[问答]

I2C通信：18F4550和DS1307 RTC

问答对人有帮助，内容完整，我也想知道答案 0 嗨，我用I2C解决问题的小贡献：在PIC18F450主控和从机RTC DS1307.RB0和RB1之间进行I2C通信的汇编代码是SDA和SCL线，不要忘记在两条线路上加上上拉电阻1-4、7K。以上来自于百度翻译以下为原文 Hi, my little contribution to solving problems with I2C: tested assembly code for I2C communication between master PIC18F4550 and slave RTC DS1307. RB0 and RB1 are SDA and SCL lines, do not forget to put pull-up resistors 1-4,7k on both lines. ;RTC DS1307: #define SDA PORTB,0 ;SDA for DS1307 #define SCL PORTB,1 ;SCL fot DS1307 ;**************************************************************************** ; DS1307 RTC SUBROUTINES *** ;************************************************************************** INIT_I2C ;MASTER MODE initialization for I2C port: movlw d'19' ;Baud Rate Generator for 8MHz & 100kHz = d'19' movwf SSPADD ; I2C movlw B'11000000' ; movwf SSPSTAT movlw b'00101000' ;master mode movwf SSPCON1 movlw b'00000000' ; movwf SSPCON2 ; I2C call WRITE_CONTROL_REG call WRITE_CH_0 ;to enable internal oscilator return ;****************************************************************** WRITE_CONTROL_REG ;write new value to control register: call START_BIT movlw h'D0' ;I2C address of DS1307 call WRITE_I2C ; I2C movlw h'07' ;control register address call WRITE_I2C movlw b'10010000' ;new value of control register call WRITE_I2C ; I2C call STOP_BIT return ;****************************************************************** WRITE_CH_0 ;write 0 to CH-bit in addr. 00 to new DS1307 call READ_TIME_DS1307 btfss SECOND,7 return call START_BIT movlw h'D0' ;I2C address of DS1307 call WRITE_I2C ; I2C movlw h'00' ;address 00 of seconds call WRITE_I2C movlw b'00000000' ;new value to seconds register call WRITE_I2C call STOP_BIT ; I2C return ;****************************************************************** READ_TIME_DS1307 ;read all time registers from DS1307 ;set register pointer to 0: call START_BIT ; movlw h'D0' ;I2C address of DS1307 call WRITE_I2C movlw 0x00 ;start address call WRITE_I2C call STOP_BIT ;read all data from DS1307: call START_BIT movlw 0xD1 ;I2C address of DS1307 + READ bit call WRITE_I2C RX_SEC call READ_I2C ; I2C movwf SECOND ;save seconds RX_MIN call READ_I2C movwf MINUTE ;save minutes RX_HOUR call READ_I2C movwf HOUR ;save hours RX_DAY call READ_I2C ; I2C movwf DAY ;save day RX_DATE call READ_I2C movwf DATE ;save date RX_MONTH call READ_I2C ; I2C movwf MONTH ;save month RX_YEAR call LAST_READ_I2C movwf YEAR ;save year call STOP_BIT return ;***************************** WRITE_TO_DS1307 ;write new time values to DS1307: call START_BIT movlw h'D0' ;I2C address of DS1307 call WRITE_I2C ; I2C movlw h'01' ;first register address call WRITE_I2C movlw b'01000110' ;new BCD minute value call WRITE_I2C ; I2C movlw b'00100000' ;new BCD hour value call WRITE_I2C ; I2C ;.... ;.... call STOP_BIT return ;************************************************************************** ;send 1 byte through I2C: WRITE_I2C movwf SSPBUF ; I2C call WAIT_MSSP retlw h'00' ;***************************** ;receive 1 byte through I2C + ACK: READ_I2C btfsc SSPSTAT,2 goto READ_I2C ; I2C bsf SSPCON2,RCEN call WAIT_MSSP bcf PIR1,SSPIF ; I2C call ACK_BIT movf SSPBUF,W ; I2C return ;***************************** ;receive last byte through I2C + NACK: LAST_READ_I2C btfsc SSPSTAT,2 goto LAST_READ_I2C ; I2C bsf SSPCON2,RCEN call WAIT_MSSP bcf PIR1,SSPIF call NACK_BIT ; I2C movf SSPBUF,W return ;***************************** START_BIT bsf SSPCON2,SEN call WAIT_MSSP ; I2C retlw h'00' ;***************************** STOP_BIT bsf SSPCON2,PEN call WAIT_MSSP ; I2C retlw h'00' ;***************************** ACK_BIT bcf SSPCON2,ACKDT bsf SSPCON2,ACKEN call WAIT_MSSP ; I2C retlw h'00' ;***************************** NACK_BIT bsf SSPCON2,ACKDT bsf SSPCON2,ACKEN call WAIT_MSSP ; I2C retlw h'00' ;***************************** WAIT_MSSP btfss PIR1,SSPIF ; I2C goto WAIT_MSSP bcf PIR1,SSPIF retlw h'00' ;**************************************************************************** 0
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答案对人有帮助，有参考价值 0 谢谢你的贡献。在每次写之后检查ACK位是个好主意，尤其是当你发送从地址时。以上来自于百度翻译以下为原文 Thanks for contributing. It would be a good idea to check the ACK bit after each write, particularly when you send the slave address.

2018-11-28 16:47:49 评论举报吴键洪