interfaceing pic16f877, lcd & rtc ds1307

DS1307_init

call StartI2C ; Set SSPCON2.SEN
bcf I2C_Ctrl,0 ; set for write Command
movf I2C_Ctrl,W ; Send Slave Address to i2C Bus
call Send_Byte

movlw 0x00 ; 00H address
call Send_Byte

movlw B'00000000' ; clk_halt bit disabled
call Send_Byte

movlw 0x02 ; 02H address 12/24 hrs format
call Send_Byte

movlw B'00000000' ; 24 hrs mode setting
call Send_Byte

movlw 0x07 ; 07H address SQWE /RS0/RS1 call Send_Byte

movlw B'00010000' ; sqwe enable at 1Hz
call Send_Byte

call StopI2C ; Initial STOP Condition

return


Sir=,
Is this the correct i2c code for setting ds1307 rtc. If wrong please tell me where I am wrong.
1. I have started i2c by "StartI2C"
2.Next send the device id with a write flag.
3.Send the address of the rtc
4. Send the data to be filled in that address.
5.Stop the i2c

Should i restart after every address access, or should i send a nAck after each access. I am confused how to access individual address and fill data in it.
Please help

Hi,


The i2c routine can be difficult to get going.

Here is a complete working project , author unknown.

It should be very easy to convert to a 877, if you have proteus you can see this project working using the .dsn file.

Sir, I am not able to get even the first acknowlege (ACKSTAT=0) after a address send

call StartI2C ; Set SSPCON2.SEN

bcf I2C_Ctrl,0 ; Clear for Write Command
movf I2C_Ctrl,W ; Send Slave Address to I2C Bus
movlw 0xD0 ;address id of ds1307
call Send_Byte
; **an ACSTAT test fails , the bit is = 1

Please suggest what to do, I have even changed the rtc.

Hi,

Have a look at this i2ctutorial which includes a similar rtc
PIC Tutorial* Six - I2C EEPROM Programming