help with PIC 16f877

[naffets_23]

hey

i'm new with the 16f877 and im workin on a project with respect to it and i'm looking for a piece of code where the PIC takes 8 inputs from switches and wen one of these switches are on, it outputs 8 bits to a parallel port on a computer

if any of you can help me, it would be greatly appreciated


also, if it is not too much, can i get an idea of what the schematic would look like

thanks

[SuB-ZeRo]

'for buttons
loop:
if portb.0=0 then goto b1
if portb.1=0 then goto b2
if portb.2=0 then goto b3
if portb.3=0 then goto b4
if portb.4=0 then goto b5
if portb.5=0 then goto b6
if portb.6=0 then goto b7
if portb.7=0 then goto b8
goto loop

'for actions
b1:
high portd.0
gosub bekle
goto loop

b2:
high portd.1
gosub bekle
goto loop

b3:
high portd.2
gosub bekle
goto loop

b4:
high portd.3
gosub bekle
goto loop

b5:
high portd.4
gosub bekle
goto loop

b6:
high portd.5
gosub bekle
goto loop

b7:
high portd.6
gosub bekle
goto loop

b8:
high portd.7
gosub bekle
goto loop

bekle:
pause 1000
RETURN

end

[mister_e]

TRISB=255
TRISD=0
OPTION_REG.7=0 ' enable pull-ups resistor on PORTB
Loop:
    PORTD=~PORTB
    goto Loop

Connect your switchs between PORTB and GND.
All PORTD pins goes to PC thru serie resistor.. let's say 1K

[Dwayne]

Hello Nafetts.

Can't test this code, but it can be used as Psuedo...

TRISB="11111111"
TRISD="00000000"

main:
Portd=0
If Portb.0=1 then Portd=1
if Portb.1=1 then Portd=Portd+2
If Portb.2=1 then Portd=Portd+4
if Portb.3=1 then POrtd=Portd+8
if Portb.4=1 then Portd=Portd+16
if Portb.5=1 then POrtd=Portd+32
if Portb.6=1 then POrtd=Portd+64
if Portb.7=1 then portd=Portd+128

Pause 1000 (pause 1 second)
goto main
end

I believe there is a way to access this through a loop,
but I dont' have my PBP with me to give you proper code.

Dwayne

[naffets_23]

ok thanks alot...i would try these programs out either tomorrow or sometime else this week

[naffets_23]

ok
well our instructor decided to change the school project to using serial instead of parallel communication

i am using pic code for the first time and im not sure how to get the pic to capture the input from the 8 switches and output it.

which ports on the pic do i use?
because when i was checking out the pic schematic, all the ports could be programmed ?!

how do u determine which ports to use and how would u modify the code that SuB-ZeRo gave me for serial?? (thank u very much for ur help SuB-ZeRo)

finally, how do u setup the baud rate??

let me explain
the pic takes the input from the switches and outputs to the serial port on the computer
if i setup the pc's com port to use a baud rate of 9600... how do i setup the pic to output at that baud rate?

please keep in mind, i have never used a pic before but that doesnt mean that u cant throw some moderate code at me... just that ill ask questions later!

thanks for all ur help

[EDWARD]

yo dude are you sure it is to be done in picbasic? just double checking.

get a picbasic manual and read up on the serout and serin commands. itll give you syntax plus an example. it tells baud and other info

also, check out this site that shows how to serially communicate to a visual basic program and a pic. cool stuff.

http://www.rentron.com/VisualBasic.htm

also most of the code ideas above are just ideas dude, not to be copy and pasted into your project.

you use the ports that best suit your application. meaning dont use the anologue ports(if any) when there are free descrete ones. try and use some logic in choosing your ports. like, put all the buttons on one port and other devices on a different one or someting.

also, im not 100% but i think that you going to have to use a MAX232 or similar device to be able to comunicate wit the pc, not sure though. you can still generate serial data without one.

also need to wire your buttons up properly so there is no false triggering.

check out the schematics section of this forum. yo gonna need to take bits of data from different sources and add them together to suite your needs. its not all gonna be laid out in front of you.

[Depot1]

i'm trying to get Qbasic and the 16F876 pic to Talk
VIA RS232 and the Max232 chip
if i start the pic first -nothing happens
if i start QB first then pic i get "Device I/O error" message
.5 sec after pic is started
qbasic may work at 19200 baud which i would like
and i think i would need faster that
4mhz crystal for the pic also

---------------------------------
PBP code here-
---------
DEFINE LOADER_USED 1 'for melabs bootloader
DEFINE OSC 4 'for 20mhz pic
DEFINE HSER_RCSTA 90h 'set port to input
DEFINE HSER_TXSTA 20h 'set port to output
DEFINE HSER_BAUD 9600 'set baud rate
B0 VAR BYTE
B1 VAR BYTE
B1 = 44
B0 = 0
Hseer: HSerout [B1]
HSerin [B0]
IF B0 > 0 Then loop 'go to loop and blink led if value found
GoTo hseer
loop: High 0 'Turn on LED connected to RB0
Pause 50 'Delay for .5 seconds
Low 0 'Turn off LED connected to RB0
Pause 50 'Delay for .5 seconds
GoTo loop 'Go back to loop and blink LED forever
End
-------------------------end PBP code
Qbasic-code below
-----------------
10 CLS
' Open communications (2400 baud, no parity, 8-bit data,
' 1 stop bit,
OPEN "COM1:9600,N,8,1,CD0,CS0,DS0,OP0" FOR RANDOM AS #1
20 INPUT #1, B$
PRINT B$
30 GOTO 20
END

-----------------
Qbasic Loop test works fine
---- looptest.bas
10 CLS
' Open communications (9600 baud, no parity,
' 8-bit data,1 stop bit,
OPEN "COM1:9600,N,8,1,CD0,CS0,DS0,OP0" FOR RANDOM AS #1
20 A$ = "Hello"
Print #1, A$
INPUT #1, B$
PRINT B$
30 GOTO 30 'holds screen
END

[Depot1]

the pic basic list
has been around for long time
they have lots of knowledge
but when send email
Subscribe picbasic-l
i get no responce
please help

[mister_e]

i'm not going trough the Qbasic code since it's really far in my mind but to do a efficient 9600 bauds comm with a 4MHZ crystal you should redefine you USART like...

DEFINE HSER_RCSTA 90h 'set port to input
DEFINE HSER_TXSTA 24h 'set port to output <=== BRGH=1
DEFINE HSER_BAUD 9600 'set baud rate

this will gives you a better error % (0.16% against ~7% with 20h)

Another method to check you serial communication will be to use the serial communication windows of MicroCode Studio. Easy to use, work really good and there's one free version
Download here
Once you're sure that your serial communication work.. do your VB or Qbasic code

[Melanie]

I'd like to add that if your instructor has set you a project, then it's unfair to come on the forum and ask for a solution. Start by reading your PICBasic manual and your QBASIC manual. You'll have learnt nothing if we gave you all the answers. In the case of Depot1 (who's obviously on the same course), take a look at your comments and compare with your code - they don't even match... just a few examples...

DEFINE OSC 4 'for 20mhz pic ... really? So the number 4 means 20MHz?

Pause 50 'Delay for .5 seconds ... close but no cigar!

HSerin [B0] ... and you wonder why your PIC is hanging...

Open communications (2400 baud, no parity, 8-bit data,
' 1 stop bit,
OPEN "COM1:9600,N,8,1,CD0,CS0,DS0,OP0" FOR RANDOM AS #1

Well, is it supposed to be 2400 or 9600 ?

Did you write this or copy it from someone? If we help you graduate, how long would you last when you got a real job.

Read the Manuals... and compare the commands to what you've written (or copied). Please guys, no Private Messages, I'm not going to do your homework or sit your exams for you.

[G8RPI]

I'd just like to add to Melanie's comments,

Instructors have computers and can look at posts on lists too!

Robert G8RPI.

[Depot1]

first off there is no exam and it is not for school
it's my personal work
there is a define for 4 mhz because
i am using a 20 mhz pic,
at 20mhz they do not run stable
do you know what this define is used for ?
the Hserout is before Hserin
i turn on PIC wait to see if something is sent
if it hangs it's afterwards not before
and there is no "pause 50"
unless you see it in some of the comments they do nothing
they are from a program that i started with then rewrote it
perhaps i should have took them out
and i should cleaned up the codes before posting
sorry for the sloppy mess