Post by thread:[PIC]: I2C Master Mode Read

Hello All I have an AD5321 that is connected to a 16F873A via the MSSP module. I have the PIC writing data to the D/A. The PIC is in Master Mode. To start a read of the AD5321 I must send it a byte, b"00011111", then wait for a acknowledge state from the AD5321 by it pulling down the SCL line. Then it will send me the MSB of my data and wait on a acknowledge state from the PIC (Pulling SCL low) then send the LSB and then there should be no acknowledge from the PIC and a stop condition generated by the PIC. Here is my code that I have tried to implement it with. This does not include the MSSP set up code. Comments were removed to save space. What is wrong with my implementation? Chuck Roberts DISABLE_IRQ BANK1 BSF SSPCON2,SEN BANK0 BTFSS PIR1,SSPIF GOTO $-1 BCF PIR1,SSPIF BANK0 MOVLW DA_ADDRESS2 MOVWF SSPBUF BTFSS PIR1,SSPIF GOTO $-1 BCF PIR1,SSPIF BANK1 BSF SSPCON2,PEN BANK0 BTFSS PIR1,SSPIF GOTO $-1 BCF PIR1,SSPIF BANK1 BSF SSPCON2,RCEN BANK0 BTFSS PIR1,SSPIF GOTO $-1 BCF PIR1,SSPIF BANK1 BTFSS SSPSTAT,BF GOTO $-1 BANK0 MOVF SSPBUF,W MOVWF DAC_RH BANK0 BTFSS PIR1,SSPIF GOTO $-1 BCF PIR1,SSPIF BANK1 BTFSS SSPSTAT,BF GOTO $-1 BANK0 MOVF SSPBUF,W MOVWF DAC_RL BANK0 ENABLE_IRQ RETURN

On 12/27/05, Roberts II, Charles K. <spam_OUTrobertsckTakeThisOuTornl.gov> wrote: <snip> > Comments were removed to save space. > What is wrong with my implementation? Chuck Roberts I'm sure you'll get other comments like this, but your code is infinitely harder to read without comments. Heck, unless they have a familiar coding style, I find other people's code _with_ comments can get difficult at times. Unless you wrote a book in your comments, include them. At the very least I've seen numerous times where someone will say what they want to do in the comments, but there is a typo in the actual code. With your post, I have no idea what you're expecting to do with the code. Just some advice! Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams

This code is designed to read the status and settings of the AD5321 D/A. And write the two data bytes to DAC_RL,DAC_RH. The macro's and initialization code come from the Tony Kübek full initialization code on the PIC list site. This code is not reading back any values. The read process was described in my first email. What am I doing wrong in the implementation of the read process? Chuck READ_DAC_DIRECT DISABLE_IRQ ;MACRO to disable global interrupt BANK1 ;MACRO to change bank settings BSF SSPCON2,SEN ;set start bit BANK0 BTFSS PIR1,SSPIF ; wait for interrupt flag to be set TEST!! GOTO $-1 BCF PIR1,SSPIF BANK0 MOVLW DA_ADDRESS2 MOVWF SSPBUF ;send out the address ; wait for the write to complete before we return BTFSS PIR1,SSPIF ; wait for interrupt flag to be set GOTO $-1 BCF PIR1,SSPIF ;clear irq flag BANK1 BSF SSPCON2,PEN ;set stop bit BANK0 BTFSS PIR1,SSPIF ; wait for interrupt flag to be set TEST!! GOTO $-1 BCF PIR1,SSPIF ;******************************************************************* ;This portion of the code will read the data from the DAC ;will write data to DAC_RH and DAC_RL ; ; BANK1 BSF SSPCON2,RCEN ;enables read BANK0 ; wait for the write to complete before we return BTFSS PIR1,SSPIF ; wait for interrupt flag to be set GOTO $-1 BCF PIR1,SSPIF ;clear irq flag BANK1 BTFSS SSPSTAT,BF ;Checks if read buffer is full GOTO $-1 BANK0 MOVF SSPBUF,W ;reads contents of buffer MOVWF DAC_RH ;writes to register to pass out of routine ; wait for the write to complete before we return BTFSS PIR1,SSPIF ; wait for interrupt flag to be set GOTO $-1 BCF PIR1,SSPIF ;clear irq flag BANK1 BTFSS SSPSTAT,BF ;Checks if read buffer is full GOTO $-1 BANK0 MOVF SSPBUF,W ;reads contents of buffer MOVWF DAC_RL ;writes to register to pass out of routine ENABLE_IRQ RETURN ; and return

Roberts II, Charles K. wrote: > What am I doing wrong in the implementation of the read process? I was going to reply in line with your code, but you put tab characters in the code so it looked like a mess on my screen. I think your address byte is wrong, but I didn't look at the code closely because it was too much of a mess. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products