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Topic: PIC LCD backpack hacking questions (Read 691 times) previous topic - next topic

PIC LCD backpack hacking questions

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I found your LCD BACKPACK data and made PCB and assembled that. Your test programm start and i have fail only LCD backligh, and i cannot found yet why. But my main idea was to use you BACKPACK to connect LCD to PC and modify your PCB desighn to connect yet small (3*4) keyboard, to build interface to enter data to PC. I trying that but with total lack of expiriance and with that Microchip usb stack, i have stuck. So if you have some time, can you give me some advices and ansvers on my questions?

1. To connect (3*4) keyboard to PIC i need yet 7 IO pins, but cose we limited with that on current PCB, i want use PIC18F4455 and change a little your PCB. That is correct idea? I did that keyboard running code on PIC16F84 - my old friend, but that was too long time ago when USB was not used in PICs yet.

2. That is possible to use Microchip USB stack to make bidirectional data transfer like keyboard must done?

3. Do you have any idea - can found some guy who can change your code to run LCD on PIC18F4455 and add here keyboard, for money? I think that will be faster for me to education work with working code, that USB stack is hard to understand for me. My development language was Assembler and your code inside MPLAB looks yet wierd.

4. Maybe you can give any advice in that keyboard adding task?

Best wishes,
archer.

1. yes, that sounds good. You just need a few more pins.

2. I'm not sure what you meat. The USB is a virtual COM/serial port, it is bidirectional. I'd guess your keyscans would happen on chip and the PIC would send the keys back to the PC.

3. I'm sorry, I don;t know any coders that work for pay. About everyone here is a hobbyists, some with day jobs in electronics too, not many people take small projects. I'll post this in the public forum in case it sparks a passion in anyone.

4.I'd need to see the keypad datasheet and know how it works, I have not used one before. I'd guess you could set up an interrupt and read the key on any interrupt with some denouncing logic to prevent false key-presses.
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Re: PIC LCD backpack hacking questions

Reply #1
For keyboard interfacing, check here. It talks about the keypad library for Arduino. You can later check the actual library for how they do it. Basically they scan they keyboard each time you use getKey() function and do software debouncing.

I used a keypad with PIC24F series in assembly and C. Interrupt is the best way, you don't have to check for key presses in a loop and you can do other tasks. I can easily write a C code that does a scan if you want. The interrupt method is hardware specific, so that can take some time.