Peek Poke pic16f870

[Eric123]

I have made some changes to my code and am understanding why it was doing what it was doing. I am trying to use the examples from the PICBASIC compiler hand book page 47 to write my code. I am trying to use the first four pins on PortA and PortC to control two motors through an H bridge using port B pins 4,5 for motor 1 and 6,7 for motor 2. The example code says:

Loop: Peek PortA,B0 'get current portA pin states to variable B0
If bit0=1 then zerohigh
If bit1=0 then onelow
goto loop

zerohigh: high 0
gotoloop
onelow: low 1
goto loop
end


So this is why in my code I was using bits. According to the Pg 20 of this manual that came with my basic compilier it says that the first tow bytes , B0 and B1 may also be used as bit variables. Bit0...Bit7 for B0 and bit8...bit15 for B1. So this is why I had the use of bit8 in my orginal code. But may be there is a better way to do this and if so I would like to know. Here is my revised code.

symbol cmcon=$1f
poke cmcon,7
symbol adcon0=$9f
poke adcon0,7
symbol adcon1=$9f
poke adcon1,7

start:
peek 5, B0
if bit0=0 then A
if bit0=1 then D

peek 7, B1
if bit8=0 then B
if bit8=1 then C
goto start


A: low 6: high 7: Return
B: low 4: high 5: Return
C: low 7: Return
D: low 5 Return

Please tell me how I can fix my code It still seems like peek and poke arent working right for me.

Thanks for you Help.

[paul borgmeier]

Eric,

This will get you closer - I maintained your logic exactly, which, looks to me, to be a bit troubling as SKIMASK noted. You also will want to get a copy of the 16F870 datasheet to go with the manual. Email back if you want more.

;symbol cmcon=$1f	; 16F870 has no comparators and $1f is ADCON0 not CMCON
;poke cmcon,7	; this line and above not needed for the 18F870
;symbol adcon0=$9f  ; $9F is ADCON1 not ADCON0 – these two lines repeat the next two
;poke adcon0,7
symbol adcon1=$9f
poke adcon1,7	; Make all of PORTA Digital rather than analog

Poke, $85, %00000011	; make pins 0 and 1 on PORTA inputs, the rest outputs
Poke, $87, %00000011	; make pins 0 and 1 on PORTC inputs, the rest outputs
Poke $86, %00000000    	  ; make all of PORTB outputs
Poke $05, 0			; make all outputs of PORTA low
Poke $06, 0			; make all outputs of PORTB low
Poke $07, 0			; make all outputs of PORTC low

start:
peek 5, B0			; read PORTA into predefined variable B0
if bit0=0 then A		; if B0.0 = 0 then GOTO A (no gosub in if statement)
ReturnFromA:
if bit0=1 then D		; if B0.1 = 1 then GOTO D (no gosub in if statement)
ReturnFromD:
peek 7, B1			;  Read PORTC into B1
if bit8=0 then B		; if B1.0 = 0 then GOTO B
ReturnFromB:
if bit8=1 then C		; if B1.0 = 1 then GOTO C
goto start

A: low 6: high 7	; make PORTB pin 6 low and pin 7 high
Goto ReturnFromA

B: low 4: high 5	; make PORTB pin 4 low and pin 5 high
ReturnFromB
C: low 7		; make PORTB pin 7 low
Goto Start
D: low 5  		; make PORTB pin 5 high
Goto ReturnFromD
END

oh, I have not tried this - I do not use PBC anymore ... and you might want to start your project by trying to blink and LED or two rather than trying to code a complete program.

[skimask]

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