TITLE "LM60 based thermometer" List P=PIC16F628A, R=DEC INCLUDE "p16f628a.inc" __CONFIG _CP_OFF & _DATA_CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT #define ENA PORTB,4 #define SDT PORTB,3 #define SCK PORTB,2 #define SCL 2 ; I2C clock line setup #define SDA 1 ; I2C data line setup #define I2C_port PORTA ; I2C port setup #define I2C_conf TRISA ; I2C PIC's direction register CBLOCK 0x20 ; data segment in BANK 0 n:2, dat:2, del cnt, dataIO, ACK ENDC ; code segment ORG 0 ; main code bcf STATUS, RP0 ; activate BANK 0 clrf PORTA ; initialize PORT A clrf PORTB ; initialize PORT B bsf I2C_port, SCL movlw 0x07 movwf CMCON ; comparators OFF bsf STATUS, RP0 ; switch to BANK 1 movlw b'00100010' movwf TRISA ^ 0x80 ; enable input on RA2 clrf TRISB ^ 0x80 ; enable output on PORTB bcf STATUS, RP0 ; back to BANK 0 call init_MAX6950 ; initialize the LED driver loop call requestData ; request data for odd values of mode movlw 250 movwf del call delay ; 0.25 sec delay call getData ; get data for even values of mode call display goto loop ; endless loop ;//////////////// procedures init_MAX6950 movlw 1 movwf dat+1 ; decode register movlw b'00001111' ; enable decoding for all digits movwf dat call write_MAX6950 movlw 2 movwf dat+1 ; intensity register movlw 1 movwf dat ; initial intensity 1/16 call write_MAX6950 movlw 3 movwf dat+1 ; scan limit register movlw 3 movwf dat ; scan 4 digits call write_MAX6950 movlw 4 movwf dat+1 ; config register movlw b'00100001' ; no blinking, normal mode, reset movwf dat call write_MAX6950 return write_MAX6950 ; write a 16-bit word; first byte is reg address movlw 16 ; bits counter bcf SCK ; make sure that SCK=0 bcf ENA ; enable the device write_loop rlf dat, f rlf dat+1, f ; shift out MSB to btfsc STATUS, C bsf SDT btfss STATUS, C bcf SDT ; the data line is set up now bsf SCK ; clock up nop ; short delay bcf SCK ; ... and down addlw -1 btfss STATUS, Z ; all bits sent? goto write_loop ; not yet bsf ENA ; yes - latch in the data and exit return display ; display ADC data in HEX movf n+1, w movwf dat swapf dat, f bcf dat, 7 movlw 0x63 ; digit 3 address movwf dat+1 call write_MAX6950 movf n+1, w movwf dat bcf dat, 7 movlw 0x62 ; digit 2 address movwf dat+1 call write_MAX6950 movf n, w movwf dat swapf dat, f bcf dat, 7 movlw 0x61 ; digit 1 address movwf dat+1 call write_MAX6950 movf n, w movwf dat bcf dat, 7 movlw 0x60 ; digit 0 address movwf dat+1 call write_MAX6950 return requestData bsf PORTA, 0 call start_I2C ; start communication movlw b'11010000' ; MCP3425 address and write movwf dataIO call write_I2C ; write adress byte movlw b'10001000' ; single conversion request movwf dataIO ; 16-bit, PGA=1 call write_I2C ; write configuration byte call stop_I2C ; terminate communication bcf PORTA, 0 return getData call start_I2C ; start communication movlw b'11010001' ; MCP3425 address and read movwf dataIO call write_I2C clrf ACK ; setup the ACK signal call read_I2C ; get MSB movf dataIO, w movwf n+1 ; save it in n+1 incf ACK, f ; setup for NACK signal call read_I2C ; get MSB movf dataIO, w movwf n ; save it in n call stop_I2C ; terminate communication return delay movlw 200 ; this loop takes 1us*5*200 = 1ms addlw -1 ; for PIC @ 4 MHz nop btfss STATUS, Z goto $-3 decfsz del, f goto $-6 return ;;;;;;;;;;;;;;;;;;;;;;;implementation of the I2C interface ; ___ ; DATA: |_______ ; ______ ; SCK : |___ start_I2C ; start setup for I2C interface movlw I2C_conf ; setup FSR to point to TRISC movwf FSR bsf INDF, SDA ; pull high SDA and SCL bsf I2C_port, SCL nop ; delay slot bcf I2C_port, SDA bcf INDF, SDA ; set data low bcf I2C_port, SDA goto $+1 ; wait for slave to detect it bcf I2C_port, SCL ; set clock low return ; ___ ; DATA: ______| ; ______ ; SCK : ___| stop_I2C ; stop setup for I2C interface bcf I2C_port, SCL ; make sure that clock and data bcf I2C_port, SDA bcf INDF, SDA ; lines are low goto $+1 bsf I2C_port, SCL ; release clock line goto $+1 bsf INDF, SDA ; release data line return write_I2C ; write a byte to the I2C bus bcf I2C_port, SCL ; make sure that clock is low bcf I2C_port, SDA movlw 8 movwf cnt ; bits counter w_loop bcf I2C_port, SDA ; preset 0 on data line rlf dataIO, f ; get the rightmost data bit btfsc STATUS, C bsf INDF, SDA ; set data high btfss STATUS, C bcf INDF, SDA ; set data low bsf I2C_port, SCL ; raise clock up nop bcf I2C_port, SCL ; ... and down decfsz cnt, f goto w_loop ; repeat this 8 times bsf INDF, SDA ; get ACK from slave goto $+1 ; let slave respond bsf I2C_port, SCL ; clock up nop ; slave responds OK (hopefully) bcf I2C_port, SCL ; clock down return read_I2C ; read byte from I2C bus bcf I2C_port, SCL ; make sure that clock is low movlw 8 movwf cnt ; bits counter r_loop bsf I2C_port, SCL ; clock up bcf STATUS, C btfsc I2C_port, SDA bsf STATUS, C ; C = data bit bcf I2C_port, SCL ; clock down rlf dataIO, f ; insert it into the data byte decfsz cnt, f goto r_loop ; repeat this 8 times movf ACK, f ; set Z flag bcf I2C_port, SDA btfsc STATUS, Z bcf INDF, SDA ; ACK signal bsf I2C_port, SCL ; clock up goto $+1 goto $+1 nop bcf I2C_port, SCL ; clock down bsf INDF, SDA ; release the data line return END