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Cannonadek

My First Question

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This question may be better suited for the projects forum, but I have nothing to show (yet). Before I spend many nights trying to figure this out, I want to know if it is even possible. There are many computations I have top preform on a daily. These are easy enough, but I'm lazy so I want to make them easier. In the end I would like to be able to do three things. 1. Get user input form a keypad. 2. Preform the calculations. 3. Display both the user input and the finished calculations on a LCD. Power consumption will be a concern later down the line, that's one of the reasons I picked the Launchpad. Thanks in advance for the help.

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Hmm... LCD and a Keypad, both are pin hungry. However with tricks you can use bot together.

 

- How many keys do you need, a full keypad or only user interface buttons? A keypad normally needs 4 rows and 4 columns - that's 8 pins.

- How comples are your calculations - Do you need answers immediately or a few ms delay is ok?

- Floating point is a big no-no as we are limited on memoryy.

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- How many keys do you need, a full keypad or only user interface buttons? A keypad normally needs 4 rows and 4 columns - that's 8 pins.

- How comples are your calculations - Do you need answers immediately or a few ms delay is ok?

- Floating point is a big no-no as we are limited on memoryy.

 

1. I was thinking that I need 12 keys (0-9, enter, and backup) on the keypad

2. The equations are not that complicated. They can be done on the most basic scientific calculator. There is one square root function.

3. A delay would be acceptable even if it was a few full seconds long. I wrote a program for my TI-86 to due the same thing, but at $100 dollars each they get expensive when you drop them in a puddle of mud. Plus I could try and make this almost bullet proof if I need to :D .

 

As for the number of pins and memory requirements can I use two or three MSP chips together? For example one chip to run the keypad, then relay the inputs to a second chip that does the math and then displays it?

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As for the number of pins and memory requirements can I use two or three MSP chips together? For example one chip to run the keypad, then relay the inputs to a second chip that does the math and then displays it?

Breaking up the control and math is a good idea, for 12 keys i think you could multiplex 3 rows of four keys to cut down on pin count too (3 control pins - with 4 data pins = 7 pins total).

 

 

MSP430s could communicate with each other by using SPI or I2C protocols, and both are built in to the uart.

 

 

I think this would be an intersting project, I hope to see more on it :)

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I haven't thought about the keypad or the LCD yet, I wanted to see if I could even program one of these chips first. As for the LCD I was looking at serial ones only because of the pin requirements, but I do need at least 5 lines of text to be able to display. Thanks for the link to the "calculator-project" that looks almost perfect. Has anyone gone through the Student guide and lab exercises from TI? I'm trying to stumble through it, but I feel that it was designed for someone with way more knowledge then me. Sense I have not ordered a keypad or LCD yet any pointers on what to get, or were to get them would be great. Thanks

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Cool, it proves that if you need something, it was probably already done by someone else, you just have to know how to find it.

As I write this, I am expanding my serial backpack to add the keypad in the same manner, which brings me to the problem with the calculator project. There are no diodes between keypad and the register, meaning that if you press 2 keys from the same column, you are going to short 2 register outputs, messing up your display and possibly damaging you shift register.

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So in an effort to move my little project forward I was looking for an lcd and a keypad to by.

 

Keypad http://www.sparkfun.com/products/8653

LCD http://www.sparkfun.com/products/9568

 

Has anyone used these, or had any experience with either one? I was hoping for a 4x4 keypad but this one will work for now(I can just add user interface buttons right?). The only thing that worries me about the LCD is some of the user reviews, should I just stay away from it? Also has anyone used a commercial LCD like one from an old photo frame?

 

Thanks for your help.

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For an LCD, You could even try the one Mac is selling for $4 shipped:

 

Before you buy, make sure of the interface voltages, is 3.3V ok?, Most of the time it should work fine. You could also request if anyone has a spare keypad in the Buy/Sell forum... maybe you'll find something cheaper.

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For an LCD, You could even try the one Mac is selling for $4 shipped:

 

Please note that I am not selling LCDs. I simply posted a link to the vendors ebay listing........

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Before you buy, make sure of the interface voltages, is 3.3V ok?, Most of the time it should work fine. You could also request if anyone has a spare keypad in the Buy/Sell forum... maybe you'll find something cheaper.

Thanks for the tip. i didn't even think to look at the voltage :shock: . It runs at 5v, so I'll have to find something else. The link to the LCDs you provided is great, but I would rather have 4 lines instead of 2. I will still probably order one to tinker with anyway. Also the link you gave says those LCDs are 5v as well, am I missing something?

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The one you linked to Sparkfun is a serial LCD not a parallel one( the one which I suggested). The Sparkfun one also suggests 5V TTL, whereas the MSP430 you will be running would be at 3.3V TTL. So I'm not sure it will work.

 

Do you want to control your LCD parallel( 4 or 8 lines) or serial(3 lines)?

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I see now, the HD44780 LCD can either be 3.3v or 5v. I would rather use serial (3 lines), but if it comes down to it I can go with parallel. I was just hoping to get more than two display lines on the LCD.

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