On 05-Jan-12 21:00, Adam Walley wrote:
> Here is the code I am using with the MPLAB IDE v8.33
> Sorry for any bad formatting. The code is very crude because I am still
> testing and debugging (that is also why there is an eeprom write and the
> flashing LEDs - these confirm that my code has run).
>
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ASM =3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
> ;12F675 send 'K' byte to PC via RS232 (GPIO1)
> ; as basic as possible to test correct code format
> ;
>
>
> #include<p12f675.inc>
> errorlevel  -302               ; suppress message 302 from list file
>
> __CONFIG  _CP_OFF&  _WDT_OFF&  _BODEN_OFF&  _PWRTE_OFF&
> _INTRC_OSC_NOCLKOUT&  _MCLRE_ON&  _CPD_OFF

Your problem is _MCLRE_ON. This connects the internal reset circuitry to=20
external pin #4 which is floating.

When you use battery power, your power supply is noise free and this=20
floating input stays at logic level 1 (which is pure luck).

As soon as you connect the ground wire, your device starts to receive=20
more RF noise and this changes the MCLR logic level randomly and resets=20
the chip repeatedly.

Use _MCLRE_OFF or connect your reset pin #4 to Vcc through a resistor.

Djula



>
> ;***** Reset vector *************************************************
> org 0x00
> nop
> goto init
>
> ;***** Assign Constants Value ***************************************
> #define BANK1 banksel 0x80 ;Select Bank1
> #define BANK0 banksel 0x00 ;Select Bank0
>
> CLOCK   EQU     4000000 ; Set the clock as 4 MHz
>
> ;***** Assign variables *********************************
>
> addr EQU 0x20 ; address for EEPROM access
> dat EQU 0x21 ; value for EEPROM I/O
> cnt EQU 0x22 ; counter
> pins EQU 0x23 ; TRISIO pin status buffer
> io_tmp EQU 0x24 ; GPIO status buffer
> delay_temp EQU 0x25 ; Required for "delay.inc"
> byte EQU 0x28 ; temporary byte buffer
>
> ;***** MAIN *********************************************
> init
> clrf cnt
> clrf dat
> clrf addr
> movlw b'00111001' ; GPIO 1,2 outputs
> movwf pins ; store in pin buffer
> BANK1
> movwf TRISIO ; set I/O pins
> clrf ANSEL ; make all I/O ports digital
> BANK0
> movlw 0x07 ; comparator OFF bits
> movwf CMCON ; switch it off
> bcf ADCON0,ADON ; switch off A/D converter
> clrf io_tmp ; turn off i/o pins in buffer
> clrf GPIO ; turn off i/o pins
> movlw 0x05 ; LOOPS
> movwf cnt ; init counter
> movlw 0x50 ; initial address value
> movwf addr ; set address
> call ewrite ; write '00' to EEPROM for start
> BANK0
> incf addr,1 ; add 1 to address
>
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> call tx_hi ; set TX pin high to begin
>
> loop
> call flash ; FLASH LED
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
>
> ; ------------------------------------------------<K>
> ; send 'T' at 9600 baud
> ; binary: 00101010 LSB->MSB
> ; using a 4 MHz chip
> ; 1 / 2400 baud =3D 416.6667 cycles per bit
> ; 1 / 4800 baud =3D 208.3333 cycles per bit
> ; 1 / 9600 baud =3D 104.1667 cycles per bit
>
> call tx_lo ; START bit [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_lo ; (0)0101010 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_lo ; 0(0)101010 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_hi ; 00(1)01010 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_lo ; 001(0)1010 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_hi ; 0010(1)010 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_lo ; 00101(0)10 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_hi ; 001010(1)0 [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_lo ; 0010101(0) [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> call tx_hi ; STOP bit [   8]
> call delay50 ; [  58]
> call delay20 ; [  78]
> call delay20 ; [  98]
> call delay6 ; [ 104]
>
> BANK0 ; switch back to Bank0
> decfsz cnt,1 ; dec cnt by 1
> goto loop ; cnt>0, keep looping
> goto finish ;
>
>
> ;***** TX on GPIO1 **************************
> tx_hi ; 8 cycles
> BANK0 ; for GPIO
> bsf io_tmp,1 ; GPIO1 pin ON
> movfw io_tmp ; move io_tmp to W
> movwf GPIO ; copy new state to GPIO port
> return
>
> tx_lo ; 8 cycles
> BANK0 ; for GPIO
> bcf io_tmp,1 ; GPIO1 pin OFF
> movfw io_tmp ; move io_tmp to W
> movwf GPIO ; copy new state to GPIO port
> return
>
> ;***** FLASH LED **************************
> flash
> BANK0 ; for GPIO
> bsf io_tmp,2 ; GPIO2 pin ON
> movfw io_tmp ; move io_tmp to W
> movwf GPIO ; copy new state to GPIO port
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> bcf io_tmp,2 ; GPIO2 pin OFF
> movfw io_tmp ; update io_tmp
> movwf GPIO ; copy new state to GPIO port
> movlw 0xc8 ; 200 milliseconds
> call delay_ms ; wait
> return
>
> led_on
> BANK0 ; for GPIO
> bsf io_tmp,2 ; GPIO2 pin ON
> movfw io_tmp ; move io_tmp to W
> movwf GPIO ; copy new state to GPIO port
> return
>
> led_off
> BANK0 ; for GPIO
> bcf io_tmp,2 ; GPIO2 pin OFF
> movfw io_tmp ; move io_tmp to W
> movwf GPIO ; copy new state to GPIO port
> return
>
> ;***** FINISH *****************************
> finish
> call tx_lo ; switch off TX pin
> movlw 0x64 ; 100 milliseconds
> call delay_ms ; wait
> call led_on
> movlw 0x32 ; 50 milliseconds
> call delay_ms ; wait
> call led_off
> movlw 0x32 ; 50 milliseconds
> call delay_ms ; wait
> call led_on
> movlw 0x32 ; 50 milliseconds
> call delay_ms ; wait
> call led_off
> movlw 0x32 ; 50 milliseconds
> call delay_ms ; wait
> call flash
> ; mark end in EEPROM with 'BB'
> movlw 0xBB ; end marker
> movwf dat ; prepare for EEPROM
> call ewrite ; write to EEPROM
> BANK0
> incf addr,1 ; add 1 to address
> sleep
>
> ;***** Include routines *****************************
> include "delays.inc"
> include "eeprom_write.inc"
>
> end
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ASM =3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--=20
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