Is there a way to see if a DS18B20 is present

[Kmt]

Hi

I have to know if a DS18B20 is "brokken" missing, so is there a way to see this?

I have try this but is just say "yes a sensor" even if I have taken the DS18B20 of?

check_sensor:

Low comm_pin1 'Set the data pin low to initialize
PauseUs 500 'Wait for more than 480us
TRISA.0=1 'Release the data pin (set to input for high)
PauseUs 100 'Wait for more than 60us
IF comm_pin1=1 Then
LcdOut $FE, $1, " NO " ' Show message
Lcdout $fe, $c0, " sensor "
pause 2000
Else
LcdOut $FE, $1, " yes a " ' Show message
Lcdout $fe, $c0, " sensor "
pause 2000
EndIF
return

Kent

[Acetronics2]

the only way is to read the sensor chip ID ...

something like that:


'************************************************* ****************************
SensID:' Sensor Identification
'************************************************* ****************************

OWOUT DQ, 1, [ $33 ] ' Read Chip Family code
OWIN DQ, 2, [ FAM,ID[6],ID[5],ID[4],ID[3],ID[2],ID[1],CRC]

' PAR Device ???
OWOut DQ, 1, [$55, FAM,ID[6],ID[5],ID[4],ID[3],ID[2],ID[1],CRC, $44 ]
OWOut DQ, 1, [ $55, FAM,ID[6],ID[5],ID[4],ID[3],ID[2],ID[1],CRC, $BE ]
PAUSE 750
OWIN DQ, 2, [R_Temp.Lowbyte, R_Temp.Highbyte] ' Read two bytes

IF FAM != $FF THEN

IF R_Temp = $0550 OR R_Temp = $AA THEN

PAR = 1

ELSE

PAR = 0

ENDIF

ELSE

LCDOUT $FE,$80, "NO SENSOR "
LCDOUT $FE,$C0, "Chk Sens & Reset"
STOP

ENDIF

IF FAM = $05 THEN

LCDOUT $FE,$80, "DS 2405 "

PAUSE 1000

LCDOUT $FE,$80, " CRC: ",HEX2 CRC," FAM: ", HEX2 FAM

ENDIF

IF FAM = $10 THEN

LCDOUT $FE,$80, "DS 18S20/1820"
IF PAR THEN LCDOUT $FE,$88," PAR " : PAUSE 1000

Tempo = 250
PAUSE 1000

LCDOUT $FE,$80, " CRC: ",HEX2 CRC," FAM: ", HEX2 FAM

ENDIF

IF FAM = $22 THEN

LCDOUT $FE,$80, "DS 1822 "
IF PAR THEN LCDOUT $FE,$88," PAR " : PAUSE 1000

OWOUT DQ, 1, [$CC, $4E, 0, 0, DS18B20_bit] 'Skip ROM search and write N_bits
' resolution to scratch pad
PAUSE 1000

LCDOUT $FE,$80, " CRC: ",HEX2 CRC," FAM: ", HEX2 FAM

ENDIF

IF FAM = $28 THEN

LCDOUT $FE,$80, "DS 18B20 "
IF PAR THEN LCDOUT $FE,$88," PAR " : PAUSE 1000

OWOUT DQ, 1, [$CC, $4E, 0, 0, DS18B20_bit] 'Skip ROM search and write N_bits
' resolution to scratch pad
PAUSE 1000

LCDOUT $FE,$80, " CRC: ",HEX2 CRC," FAM: ", HEX2 FAM

ENDIF



LCDOUT $FE,$C0," ID:",HEX2 ID[1],HEX2 ID[2],HEX2 ID[3],HEX2 ID[4],HEX2 ID[5],HEX2 ID[6]



Alain

[Kmt]

Thanks Alain

This give me some things to work with, And I got it now :)

I look at the ID if all is 0 the no sensor.

Kent

[Hebemabo]

This I use and it works well:


Start:

OWOUT DQ, 1, [ $33 ] 'send read Rom command

OWIN DQ, 2, [ FaM,skip 7] 'read sensor family code, skip ID and CRC
if FaM = $28 then SkipOver 'if FaM = 28 then sensor is present

LCDOUT $FE,$80, "NO SENSOR "
LCDOUT $FE,$C0, "Chk Sens & Reset"

goto Start 'sensor not present so do again

SkipOver: 'continue your code here

Regards
Hebe