something that needs to be done yesterday.  As far as hiring a consultant goes, defintatly not.  Price is my number one concern with this project.  I'm hoping that the micro will cost less than all of the components to do it discretely. 

I know the big cost setback will be the programmer, how much do the basic ones run?  But if I can spread the cost over a few units, it would definatley be worth it in ease of assembly. 

As far as the programming goes, I should be able to handle it.  Given that the code will be mostly digital logic, it should not be too difficult to do.  The timers may take a bit to figure out, but I have some friends that do this programming professionally if I need to get bailed out.