Please help with code for DS18B20

[Acetronics2]

Hi, Fratello

some homework to do for you ...

take the DS18B20 Datasheet out, and look at :

1) How to get the device ID
2) How to address the device with it's ID

Buuuuuut, I do think ALL the answers you look for already are posted on this Maaarrrrrvellous Forum !!!

It's called SEARCH Function ...

Alain

PS: HELP Function momentarily out of use : New Year update ... lol

[fratello]

I try to read the serial number of my DS18B20 sensor with this code :

TRISA= %11110000 ' RA0..3=Outputs RA4=Input
TRISB= %00000111 ' RB0..RB2=Inputs, RB3..RB7=Outputs
CMCON=7 ' Disable comparators

DEFINE LCD_DREG PORTB ' LCD on port B
DEFINE LCD_DBIT 4 ' Data bits B4..B7
DEFINE LCD_RSREG PORTA ' RS on PORTA
DEFINE LCD_RSBIT 1 ' RS on A1
DEFINE LCD_EREG PORTA ' E on PORTA
DEFINE LCD_EBIT 0 ' E on A0
DEFINE LCD_BITS 4 ' LCD 4 bit mode
DEFINE LCD_LINES 2 ' 2 line LCD display

DQ Var PORTA.4 ' One-wire data pin
i Var Byte
Temp Var Byte
ReadRom Con $33

Pause 500
LCDOUT $FE, 1, $FE, $0C ' Clear display, cursor off
Pause 250

Main

OWOut DQ, 1, [ReadRom]
for i = 0 to 7
OWIn DQ, 0, [Temp]
LcdOut $FE, $80, Hex Temp
Next
LcdOut $FE, $14
LcdOut $FE, $14
Pause 1000
GoTo Main


but on display appears only "A7". What I do wrong ? Thanks !

[Darrel Taylor]

LcdOut $FE, $80, Hex Temp

The $80 moves the cursor to Line1 Column1, and it overwrites the previous values on each loop. All you see is the last loop.
<br>

[fratello]

Per aspera ad astra !!!!
I write another code :

DQ Var PORTA.4 ' One-wire data pin
i Var Byte
Temp Var Byte
ReadRom Con $33
ID VAR BYTE[8] ' Array storage variable for 64-bit ROM code


Begin:
PAUSE 500 ' Wait .5 second
LCDOUT $FE, 1, $FE, $0C ' Clear display, cursor off

Start_Convert
OWOUT DQ, 1, [$33] ' Issue Read ROM command

ID_Loop:
OWIN DQ, 0, [STR ID\8]' Read 64-bit device data into the 8-byte array "ID"
for i = 0 to 7
LcdOut HEX ID[i]
next i
END



Now I have on display : 28CAC648100A7
I think now it is correct. Can You confirm ? Thanks !

[Acetronics2]

Hi, Fratello

Looks fine

my DS shows 7A00000190DF64

read you soon

Alain

[Darrel Taylor]

Almost, but there's not enough digits.

64-bits (8-bytes), will have 16 hex digits.

Try it this way ...

LcdOut HEX2 ID[i]

[fratello]

Thank you all for reply !
In this book : "PIC Microcontrollers: Know It All" from Lucio Di Jasio, Tim Wilmshurst, Dogan Ibrahim, John Morton, Martin Bates, Jack Smith, D.W. Smith, and Chuck Hellebuyck - witch is my inspiration , I read this :
"Dallas Semiconductor’s 1-wire specifications define device serial numbers as 8 bytes (64 bits) long.The family code for 18B20 digital thermometer chips is $28. The CRC (cyclic redundancy code) is an error-checking feature, so that, should we desire, we may verify that the 56 bits of the family code and serial number have been correctly received and were not corrupted. We’ll not further consider how CRCs are calculated, as it’s a topic well beyond the level of this introductory book.
When we run the program, we see the following output:
28 4C D4 3E 0 0 0 D6
...
The digits 4C D4 3E 0 0 0 D6 are, of course, dependent upon the particular DS18B20 chip.
I plugged in a second DS18B20 chip and found its serial number:
28 FE DA 3E 0 0 0 C1
In the output, $28 is the family number and $D6 (or $C1 in the second example) is the CRC. The center six bytes represent the serial number of the chip. But, here’s a difference between the result and the serial number specification isn’t there? The definition has the CRC sent first and the family code sent last. Yet, Program 22.1 displays the family code first, and the CRC last.The explanation is that 1-wire devices store the least significant byte at the lower address and
the most significant byte at the higher address. Bytes are transmitted and received from lowest address to highest address. Hence, the net effect is the send/receive byte order is reversed from the data sheet description. This is more confusing to describe than to use; when we wish to address a particular device, we just repeat the byte order we read with Program 22.1"

So, I think it is enough for me these results.
Next step is : Reading multiple sensors on the same bus.
... Wish me luck !
I will keep you informed and - hope- I will receive yours advices again.
All the best !

[Acetronics2]

Hi, Fratello

From the Datasheet Organigrams ... you'll see the Bytes Order is inverted ...

as you worked Well ...

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

  OWOUT DQ, 1, [ $33 ]								' Read Chip code
  OWIN  DQ, 2, [ FAM,ID[6],ID[5],ID[4],ID[3],ID[2],ID[1],CRC]
  
  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"
  	
  	PAUSE 1000
  	
  	LCDOUT $FE,$80, 				" CRC: ",HEX2 CRC," FAM: ", HEX2 FAM
  	
  ENDIF
  	  	
  IF FAM = $28 THEN
  
   	LCDOUT $FE,$80, 				"DS 18B20     " 
   	
 	OWOUT DQ, 1, [$CC, $4E, 0, 0, DS18B20_11bit]    '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]

Here Data are shown with their signification ... Hope it will help

Alain