jakeselectronics
Member
Can someone see what I'm doing wrong here.
It is in relation to checking if the sensor is busy doing a temp conversion...
Resolution is 12 bit so it should take 750mS
How do I properly check the sensors busy status?
I structured it like this so I can put this in the main loop and execute other tasks while the conversion is taking place. Didn't want to use interrupt for this. Open to suggestions on a better way to do this also....
The 1-Wire Subroutines. (Which im confident are fine because they work if I change the main code.
It is in relation to checking if the sensor is busy doing a temp conversion...
Resolution is 12 bit so it should take 750mS
How do I properly check the sensors busy status?
I structured it like this so I can put this in the main loop and execute other tasks while the conversion is taking place. Didn't want to use interrupt for this. Open to suggestions on a better way to do this also....
Code:
MAIN_LOOP
GET_TEMP
; Check FLAG, 4 to determin if temp sensors finished Temperature Conversion and ready for next conversion
BTFSC FLAGS, 4
GOTO CONVERSION_NOT_READY
; Broadcast temperature conversion command to 1-Wire bus
CALL OW_RESET ; Reset
MOVLW H'CC' ; Skiprom (send to all devices)
CALL OW_WRITE_BYTE ;
MOVLW H'44' ; Convert T
CALL OW_WRITE_BYTE ;
BSF FLAGS, 4 ; Set to indicate temp sensors busy
CONVERSION_NOT_READY
TEMPERATURE_CONVERSION_DONE?
CALL OW_READ_BIT ; Initiate Read Time Slots
BTFSS STATUS, C ; DS18B20 transmits a 0 while the temperature conversion is in progress and a 1 when the conversion is done
GOTO CONVERSION_NOT_DONE ; Transmitting 0 therefore NOT done
CALL OW_RESET ; Reset
MOVLW H'CC' ; Skiprom
CALL OW_WRITE_BYTE ;
MOVLW H'BE' ; Read Scratchpad
CALL OW_WRITE_BYTE ;
CALL OW_READ_BYTE ; Move Scrachpad Byte 0 to W
MOVWF TEMP_C_L ; Store in Celsius TEMPLO GPR
CALL OW_READ_BYTE ; Move Scrachpad Byte 1 to W
MOVWF TEMP_C_H ; Store in Celsius TEMPHI GPR
; Clear flag to indicate temp sensors ready for next conversion
BCF FLAGS, 4 ; Temp sensors ready for another Convert T Command
CONVERSION_NOT_DONE
; ... rest of main loop here...The 1-Wire Subroutines. (Which im confident are fine because they work if I change the main code.
Code:
; Dallas 'One Wire' Communication Routines.
; DISABLE INTERRUPTS DURING TIME CRITICAL COMMUNICATION
OW_RESET ; This routine Resets devices on the 1-Wire bus
CALL DQ_LL ; Force the DQ Line to Logic Low
MOVLW (D'500'-5)/5 ; Reset pulse must be held a minimum of 480uS.
CALL DELAY ; For delays from 10uS to 1285uS. Example, MOVLW D'10' for 10uS, MOVLW D'500' for 500uS. (D'n'-5)/5; n must be divisable by 5
CALL DQ_HIZ ; Release DQ Line
MOVLW (D'70'-5)/5 ; Wait for recovery
CALL DELAY ;
BTFSC PORTB, 0 ; Test for 'Presence Pulse'
GOTO OW_RESET ; If not present, Reset
MOVLW (D'430'-5)/5 ; Must wait a minmum of 480uS from when DQ line is released before moving on
CALL DELAY ;
RETURN ;
OW_READ_BYTE ; This routine reads a byte of data from the DS18B20
MOVLW H'08' ; Amount of bits to shift out
MOVWF COUNT ; Store in COUNT GPR
CALL OW_READ_BIT ; Read bit
RRF SHIFT, F ; Rotate bit out of carry into SHIFT GPR
DECFSZ COUNT, F ; Decrement COUNT
GOTO $-D'3' ; If not zero, read next bit
MOVF SHIFT, W ; If zero, move SHIFT GPR to W
RETURN ;
OW_READ_BIT ; This routine reads one bit of data from the DS18B20
BCF INTCON, GIE ; Disable Global Interrupts
CALL DQ_LL ; Force the DQ Line to Logic Low
CALL DQ_HIZ ; Release DQ Line
BSF STATUS, C ; Preset Carry Flag
BTFSS PORTB, 0 ; Test DQ Line
BCF STATUS, C ; If zero, Clear Carry Flag
BSF INTCON, GIE ; Enable Global Interrupts
MOVLW (D'60'-5)/5 ; Wait for Time Slot to end
CALL DELAY ;
RETURN ;
OW_WRITE_BYTE ; This routine writes a byte of data to the DS18B20
MOVWF SHIFT ; Move data to shift into DS18B20 to SHIFT GPR
MOVLW D'08' ; Amount of bits to shift in
MOVWF COUNT ; Store in COUNT GPR
RRF SHIFT, F ; Rotate valid data into Carry Flag
CALL OW_WRITE_BIT ; Write bit
DECFSZ COUNT, F ; Decrement COUNT
GOTO $-D'3' ; If not zero, read next bit
RETURN ; If zero, RETURN
OW_WRITE_BIT ; This routine writes one bit of data to the DS18B20
BCF INTCON, GIE ; Disable Global Interrupts
CALL DQ_LL ; Force the DQ Line to Logic Low
BTFSS STATUS, C ; Test Carry Flag
GOTO $+D'2' ; If zero, leave DQ Line Logic Low
CALL DQ_HIZ ; If not zero, release DQ Line to Logic High
MOVLW (D'60'-5)/5 ; Hold Logic Low, write 0
CALL DELAY ;
CALL DQ_HIZ ; If not zero, release DQ Line to Logic High, write 1
BSF INTCON, GIE ; Enable Global Interrupts
RETURN ;
DQ_HIZ ; This routine forces the DQ Line to an Input / High Impedance state
BSF STATUS, RP0 ; Bank 1
BSF TRISB, 0 ; Make Pin 3 an input, Pullup resistor forces line to logic 1, unless DS18B20 pulls it low
BCF STATUS, RP0 ; Bank 0
RETURN
DQ_LL ; This routine forces the DQ Line to Logic Low
BCF PORTB, 0 ; Clear output latch
BSF STATUS, RP0 ; Bank 1
BCF TRISB, 0 ; Make Pin 3 an output
BCF STATUS, RP0 ; Bank 0
RETURN
DELAY ; This routine can provide delays from 10uS to 1285uS depending on the number moved to the Working register prior to calling the delay
MOVWF DELAYGPR1 ; Move integer to GPR
NOP ; No Operation
NOP ; No Operation
DECFSZ DELAYGPR1, F ; Decrement GPR and place back in itself
GOTO $-D'3' ; Not finished, GOTO here - 3 instructions
RETURN ; Finished, Return