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MCU too big?

Started by abufadel August 8, 2009
Hello,
I would like to drive a two digit lcd display totaling 14 segments. The smallest msp430 that drives an lcd has 48 pins (MSP430FG477/8/9). This means there will be a lot of pins that are not connected. In addition to lcd, I would be using one a/d input pin and I2C.

Is this a good choice for what I want or can I get by with a smaller part that is not meant specifically for an LCD display..

Thank you for your input.

A

Beginning Microcontrollers with the MSP430

I think FG47x have 80 or 113 pins. And they cost $5 to $6 each.
F41x2, F42x0, and FG42x0 have 48 pins. Cost is $2 to $4 each.

--- In m..., "abufadel" wrote:
>
> Hello,
> I would like to drive a two digit lcd display totaling 14 segments. The smallest msp430 that drives an lcd has 48 pins (MSP430FG477/8/9). This means there will be a lot of pins that are not connected. In addition to lcd, I would be using one a/d input pin and I2C.
>
> Is this a good choice for what I want or can I get by with a smaller part that is not meant specifically for an LCD display..
>
> Thank you for your input.
>
> A
>
--- In m..., "old_cow_yellow" wrote:
>
> I think FG47x have 80 or 113 pins. And they cost $5 to $6 each.
> F41x2, F42x0, and FG42x0 have 48 pins. Cost is $2 to $4 each.
>

Thanks for the suggestions. Can you or anyone please explain how is it that a part can drive more LCD segments than the number of pins on the package? Does this mean that more than one segment per pin? I think I do not understand how LCD's are connected to the MCU.

Thanks again,

A

If you are that cost-conscious and can do a little experimentation, you can probably drive the LCD display with I/O directly, and some resistors, etc. Just make sure you don't leave DC on any segment / backplane combination or you'll cook the display.

Take a look at the analog (or, multi-value digital, really) signals which drive the LCD. You can probably roll-your-own for pennies. There's no magic to driving an LCD. The uC's just make it more convenient, especially when you're talking about large (many segment) displays. Yours is pretty small.

Good luck. I'd love to hear if you pulled this off. It's a good exercise, anyway.

Stuart

--- In m..., "abufadel" wrote:
>
> Hello,
> I would like to drive a two digit lcd display totaling 14 segments. The smallest msp430 that drives an lcd has 48 pins (MSP430FG477/8/9). This means there will be a lot of pins that are not connected. In addition to lcd, I would be using one a/d input pin and I2C.
>
> Is this a good choice for what I want or can I get by with a smaller part that is not meant specifically for an LCD display..
>
> Thank you for your input.
>
> A
>
For example, a LCD can have up to 144 segments divided into 4 groups. Each group of 36 segments share one common. The chip can drive one group at a time rapidly cycling through all groups. Human eyes cannot sense the flickering and will see all 144 segments. But you only need 36 pins for the segments and 4 pins for the commons.

In your case, you only need 14 segments and 1 common. The other segment pins and common pins can be used for other I/O functions.

You need to consider other features of the chip to fit your needs. But as far as LCD controller is concerned, F41x2 are as good as FG47x.

--- In m..., "abufadel" wrote:
>
> --- In m..., "old_cow_yellow" wrote:
> >
> > I think FG47x have 80 or 113 pins. And they cost $5 to $6 each.
> > F41x2, F42x0, and FG42x0 have 48 pins. Cost is $2 to $4 each.
> > Thanks for the suggestions. Can you or anyone please explain how is it that a part can drive more LCD segments than the number of pins on the package? Does this mean that more than one segment per pin? I think I do not understand how LCD's are connected to the MCU.
>
> Thanks again,
>
> A
>
For such a small LCD display most people use a STATIC LCD, which is very simple to use with any 15 general purpose I/O pins. It hooks up directly to the micro.

The 430 LCD controllers are made to drive various multiplex LCD displays with all sorts of fancy options. You don't need that.

see

http://www.ubasics.com/driving_static_lcds

if you don't like that link search for "static LCD" for more examples
--- In m..., "abufadel" wrote:
>
> Hello,
> I would like to drive a two digit lcd display totaling 14 segments. The smallest msp430 that drives an lcd has 48 pins (MSP430FG477/8/9). This means there will be a lot of pins that are not connected. In addition to lcd, I would be using one a/d input pin and I2C.
>
> Is this a good choice for what I want or can I get by with a smaller part that is not meant specifically for an LCD display..
>
> Thank you for your input.
>
> A
>
thanks for that link, Steve. That kind of article is always useful.
frank
--- On Sat, 8/8/09, bungalow_steve wrote:

From: bungalow_steve
Subject: [msp430] Re: MCU too big?
To: m...
Date: Saturday, August 8, 2009, 9:40 AM




For such a small LCD display most people use a STATIC LCD, which is very simple to use with any 15 general purpose I/O pins. It hooks up directly to the micro.

The 430 LCD controllers are made to drive various multiplex LCD displays with all sorts of fancy options. You don't need that.

see

http://www.ubasics. com/driving_ static_lcds

if you don't like that link search for "static LCD" for more examples

--- In msp430@yahoogroups. com, "abufadel" wrote:

>

> Hello,

> I would like to drive a two digit lcd display totaling 14 segments. The smallest msp430 that drives an lcd has 48 pins (MSP430FG477/ 8/9). This means there will be a lot of pins that are not connected. In addition to lcd, I would be using one a/d input pin and I2C.

>

> Is this a good choice for what I want or can I get by with a smaller part that is not meant specifically for an LCD display..

>

> Thank you for your input.

>

> A

>