Quick 4x4 keypad matrix question

[triton99]

Thanks for the reply Archangel. In response to your questions...

1. Why are you putting in LCD defines if you are using the USART, Do you want dual display?
The LCD is used just for quick on-the-spot feedback. It was part of another program, so I usually just cut-and-paste it into other programs. The USART is just for debugging purposes. Plus it remindes me of the old BBS days .

2. Since you did not specify which PIC you are using, which port is your PIC equipped to use the USART ? Is it the same as the keypad uses?
At the beggining I stated I was using an PIC 16F877 @ 20 mhz. The hardware USART TX/RX are ports C6/C7 on the 16F877 which are only being used for serial communication. The keypad is is connected to PORTB.0 to PORTB.7.

3. Why did you change the value of the resistors ? I suspect Bruce proved out his design before posting it on his website.
I was under the impression that the value of the resistors were not that important to a certain extent. While researching keypad matrices, a few people stated that any value <= 10k would be sufficient. I had 1k resistors with me at the time so i gave it a shot. I just replaced the 1k resistors with 270-ohm. It seemed to make the problem occur only on one button (row3-col1). While pressing the button repeatedly, the value displayed will sometimes be the value of the button directly below it, but only intermittently.

By changing the 1k resistors for 270 helped eliminate the problem on all the buttons except the one (row3-col1). I still cant figure what is causing this.

thanks again for the help.

Sean

[Archangel]

Thanks for the reply Archangel. In response to your questions...

1. Why are you putting in LCD defines if you are using the USART, Do you want dual display?
The LCD is used just for quick on-the-spot feedback. It was part of another program, so I usually just cut-and-paste it into other programs. The USART is just for debugging purposes. Plus it remindes me of the old BBS days .

2. Since you did not specify which PIC you are using, which port is your PIC equipped to use the USART ? Is it the same as the keypad uses?
At the beggining I stated I was using an PIC 16F877 @ 20 mhz. The hardware USART TX/RX are ports C6/C7 on the 16F877 which are only being used for serial communication. The keypad is is connected to PORTB.0 to PORTB.7.

3. Why did you change the value of the resistors ? I suspect Bruce proved out his design before posting it on his website.
I was under the impression that the value of the resistors were not that important to a certain extent. While researching keypad matrices, a few people stated that any value <= 10k would be sufficient. I had 1k resistors with me at the time so i gave it a shot. I just replaced the 1k resistors with 270-ohm. It seemed to make the problem occur only on one button (row3-col1). While pressing the button repeatedly, the value displayed will sometimes be the value of the button directly below it, but only intermittently.

By changing the 1k resistors for 270 helped eliminate the problem on all the buttons except the one (row3-col1). I still cant figure what is causing this.

thanks again for the help.

Sean

Hi Sean, Ok . . .
1.OK . . . had to ask . .
2. Sorry old eyes, I missed that. Ok that's good.
3. Looked at Bruce's page again, his statement proves you right . . . non critical.
This code is floating around the forum in many threads, with many variations, and the only thing I see is no TRIS settings for your ports B,C, & D. In the 1 Mr._E did he set the portb Tris as follows: TRISB = %11110000 , he also used an interrupt to detect the keypress, it maybe your finger is faster than your loop, especially given you are using 3 different display protocols. I would comment out any code you are not pressed to use and see if it improves, also you might consider debug over serout as it executes faster using less code space ( or so they tell me) I have not yet proven that last statement to myself, but it is a bit faster, in terms of how long a loop takes to execute,
oh and try these defines (from mister E's famous picmulti calc)

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 129 ' 9600 Baud @ 20MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

[mackrackit]

The program kinda of works....sometimes when a button is pressed, the number sent via HSEROUT is actually the number below it.

i.e. Say the number "3" is pressed...most of the time the number "3" is displayed...but sometimes the number displayed will be "6", which is the button just below the "3" on the keypad.

Double check your hardware.

[Archangel]

What's in the INCLUDE "ansi.inc" file ?

[triton99]

I just assembled the same circuit using an 16f88 instead of the 16F877. Using the same circuit and code[plus changes for the 16F88], the program works perfect.

These are the register setting I use on the 16F88.

CMCON =     7                   '// PortA = digital I/O
OPTION_REG.7  =  0              '// Enable PORTB pull-ups
ADCON1  =  7 
ANSEL=%00000000                 '// set all analog pins to digital
ANSEL = 0                       '// disable ADC

With the circuit working on the 16F88, I resumed working on the 16F877.

I rebuilt and re-checked the wiring on the 16F877. I also got rid of all the extra LCDOUT and HSEROUT commands, while using only the SEROUT command, just like the Bruce's original example. It still has the weird problem. I just cant seem to pinpoint what is causing the error. Its weird too, because I dont have to be pressing the button fast....it does it even if when I press the button slowly. Every once in a while it will display the number below instead of the actual number. Arghhhhhh!!!! I love this stuff .

*Archangel, the "ANSI.INC" was from Darrel Taylors easy ANSI module for PBP.

http://www.pbpgroup.com/modules/wfse...hp?articleid=9

It is the main reason I wanted to use HSEROUT. The ansi.inc only works with the hardware USART, and not with SEROUT(2).

Thanks for the help, Im not giving up on this.

Sean

[Archangel]

Ok, just wanted to know, oh and I do see where you set TrisB in your orig modified code. Maybe as Dave mentioned there is a hardware problem, bad breadboard or the pic it'self. Those breadboards get corrosion inside them and then the fun begins.

[mister_e]

Internal pull-up may sucks, check OPTION reg in the datasheet and see what happen when you set a pin to output... probably the internal pull-up get disabled 'till you set them again... use external one and post your results.