; SDI-12 transmitter - accepts commands from the PC, buffers them, then sends them out via SDI-12 ; Received data is passed back directly to PC, bypassing this code/hardware entirely. ; Version 1, sjm, 31 May 2010 list p=16f688 #include errorlevel -302 radix decimal __CONFIG _CP_OFF & _CPD_OFF & _BOD_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT & _FCMEN_OFF & _IESO_OFF & _MCLRE_OFF cblock 0x20 ; (Maxmium of 5Fh or 95d bytes available) temp1: 1 temp2: 1 data_buff: 16 ; data buffer endc ; IO pin definitions #define DIR_SW PORTC,3 ; Direction switch #define SPARE1_LED PORTC,2 ; #define WAIT_LED PORTC,1 ; #define BREAK_LED PORTC,0 #define SPARE2_LED PORTA,2 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ORG 0x0 ; setup IO pins bsf STATUS,RP0 ; bank 1 clrf ANSEL ; digital IO movlw b'00111011' ; port A pins = inputs, except 2 = output movwf TRISA movlw b'00010000' ; all port C pins = outputs except 5, = uart rx movwf TRISC bcf STATUS,RP0 ; bank 0 movlw 0x07 movwf CMCON0 ; setup serial port bsf BAUDCTL,BRG16 ; use 16 bit baud rate generator bcf TXSTA,BRGH ; use low speed baud rate movlw d'207' ; 207=1200 baud movwf SPBRG ; transmitter bcf TXSTA,SYNC ; setup async operation bsf TXSTA,SPEN ; configure pin as uart tx bsf TXSTA,TXEN ; enable transmitter ; receiver bsf RCSTA,SPEN ; configure pins as uart rx/tx bcf RCSTA,SYNC ; setup async operation bsf RCSTA,CREN ; enable receiver ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; start: bsf SPARE1_LED ; Turn off ? LED bsf WAIT_LED ; Turn off wait_time LED bsf BREAK_LED ; Turn off BREAK LED bsf SPARE2_LED ; Turn off ? LED ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; read_cmd_from_logger: bsf DIR_SW ; change switch direction to receive (HI-Z SDI-12 bus) movlw data_buff movwf FSR get_cmd_byte: call receive_byte movwf INDF ; save into data buffer incf FSR,f sublw '!' ; is it end of command? btfss STATUS,Z ; Yes, skip goto get_cmd_byte ; No send_cmd_to_sensor: bcf DIR_SW ; change switch dir to transmit (micro drives SDI-12 bus) SC_top: call send_break ; This will take 12 ms call wait_10ms ; Mark after sending break movlw data_buff ; load pointer movwf FSR SC1: movf INDF,w call send_byte movf INDF,w ; get same char again incf FSR,f sublw '!' ; End of command? btfss STATUS,Z ; Yes, skip goto SC1 ; No, get next char goto read_cmd_from_logger ; back to top of main loop ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Subroutines follow - functions that are called, and return, ; as opposed to code that jumps or branches. These functions all ; alter the stack. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Send a byte via the UART ; Data to be sent must be in W as an 8 bit character ; Parity is calculated manually, resulting in 7E1 send_byte: btfss TXSTA,TRMT ; PIR1,TXIF goto send_byte call calc_parity ; since PIC doesn't support 7E1 movwf TXREG wait_for_sent: btfss TXSTA,TRMT goto wait_for_sent return ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Receive an 8 bit character from the UART, encoded as 7E1 ; Partity bit is ignored, leaving a 7 bit character ; Data received is returned in W receive_byte: btfss PIR1,RCIF ; received a char yet? goto receive_byte ; No, keep looking btfss RCSTA,FERR ; Was there a framing error? (ie, Break) goto bypass_break ; No, treat it as a normal char bcf BREAK_LED ; Turn on LED to indicate Break movf RCREG,W ; flush RX FIFO, and ... goto receive_byte ; ... look for next char bypass_break: bsf BREAK_LED ; Turn off LED movf RCREG,W andlw 0x7F ; mask out parity bit return ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Calculates parity of a 7 bit value and puts parity bit in 8th position ; Byte to process should be passed in W, result is returned in W ; Must clear carry bit before rotating calc_parity: movwf temp1 bcf temp1,7 ; start with even parity, set this bit for odd swapf temp1,w xorwf temp1,w movwf temp2 bcf STATUS,C rlf temp2,f bcf STATUS,C rlf temp2,f xorwf temp2,f bcf STATUS,C rlf temp2,w xorwf temp2,w andlw 0x80 iorwf temp1,w return ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Send a break sequence on the serial line. ; This is required by the SDI-12 standard to wake up the sensor. ; Assuming TXEN is already enabled - saves an instruction ; BREAK confuses the PC UART, don't send when testing with PC send_break: ; return ; TEMPORARY - only for PC UART testing - REMOVE for production! ; change the baud rate to a non-standard value, in order to get ; a 12ms break period movlw d'230' ; 230 gives exactly 12.0ms break movwf SPBRG bsf TXSTA,SENDB ; enable break mode movwf TXREG ; write anything to start transmission wait_break: ; wait for break to finish btfss TXSTA,TRMT goto wait_break movlw d'207' ; reset baud rate 207=1200 baud movwf SPBRG return ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; SDI-12 standard requires marking periods of at least 8.33ms after ; sending a break, and before issuing a response. This loop takes Xms. wait_10ms: movlw 11 movwf temp2 w1: movlw 250 movwf temp1 w2: decfsz temp1,f goto w2 decfsz temp2,f goto w1 return end