Added module for SI7021 temp/humidity sensor.
This commit is contained in:
Martin Preuss
438
avr/si7021.asm
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438
avr/si7021.asm
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; ***************************************************************************
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; SI7021 module
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; (c) 2023 Martin Preuss
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;
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; ***************************************************************************
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; defines
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.equ SI7021_FLAGS_PRESENT = 0x80
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.equ SI7021_FLAGS_TEMP_VALID = 0x40
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.equ SI7021_FLAGS_HUM_VALID = 0x20
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.equ SI7021_FLAGS_LASTWASTEMP = 0x10
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.equ SI7021_FLAGS_ERROR_MASK = 0x07
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; ***************************************************************************
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; data
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.dseg
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si7021DataBegin:
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si7021Flags: .byte 1
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si7021FirmwareRevision: .byte 1
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si7021LastTemp: .byte 2
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si7021LastHumidity: .byte 2
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si7021DataEnd:
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; ***************************************************************************
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; code
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.cseg
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; ---------------------------------------------------------------------------
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; SI7021_Init
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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SI7021_Init:
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ldi xh, HIGH(si7021DataBegin)
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ldi xl, LOW(si7021DataBegin)
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clr r16
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ldi r17, (si7021DataEnd-si7021DataBegin)
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rcall Utils_FillSram
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; check presence
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rcall si7021CheckPresence
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brcc SI7021_Init_error
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lds r16, si7021Flags
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ori r16, SI7021_FLAGS_PRESENT
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sts si7021Flags, r16
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; get firmware revision
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; rcall si7021ReadFirmwareRevision
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; brcc SI7021_Init_error
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; sts si7021FirmwareRevision, r16
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sec
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ret
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SI7021_Init_error:
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clc
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ret
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; ---------------------------------------------------------------------------
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; SI7021_Fini
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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SI7021_Fini:
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sec
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ret
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; ---------------------------------------------------------------------------
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; SI7021_PeriodicMeasurement
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;
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; Call this routine periodically to take measurements.
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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SI7021_PeriodicMeasurement:
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in r15, SREG
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push r15
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cli
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lds r17, si7021Flags
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mov r16, r17
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andi r16, SI7021_FLAGS_LASTWASTEMP
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brne si7021PeriodicMeasurement_hum
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ori r17, SI7021_FLAGS_LASTWASTEMP
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sts si7021Flags, r17
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push r17
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rcall si7021MeasureTemp
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pop r17
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brcc si7021PeriodicMeasurement_error
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ori r17, SI7021_FLAGS_TEMP_VALID
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sts si7021Flags, r17
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rcall si7021CalcTemp ; calculate temp*100 from sensor value
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sts si7021LastTemp, r18
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sts si7021LastTemp+1, r19
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rjmp si7021PeriodicMeasurement_done
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si7021PeriodicMeasurement_hum:
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andi r17, ~SI7021_FLAGS_LASTWASTEMP
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sts si7021Flags, r17
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push r17
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rcall si7021MeasureHumidity
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pop r17
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brcc si7021PeriodicMeasurement_error
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ori r17, SI7021_FLAGS_HUM_VALID
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sts si7021Flags, r17
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rcall si7021CalcHumidity
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sts si7021LastHumidity, r18
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sts si7021LastHumidity+1, r19
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si7021PeriodicMeasurement_done:
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pop r15
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out SREG, r15
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sec
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ret
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si7021PeriodicMeasurement_error:
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pop r15
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out SREG, r15
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clc
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ret
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; ---------------------------------------------------------------------------
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; si7021CheckPresence
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;
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; Expects interrupts being disabled!
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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si7021CheckPresence:
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rcall twiStart
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ldi r16, (SI7021_ADDR*2)+1
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rcall twiSendByte
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brcc si7021CheckPresence_notfound
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rcall twiStop
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sec
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ret
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si7021CheckPresence_notfound:
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rcall twiStop
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clc
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ret
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; ---------------------------------------------------------------------------
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; si7021ReadFirmwareRevision
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;
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; Expects interrupts being disabled!
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; Currently doesn't work (my SI7021 doesn't accept the command).
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; - R16: firmware revision (0xff: version 1.0, 0x20: version 2.0)
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; USED:
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si7021ReadFirmwareRevision:
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rcall twiStart
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ldi r16, (SI7021_ADDR*2) ; write access
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rcall twiSendByteExpectAck
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brcc si7021ReadFirmwareRevision_error1
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ldi r16, 0x84
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rcall twiSendByteExpectAck
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brcc si7021ReadFirmwareRevision_error2
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ldi r16, 0xb8
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rcall twiSendByteExpectAck
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brcc si7021ReadFirmwareRevision_error3
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rcall twiRestart
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ldi r16, (SI7021_ADDR*2)+1 ; read access
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rcall twiSendByteExpectAck
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brcc si7021ReadFirmwareRevision_error4
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rcall twiReceiveByte ; don't send ACK
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brcc si7021ReadFirmwareRevision_error5
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rcall twiStop
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sec
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ret
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si7021ReadFirmwareRevision_error1:
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ldi r16, 1
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rcall si7021SetError
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rjmp si7021ReadFirmwareRevision_error
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si7021ReadFirmwareRevision_error2:
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ldi r16, 2
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rcall si7021SetError
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rjmp si7021ReadFirmwareRevision_error
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si7021ReadFirmwareRevision_error3:
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ldi r16, 3
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rcall si7021SetError
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rjmp si7021ReadFirmwareRevision_error
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si7021ReadFirmwareRevision_error4:
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ldi r16, 4
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rcall si7021SetError
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rjmp si7021ReadFirmwareRevision_error
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si7021ReadFirmwareRevision_error5:
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ldi r16, 5
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rcall si7021SetError
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rjmp si7021ReadFirmwareRevision_error
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si7021ReadFirmwareRevision_error:
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rcall twiStop
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clc
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ret
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; ---------------------------------------------------------------------------
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; si7021MeasureTemp
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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si7021MeasureTemp:
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ldi r16, 0xf3
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rjmp si7021MeasureAny
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; ---------------------------------------------------------------------------
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; si7021MeasureHumidity
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;
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; IN:
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; - nothing
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED:
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si7021MeasureHumidity:
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ldi r16, 0xf5
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rjmp si7021MeasureAny
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; ---------------------------------------------------------------------------
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; si7021MeasureAny
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;
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; Sends the given command to the sensor and reads the result.
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; Synchronization is done by sending re-start sequences until the sensor answers with
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; the value.
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; IN:
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; - R16: command to send
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED: R14, R16, R18, R19
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si7021MeasureAny:
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rcall twiStart ; (R22)
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push r16
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ldi r16, (SI7021_ADDR*2) ; write access
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rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
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pop r16
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brcc si7021MeasureAny_error
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rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
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ldi r16, 200
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mov r14, r16
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si7021MeasureAny_loop: ; (R22)
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rcall twiRestart
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ldi r16, (SI7021_ADDR*2)+1 ; read access
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rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
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brcs si7021MeasureAny_gotValue ; chip responds, receive values
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dec r14
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breq si7021MeasureAny_error ; timeout
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Utils_WaitNanoSecs 100000, 0, r22
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rjmp si7021MeasureAny_loop
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si7021MeasureAny_gotValue:
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rcall twiReceiveByteSendAck ; (R16, R17, R18, R22)
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brcc si7021MeasureAny_error
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mov r19, r16 ; MSByte
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rcall twiReceiveByte ; no ACK (R16, R17, R18, R22)
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brcc si7021MeasureAny_error
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mov r18, r16
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rcall twiStop ; (R22)
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ldi r16, 0
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rcall si7021SetError ; (none)
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sec
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ret
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si7021MeasureAny_error:
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rcall twiStop ; (R22)
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clc
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ret
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; ---------------------------------------------------------------------------
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; si7021SetError
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;
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; Set error code in flags.
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; IN:
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; - R16: error code to set (0-7)
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; OUT:
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; - CFLAG: set if okay, clear on error
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; USED: none
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si7021SetError:
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push r17
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lds r17, si7021Flags
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andi r17, ~SI7021_FLAGS_ERROR_MASK
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or r17, r16
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sts si7021Flags, r17
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pop r17
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ret
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; ---------------------------------------------------------------------------
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; si7021CalcTemp
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;
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; Calculates temperatur * 100.
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; Uses formula from specs: temp=(175.72*TEMP_CODE/65536)-46.85.
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;
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; IN:
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; - R19:R18: Temperature value read from sensor
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; OUT:
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; - R19:R18: calculated temperature(Celsius) * 100
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; USED: R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26
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si7021CalcTemp:
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mov r20, r18
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mov r21, r19
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ldi r23, HIGH(17572)
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ldi r22, LOW(17572)
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rcall si7021Mulu16x16_32 ; result is in R19:R18:R17:R16, we only use R19-R18 -> /65536
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ldi r16, LOW(4685)
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ldi r17, HIGH(4685)
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sub r18, r16
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sbc r19, r17
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ret
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; ---------------------------------------------------------------------------
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; si7021CalcHumidity
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;
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; Calculates humidity in percent.
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; Uses formula from specs: rel humidity=(125*HUMIDITY_CODE/65536)-6.
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;
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; IN:
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; - R19:R18: Humidity value read from sensor
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; OUT:
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; - R19:R18: calculated relative humidity
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; USED: R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26
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si7021CalcHumidity:
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mov r20, r18
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mov r21, r19
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clr r23
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ldi r22, 125
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rcall si7021Mulu16x16_32 ; result is in R19:R18:R17:R16, we only use R19-R18 -> /65536
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ldi r16, 6
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clr r17
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sub r18, r16
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sbc r19, r17
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ret
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; ---------------------------------------------------------------------------
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; si7021Mulu16x16_32
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;
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; Multiplies two unsigned 16 bit values resulting in one 32 bit value.
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; This is a rather simple but reasonable fast routine working just like you would
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; when doing multiplications with pen and paper.
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; TODO: adapt for signed values
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;
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; IN:
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; - R21:R20: 16 bit value A
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; - R23:R22: 16 bit value B
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; OUT:
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; - R19:R18:R17:R16: 32 bit result
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; USED: R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26
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; R19:R18:R17:R16 = R21:R20 * R23:R22
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; R19:R18:R17:R16 = R25:R24:R21:R20 * R23:R22
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si7021Mulu16x16_32:
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clr r19
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clr r18
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clr r17
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clr r16
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clr r25
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clr r24
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ldi r26, 16 ; 16 bit multiplicator
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si7021Muls16x16_32_loop:
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lsr r23
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ror r22
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brcc si7021Muls16x16_32_noadd ; current digit in B is 0, don't add shifted A to result
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add r16, r22
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adc r17, r23
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adc r18, r24
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adc r19, r25
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; brcs si7021Muls16x16_32_overflow ; can't happen
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si7021Muls16x16_32_noadd:
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dec r26
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breq si7021Muls16x16_32_done
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lsl r20
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rol r21
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rol r24
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rol r25
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; brcs si7021Muls16x16_32_overflow ; can't happen
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rjmp si7021Muls16x16_32_loop
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si7021Muls16x16_32_done:
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clc
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ret
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;si7021Muls16x16_32_overflow: ; never reached. Multiplying 2 16 bit values can't overflow 32 bit
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; sec
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; ret
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