LCD temperature display

[sambo77]

Hi everyone,

I'm building a temperature controller which requires temperature readout on an LCD display. I am using an 18X with ds18b20 sensors and a 40x2 display.

I have the hardware setup and working fine with the LCD interface as per Hippy's instructions at http://http://www.hippy.freeserve.co.uk/picaxelc.htm

I can get plain text stored in EEPROM to display on the LCD fine, but I am not sure how to display variables produced by the readtemp command.

Here is the code I am using to drive the LCD:

SYMBOL RS = 2 ; 0 = Command 1 = Data
SYMBOL E = 3 ; 0 = Idle 1 = Active
SYMBOL DB4 = 4 ; LCD Data Line 4
SYMBOL DB5 = 5 ; LCD Data Line 5
SYMBOL DB6 = 6 ; LCD Data Line 6
SYMBOL DB7 = 7 ; LCD Data Line 7

SYMBOL RSCMDmask = %00000000 ; Select Command register
SYMBOL RSDATmask = %00000100 ; Select Data register

SYMBOL get = b11
SYMBOL byte = b12
SYMBOL rsbit = b13

PowerOnReset:

GOSUB InitialiseLcd

DisplayTopLine:

EEPROM 6,("Hello")

FOR get = 6 TO 10
READ get,byte
GOSUB SendDataByte
NEXT

MoveCursorToStartOfSecondLine:

byte = $C0
GOSUB SendCmdByte

DisplayBottomLine:

EEPROM 11,("World!")

FOR get = 11 TO 16
READ get,byte
GOSUB SendDataByte
NEXT

END

InitialiseLcd:

FOR get = 0 TO 5
READ get,byte
GOSUB SendInitCmdByte
NEXT

' Nibble commands - To initialise 4-bit mode

EEPROM 0,( $33 ) ; %0011---- %0011---- 8-bit / 8-bit
EEPROM 1,( $32 ) ; %0011---- %0010---- 8-bit / 4-bit

' Byte commands - To configure the LCD

EEPROM 2,( $28 ) ; %00101000 %001LNF00 Display Format
EEPROM 3,( $0C ) ; %00001100 %00001DCB Display On
EEPROM 4,( $06 ) ; %00000110 %000001IS Cursor Move

; L : 0 = 4-bit Mode 1 = 8-bit Mode
; N : 0 = 1 Line 1 = 2 Lines
; F : 0 = 5x7 Pixels 1 = N/A
; D : 0 = Display Off 1 = Display On
; C : 0 = Cursor Off 1 = Cursor On
; B : 0 = Cursor Steady 1 = Cursor Flash
; I : 0 = Dec Cursor 1 = Inc Cursor
; S : 0 = Cursor Move 1 = Display Shift

EEPROM 5,( $01 ) ; Clear Screen

RETURN

SendInitCmdByte:

PAUSE 15 ; Delay 15mS

SendCmdByte:

rsbit = RSCMDmask ; Send to Command register

SendDataByte:

pins = byte & %11110000 | rsbit ; Put MSB out first
PULSOUT E,1 ; Give a 10uS pulse on E
pins = byte * %00010000 | rsbit ; Put LSB out second
PULSOUT E,1 ; Give a 10uS pulse on E

rsbit = RSDATmask ; Send to Data register next

RETURN

Could someone show me what changes I need to make to display temperature values acquired by readtemp?

Thanks for your help,
Sam

 

[westaust55]

Welcome to the PICAXE forum.
If you are expecting negative values as well as positive then you will need to check for the sign as well.

SYMBOL sign = b2
:
:
Sign = “ “
IF temp > 127 THEN
sign = “+”
ENDIF
byte = sign
GOSUB  SendDataByte
If temp > 100
Byte = temp / 100 + $30
Else 
bytes = “ “
ENDIF
GOSUB  SendDataByte
If temp > 10
Byte = temp // 100 / 10 + $30
ELSE
Byte = “ “
GOSUB  SendDataByte
Byte = temp // 10 + $30
GOSUB  SendDataByte

EDIT: The above is the long hand way and shows you how to extract each digit and use a leading blank when here are less that 3 digits.
Also have a look at the BINTOASCII command in PICAXE manual 2
That can save you some of the above maths and also the need to add $30 to each value sent to create the ASCII code equivalent for each digit.

 

[sambo77]

Thanks for your help westaust55, got it working! i kind of threw myself into the deep end not having any experience with the picaxe programming, still a bit to learn! will also try out the bintoascii command as you suggested

 

[westaust55]

great to read that you got your project going.

Always a sense of achievement when somethings works