serial out 9 bits?

Archiver

Hi all,
I am trying to set up some serial communication between a BSII and an PIC16F84
for my current project.

I have found some code to do serial coms in software on the PIC (it has no
hardware UART) but from reading the code it appears it is expecting 1 start
bit, 8 data bits, no stop bit. I have written some test code for my BSII using
the serin and serout commands.

My question is how do I serout 9 bits, and is serout the most appropriate stamp
command to be using for this?

Thanks for any help,
James Fitzsimons

Archiver

the start bit is not actually a bit it is the first transition from high
to low and is called a mark. I had a project that used the exact same
chip. I have exactly what your looking for, if you have a fax number i
could fax it to you . Do you have a pic programer?


On Fri, 02 Nov 2001 16:25:09 +1300 (NZDT) jamesfit@p...
writes:
> Hi all,
> I am trying to set up some serial communication between a BSII and
> an PIC16F84
> for my current project.
>
> I have found some code to do serial coms in software on the PIC (it
> has no
> hardware UART) but from reading the code it appears it is expecting
> 1 start
> bit, 8 data bits, no stop bit. I have written some test code for my
> BSII using
> the serin and serout commands.
>
> My question is how do I serout 9 bits, and is serout the most
> appropriate stamp
> command to be using for this?
>
> Thanks for any help,
> James Fitzsimons
>
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Archiver

Hi Kelvin,
thanks for you response! I guess I have mis-understood the meaning of start
bit.... I am a bit confused now. How do you get that transition if you don't
send a high bit to start with?

I don't have a fax number at home, only email. You could fax it to me at
work on +64 4 4957308 but I do live in New Zealand!

I am using a PIC programmer I built from a kit I brought from
www.phanderson.com It is called the morgan PIC programmer.

Thanks again for you help,
regards
James Fitzsimons


> the start bit is not actually a bit it is the first transition from high
> to low and is called a mark. I had a project that used the exact same
> chip. I have exactly what your looking for, if you have a fax number i
> could fax it to you . Do you have a pic programer?
>
> >
> > My question is how do I serout 9 bits, and is serout the most
> > appropriate stamp
> > command to be using for this?

Archiver

Hi James

Sorry your confused . I guess I should have been more clear.
After the first high to low transition the program waits 1 bit time (the
start bit) after which
it checks the serial pins state , this next bit is the first data bit.
There is also a stop bit, the same as the start bit ,but thats not
mentioned aymore.

If your ready heres the serial program.
I used the 84 chip as a mirror for the bs2,I set up a counter and sent
the number to the 84 which sent it back to the bs2 so I could read it .
This program is at the end.
I dont thin I have any typeOs
Let me know how it goes.

The baud rate is tested at 2400 max (the program is set to 2400)
The recieve and transmit pin is portA pin2
If you want to make the baud rate 1200, double the bit_k value.
4mhz xtal , use square metal can type
watchdog timer off


list p=16c84
radix hex
w equ 0
f equ 1
status equ 0x03
carry equ 0x00
bit_k equ d'103' ;bit delay value, use to change baud rate
del_cnt eqy 0x0c
bit_cnt equ 0x0d
dx equ 0x02
count1 equ 0x0f
count2 equ 0x10
rec_reg equ 0x11
port_a equ 0x05

org 0x00
recv movlw 0x02
tris port_a ;make porta input
start nop
nop
btfsc port_a,dx ;check for start bit
goto start
movlw 0x08 ;set for 8 bits
movwf bit_cnt
clrf rec_reg
r_next
call bit_del ;delay 1 bit time
btfss port_a,dx ;check pin for high
bcf status,carry
btfsc port_a,dx ;check pin for low
bsf status,carry
rrf rec_reg,f ;shift bit in register
decfsz bit_cnt,f ;decrement 8 bit counter
goto r_next
call bit_del ; stop bit
movf rec_reg,w
call pause ;slow things down a little
;************************************************
;this is almost the same as above except bits are shifted out instead of
in

; transmit

trans
movlw 0x00
tris port_a ;make porta output
clrf port_a
clrf count1
clrf count2
clrf del_cnt
bcf status,carry
xmtr movlw 0x08
movlw bit_cnt
bcf port_a.dx
call bit_del
x_next
bcf status,carry
rrf rec_reg,f
btfsc status.carry
bsf port_a,dx
btfss status,carry
bcf port_a,dx
call bit_del
decfsz bit_cnt,f
goto x_next
x_stop bsf port_a,dx
call bit_del
goto recv

;*********bit delay********************************

bit_del
movlw bit_k
movwf del_cnt
dec_cnt
nop
decfsz del_cnt,f
goto dec_cnt
return


;***************************************
Bs2 comm84

x var byte
dat var byte

loop:
x = x + 1
serout 7,396,[noparse][[/noparse]x]
serin 2,396,300,skip,[noparse][[/noparse]dat]
skip:
debug ? x ,cr
debug ? dat,cr
goto loop

Archiver

HI James

I need to make a correction, I left out a routine. Its late after
midnight here,sorry

I need you to add this to the end of the program.
What this if for is to give the stamp time to get ready to receive the
transmition
form the 84 chip
; pause between transmitions

pause
movlw 0xfb
movwf count1
loadn
movlw 0xfb
movwf count2
deccn
decfsz count2,f
goto deccn
decfsz count1.f
goto loadn
return
end

This is just a time delay loop within a time delay loop.
Its done to make longer time delays. Calling this time delay 3 times will
give about
a half second delay. It may be useful to you with other programs.

good luck
Kelvin

Archiver

Hi Kelvin,
just wanted to say a big thank you for the code you sent through. I really
appreciate your taking the time.

kind regards,
James Fitzsimons