;******************************************************************************
;  MSP430F20xx Demo - I2C Master Transmitter and Receiver
;
;  Description: MSP430 I2C Master communicates with MSP430 I2C Slave using
;  the USI module. 
;  The master device transmits 16 bytes of data to the slave device and reads 
;  it back. LED turns on if transmitted data = received data.
;  Slave MSP430 device must be enabled connected to the bus before master 
;  begins first transmit operation.
;  ACLK = n/a, MCLK = SMCLK = Calibrated 1MHz
;
;  ***THIS IS THE MASTER CODE***
;
;                  Slave                      Master
;          (example_slave430interface.s43)
;               MSP430F20x2/3              MSP430F20x2/3
;             -----------------          -----------------
;         /|\|              XIN|-    /|\|              XIN|-
;          | |                 |      | |                 |
;          --|RST          XOUT|-     --|RST          XOUT|-
;            |                 |        |                 |
;      LED <-|P1.0             |        |                 |
;            |                 |        |             P1.0|-> LED
;            |         SDA/P1.7|------->|P1.7/SDA         |
;            |         SCL/P1.6|<-------|P1.6/SCL         |
;
;  Note: Internal pull-ups are used in this example for SDA & SCL
;        MSP430 Slave address = 0x48
;
;  P. Thanigai
;  Texas Instruments Inc.
;  August 2007
;  Built with IAR Embedded Workbench Version: 3.41A
;******************************************************************************
#include  <msp430x20x2.h>
EXTERN    TI_USI_I2C_MasterInit
EXTERN    TI_USI_I2CRead
EXTERN    TI_USI_I2CWrite
EXTERN    TI_USI_I2CSelect

            RSEG    DATA16_C
Transmit    DB      0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07
            DB      0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,0x0F   
            RSEG    DATA16_N
Receive     DS      16             

;-------------------------------------------------------------------------------
            RSEG    CSTACK                  ; Define stack segment
;-------------------------------------------------------------------------------
            RSEG    CODE                    ; Assemble to Flash memory
            EVEN
;-------------------------------------------------------------------------------
RESET       mov.w   #SFE(CSTACK),SP         ; Initialize stackpointer
StopWDT     mov.w   #WDTPW+WDTHOLD,&WDTCTL  ; Stop WDT
SetupDCO    mov.b   &CALBC1_1MHZ,&BCSCTL1   ; Load DCO calibration constants  
            mov.b   &CALDCO_1MHZ,&DCOCTL  
SetupPx     bis.b   #0x03,&P1DIR            ; P1.0& 1.1 as output
InitCall    mov.b   #0xEA,R12               ; USIDIV_7+USISSEL_2+USICKPL
            mov.w   #StatusCallback,R14     ; Callback fn. pointer
            call    #TI_USI_I2C_MasterInit
SlaveDetect            
            xor.b   #0x01,&P1OUT            ; Detect if slave is present...
            mov.w   #0xFFFF,R5              ; ... LED toggles until slave ACKS
L1          dec.w   R5
            jnz     L1 
Poll_0      call    #AcknowledgePoll        ; Slave device present?
            cmp.b   #0,R12                  ; Is result zero (ACK)?
            jnz     SlaveDetect             ; Loop until device acknowledges
            clr.b   &P1OUT                  ; Slave acknowledged, LED off 
TransmitCall
            mov.w   #0x48,R12               ; Slave address
            mov.w   #0x10,R14               ; length = 16
            push.w  #Transmit               ; pointer to data buffer 
            push.w  #0x00                   ; multi parameter
            call    #TI_USI_I2CWrite        ; Call transmit fn.
            add.w   #4,SP                   ; compensate SP on return
            bis.w   #LPM0+GIE,SR            ; enter LPM, enable interrupts 
            nop             
ReceiveCall  
            mov.w   #0x48,R12               ; Slave address
            mov.w   #0x10,R14               ; length = 16
            push.w  #Receive                ; pointer to data buffer
            push.w  #0x00                   ; multi
            call    #TI_USI_I2CRead         ; Call receive fn.
            add.w   #4,SP                   ; compensate SP on return
            bis.w   #LPM0+GIE,SR            ; enter LPM, enable interrupts 
CheckResult            
            mov.w   #Receive,R6             ; chk received data
            mov.w   #Transmit,R4
            clr.w   R5
Compare     cmp.b   @R4,0(R6)
            jz      Increment  
            clr.b   &P1OUT
            jmp     EndProgram
Increment   
            inc.w   R4
            inc.w   R6
            inc.w   R5
            cmp.b   #0x0F,R5                ; counter =16?
            jnz     Compare                 ; if all 16 bytes are correct...
            bis.b   #0x01,&P1OUT            ; ... turn on LED
EndProgram  jmp     $                       ; program ends here
AcknowledgePoll           
            mov.b   #0x48,R12               ; slave address
            call    #TI_USI_I2CSelect       ; Ack polling function
            ret
StatusCallback
            mov.w   #1,R12                  ; wake up on exit
            ret

;-------------------------------------------------------------------------------
            COMMON  INTVEC                  ; Interrupt Vectors
;-------------------------------------------------------------------------------
            ORG     RESET_VECTOR            ; POR, ext. Reset
            DW      RESET                   ;
            END