MC9S08QG8 SPI Interface to 3 1/2 Dight Display

[JohnB3]

Hi Group,

I am designing a motor control application using the MC9S08QG8 utializing the SPI Interface.

Can someone recommed a 3 1/2 Digit LCD display component with an SPI interface?

Is there some example code available?

Thanks

John

[airbusboy20]

Might be worth having a look at New Japan Radio's range of SPI LCD drivers:-

http://www.njr.com/index4.html

Although they don't actually incorporate an LCD, they should drive a standard off the shelf part OK...

Gary

[JohnB3]

Thanks, Gary.  I had not run across this source before.

[MidonDesign]

John,

Consider also the MC14499 serial to 7 segment driver.  It isn't SPI per se, but it can be easily adapted for use with an SPI interface.

Mitch

[RogerSchaefer]

Check out my project

http://www.rasmicro.com/DS18B20.htm

for a hardware and software example of exactly this.

Roger Schaefer

[Alban]

Hello Roger,

http://www.rasmicro.com/

is really a great resource for the electronician. Thank you for sharing this URL

Cheers,
Alban.


EDIT: link corrected + signature forgotten


Message Edited by Alban on 2007-09-28 08:06 PM

[JohnB3]

Hi Roger,

This is what I was looking for, but I really appreciate the brainstorming from several others who responded.  It served to open my eyes to several posibilities in directions I had never even thought about.

Thanks.

John

[JohnB3]

Thanks, Mitch.

I'll check it out.

John

[JohnB3]

This display will be used during development to didplay various parameters and status information.  I am using SPI interface for quad D/A and quad A/D converters to read & control environmental parameters.  The SPI serial bus allows for smaller packages in a seriously space cramped application and still allows for fast (enough) data communication for proper control.

I will look at the other microcintroller you suggested for other applications, but I would really like to be able to locate a SPI interface display component for the development.

Thanks

John

[bigmac]

Hello John,

Another approach is to use a shift register device (e.g. 74HC595 or 74HC164) to provide the interface between the SPI, and an alphanumeric LCD display operating in 4-bit mode.  If the display is required during development and test only, I assume the shift register and display would be part of a "test jig".

Each shift register type would require a slightly different approach, but you will need one further output signal from the MCU, in addition to the three signals associated with the SPI bus.

Yet another approach would be to incorporate an additional MCU within the test jig, to provide the SPI interface.  This will eliminate much of the additional code, required for the LCD communications and formatting, from the QG8 device within the equipment.

Regards,

Mac

[johnbeaty]

This is great.  It is about at the level I need.  This device would be used to debug the development - not part of the final design.  I plan to send out 3 digit status and "location" within the program execution, so just a simple set of 3 shift registers and 3 bytes shifted out to drive segments to create the numbers should show the status.  Later I may find a use for a small graphics display if I can find a driver IC that will talk SPI.

Thanks for the suggestion.

John

[JohnB3]

Hi Mac,

Thanks for the suggestions.  Both are viable.  The shift register suggestion I actually had thought of but put aside until I had heard from folks who might be more familiar with what is out there to use. 

The second processor I had not thought of.  As you said, this is just for development, I have a spare QG8, and if nothing else shows up at a reasonable price, that may be the way to go.

Thanks for the suggestions.

John

[peg]

Hi John,

If you add a display to the existing SPI bus then you probably need another CS from the QG.

If you have a spare pin on the QG then can't you free up the TxD pin and implement an output only RS232 to a dumb terminal emulator on a PC. If this is possible it would be easier within the QG and open up far more possibilities for output over a 3.5 digit display.

Just a thought!

[JohnB3]

Hi Peg,

WOW!  Now that is a quantem leap over where my '8-bit-single-board-computer' level brain operates. 

I need to go back & look at the design again.  The SPI requires certain dedicated pins and I need to use it to talk to the SPI A/D & D/A converters, but I will look at it & see if I have enough brain cells left to grasp how to set up your suggestion.  It opens up the possibilities of vastly improved status monitoring, even grapging the ramp, etc.

Thanks

John

[Encoder]

Dear John,

what do you intend for 3 1/2 digit display? It's only a numeric display? How big must it be and which technology?

I think that any SPI interfaced display is a quite exotic one: i.e. very few models and rather costly.

Have you considered using a standard low-cost alphanumeric display? There are hundreds of models to chose from and many are surprisingly cheap, with the advantage of permitting display of a full text string in addition to simple numbers.

You can use a nibble driver approach needing only 7 gp I/O lines, i.e. less than 1 full 8-bit port with a moderate software increased difficulty or a full byte driver, with a simpler approach and 11 I/O lines needed.

If your 9S08QG has not enough lines (very easy even with the nibble driver), I suggest to change it in favour of a slightly bigger MCU like an 9S08GT8A, with plenty of I/O lines and a budget price of 1.40$ vs. 1.13$ of the smaller one. The added lines may prove useful to you or not, but the price is very small. And a simple 14 or 16 wires flat cable is all you will need to connect the display to the controller board.

Regards,

Encoder