Hi,
I need to interface a one-wire temperature sensor DS1820. I found some MSP430 asm examples (TI source code below). I generally code in C.
What's your opinion : Is that easier to convert the asm code below to work with Piccolo Microcontroller or restart a new base in C.
Are the assembly command identical between MSP430 and TMS320 microcontroller ?
Thanks for your inputs
;*******************************************************************************
; MSP430x11x1 Demo - Software 1-Wire Interface DS1820, .set P1.0 if > 30C
;
; Description: 1-wire communication with DS1820 temperature sensor is
; demonstrated. If temperature read > 30.0c (01E0h), P1.0 is set, else reset.
; Default 12-bit temperature mode read as two bytes and packed into DATA1W.
; Only two byte temperature data is read from DS1820, balance of DS1820
; scratchpad is ignored. 1-wire timing is important and the software is
; written assuming MCLK ~800kHz. Normal mode is LPM3 with WDT triggering
; measurement interval every 1s.
; ACLK = LFXT1 = 32768, MCLK = SMCLK = default DCO ~800k
; ;* External watch crystal installed on XIN XOUT is required for ACLK *//
;
; MSP430F1121
; /|\ /|\ -----------------
; | DS1820 4.7k| XIN|-
; | ------- | | | 32kHz
; ---|VDD DQ|<-----+->|P2.0 XOUT|-
; ---|GND | | |
; \|/ ------- | P1.0|-->LED
;
;
; CPU registers used
DATA1W .equ R4
BIT1W .equ R5
;
; Definitions for 1-wire bus
DQ .equ 001h ; P2.0 controls DQ line (pull-up)
;
; M. Buccini / Z. Albus
; Texas Instruments Inc.
; May 2005
; Built with Code Composer Essentials Version: 1.0
;*******************************************************************************
.cdecls C,LIST, "msp430x11x1.h"
;-------------------------------------------------------------------------------
.text ; Program Start
;-------------------------------------------------------------------------------
RESET mov.w #300h,SP ; Initialize stackpointer
Setup mov.w #WDT_ADLY_1000,&WDTCTL ; WDT 1s, ACLK, interval timer
bis.b #WDTIE,&IE1 ; Enable WDT interrupt
SetupP1 bis.b #001h,&P1DIR ; P1.0 output
SetupP2 bic.b #001h,&P2OUT ; Make sure P2.0 output latch = 0
;
Mainloop bis.w #LPM3+GIE,SR ; Enter LPM3 w/ interrupts
call #Reset_1W ; DS1820 Reset
mov.b #0CCh,DATA1W ; DS1820 command to skip ROM
call #Write_1W ;
mov.b #044h,DATA1W ; DS1820 comand to convert temp
call #Write_1W ;
;
call #Reset_1W ; DS1820 Reset
mov.b #0CCh,DATA1W ; DS1820 command to skip ROM
call #Write_1W ;
mov.b #0BEh,DATA1W ; DS1820 command to read scratchpad
call #Write_1W ;
call #Read_1W ; DS1820 LSB read
push.w DATA1W ; TOS = 00|LSB
call #Read_1W ; DS1820 LSB read
swpb DATA1W ; DATA1W = MSB|00
add.w @SP+,DATA1W ; DATA1W = MSB|LSB
;
Temp_test bic.b #01h,&P1OUT ; P1.0 = 0
cmp.w #01E0h,DATA1W ; DATA1W > 30.0c?
jlo Mainloop ; Again
bis.b #01h,&P1OUT ; P1.0 = 1
jmp Mainloop ; Again
;
;-------------------------------------------------------------------------------
Reset_1W; Subroutine to Reset 1-wire device and detect presence
;-------------------------------------------------------------------------------
bis.b #DQ,&P2DIR ;
mov #240,R15 ; ~ 720us delay
call #Delay_R15 ;
bic.b #DQ,&P2DIR ;
call #Delay_60us ; ~ 60us delay subroutine
Rxx bit.b #DQ,&P2IN ; Check for presence
jc Rxx ;
;
mov #160,R15 ; ~ 480us Delay
call #Delay_R15 ;
ret ;
;
;-------------------------------------------------------------------------------
Write_1W; enter DATA1W = 00 - FF 1-wire data to write
; BIT1W = xx
;-------------------------------------------------------------------------------
mov.w #8h,BIT1W ;
TX_1W_Bit rrc.b DATA1W ;
jc TX_1W_1 ;
TX_1W_0 bis.b #DQ,&P2DIR ;
call #Delay_60us ; ~ 60us delay subroutine
bic.b #DQ,&P2DIR ;
jmp TX_1W_x ;
TX_1W_1 bis.b #DQ,&P2DIR ;
bic.b #DQ,&P2DIR ;
call #Delay_60us ; ~ 60us delay subroutine
TX_1W_x dec.w BIT1W ;
jnz TX_1W_Bit ;
ret ;
;
;-------------------------------------------------------------------------------
Read_1W; enter DATA1W = xx
; BIT1W = xx
; exit DATA1W = 00 - FF 1-wire data read
; BIT1W = xx
;-------------------------------------------------------------------------------
mov.w #8h,BIT1W ;
RX_1W_Bit bis.b #DQ,&P2DIR ;
bic.b #DQ,&P2DIR ;
nop ;
nop ;
bit.b #DQ,&P2IN ;
rrc.b DATA1W ;
call #Delay_60us ; ~ 60us delay subroutine
dec.w BIT1W ;
jnz RX_1W_Bit ;
ret ;
;
;-------------------------------------------------------------------------------
Delay_60us mov.w #20,R15
;-------------------------------------------------------------------------------
Delay_R15 dec.w R15 ;
jnz Delay_R15 ;
ret ;
;
;-------------------------------------------------------------------------------
WDT_ISR ; Exit LPM3 on reti
;-------------------------------------------------------------------------------
bic.w #LPM3,0(SP) ; Clear LPM3 from TOS
reti ;
;
;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
.sect ".reset" ; MSP430 RESET Vector
.short RESET ;
.sect ".int10" ; WDT Vector
.short WDT_ISR ;
.end
