So I had one of those cheap calculators from walmart and it cracked in my bag for school. The display is still fine and I was wondering if it would be possible and what it would take to turn it into a USB powered LCD Display. I of course would tell it how to display the letters and stuff. My first feat is to figure out how to communicate with the display through USB and I just can't seem to find any information on it. Anybody with some insite would be great. and before you start saying to buy this and that, I'm trying to do this simply with hard coding and some wiring. If that's completely impossible I'll consider buying something but I'd like to exhaust all other possibilities before I do that. Any advice??
calculators crystal displays are divided into segments that you can switch on an off. some even are just divided like the common LED 7-segment but alot of them under that glass. i dont know of anyweb site that shows you how interface them, but there is an article on circuitcellar magazine that details the procedure cant remember which issue though.
i cant find that article but here is some similar : http://www.circuitcellar.com/library/print/0798/May96/May96.pdf also try this- From the Bench: Demystifying LCD Muxing from 1999 july's issue. (no link got to get paper) you might find this usefull: http://www.futurlec.com/LED/40LCD.shtml
Awesome these articles look great. You also seem like the right person to ask. Do you know of any articles explaining in depth the protocol and how exactly USB works? Because my problem now is can I just hook them up and turn them on/off with software on here or do I need to build a controller too and how exactly that data will be sent to the controller and stuff. I looked on how stuff works .com but it's mostly less tech stuff like that there's 4 wires in it and what they're for and stuff... I was looking for more like how it sent the data it sends and exactly how it's read and used. Thanks for everything so far, Alex
hey alex i am searching for the rgiht article also to learn about USB,but this one is good: http://www.semifluid.com/?p=23 but regarding interfacing the whole thing to a computer i would go with the serial port because its the simplest and you dont need the speed of USB. and yeah you just hook up the lcd to your microcontroller of choice and start tuning segment on/off. you could also make it accept input(digits) from a computer through serial port and display it.
Is it possible to do it without the microcontroller? What part exactly does the microcontroller do? Because my hope was to not have to add anything I was trying to do this as from scratch as possible. I mean obviously if it must be done it must be but I was hoping to just be able to write the code to send the power to the right segments. Or is the controller the part that tells it which connectors to send power to by the segments I tell it?? Also, is there any way I can use the controller from the calculator itself and just mod it to my liking?
Hi alex, you will need a microcontroller of some description, most likely a PIC. The microcontroller is the part of your system that takes data from the USB port, interprets it, and actions it with relation to your LCD. Theres no way of getting round that. Look at it this way, theres only 2 data pins on a USB port, without a microcontroller, how are you ever going to control ALL of those parts of the screen? dragon2309
Ya, I figured, but do you think I could use the controller for the calculator or is it too different?
I also have an alarm clock that I can tear apart for the controller and lcd if that would make this more practical... lol
as dragon2309 pointed out you need a microcontroller to interpret the signal coming from the computer and act upon it. and no i dont think you can use the alarm clock's board. your better off doing it from scratch. you seem to be confused about the word controller. here is what you suppose to do Code: ---------------------> +-------+ serial link <--------------------- | | ---------------------> LCD Glass | uC | (tons of wires) +-------+ your serial link is what ever you decide to use to send data to the microcontroller (USB/RS232/I2C...). the controller then interpret the data (which you will program it to tell it how it can do that), and switch on/off segments on the LCD by sending HI/LOW signals to certain pins on the LCD. ***fixed
you program the microcontroller to do what you want. www.microchip.com unless you have experience in programming, this may be above your head (no offense)
No offense taken. And actually, it's the hardware part that's above my head seeing as microcontrollers I've seen range from $80+ I was hoping to build my own. I'm a very confident programmer and catch on quickly to different languages so my problem is figuring out the wiring and stuff. BTW everyone I found an awesome site: http://www.societyofrobots.com I don't know if you all know about it or not but it's very in depth and explains a LOT!
ok, the microcontroller itself is just a single chip (possibly two) the entire board that these reside in is the interface board. So I'm REALLY hoping you meant interface board and not microcontroller (seeing as you can get the microcontroller chips for free..) In answer to your earlier wuaestion "how will the microcontroller know what pin to send data to" well, thats a two part question really. First you start with your software on your PC, depending on how you go about this, you could use something like LCDSmartie, but i doubt your LCD is compatible with it... eaither way, the software on your PC will send out a data signal to the MCU (microcontroller unit) by default there is no code on the MCU, its empty, like a blank disk if you will, its up to you to program it first so it knows how to handle the data that you send to it. Now im not a programmer, I get lost in the technical bits, i just know how they work and fiddle about with them. Basically, you program into the MCU how to handle events and the data being sent to it. You also program into it what it should do when it gets this data, what pin tp set HI what to set LO and what (if any) data stream it needs to pass on. Once you got all that worked out, its all nice and simple, you tell the software on your PC to send a signal to your MCU that in turn sends the correct signal to your LCD... I've still got to wonder though, why are you using an old calc lcd, a properly supported (and much more versatile) lcd will set you back a max of £5-10 GBP ($10-15 USD)... If you went that route, you have hundreds of thousands of people on forums ready to help, because they are used EVERYWHERE, even I've rigged one of those up. dragon2309
1. Thank you, actually I was under the impression the board itself was the micro controller not the chip. Sorry, n00b mistake lol but thanks for correcting me there Also, thanks for explaining exactly how the microcontroller would control the LCD I get it now basically the MC has code on it and when it gets a signal it looks at what the signal says and by what it says decides which pins to send high and low signals too. 2. I've thought of just buying one but this is also a principal thing. I want to learn from testing it and experimenting rather than just buying the kit and everything for it. I was just hoping to do it more from junk around the house. Another question, when people talk about the different types of codes like (Arudino or whatever) is that something you load on after you have the MC? Since you said it came empty? Is that what the boot loader is for? Thanks, Alex
