Unable to read data from I2C?

Question

I am interfacing DS1307 with PIC32MX795F512L using peripheral library. I am able to send data but not able to receive it.

Code:

#include <plib.h>
#define BAUDRATE 115200
#define Fsck 100000
#define BRG ((FPB/2/Fsck)-2)
#define FCY 66000000L
#define FPB (FCY/2)
#pragma config POSCMOD=HS, FNOSC=PRIPLL 
#pragma config FPLLIDIV=DIV_3, FPLLMUL=MUL_18, FPLLODIV=DIV_1 
#pragma config FPBDIV=DIV_2, FWDTEN=OFF 
#pragma config FSOSCEN = OFF 
#pragma config ICESEL = ICS_PGx2
int main(int argc, char** argv)
{
 OpenUART1( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT , UART_RX_ENABLE | UART_TX_ENABLE, (FPB/16/BAUDRATE)-1 );
putsUART1("START\n");
int res;
OpenI2C2(I2C_EN, 163); // I2C channel Configuration
StartI2C2();
IdleI2C2();
MasterWriteI2C2(0xD0); 
Nop();
MasterWriteI2C2(0x01); 
Nop();
MasterWriteI2C2(0b00010011); 
Nop();
StopI2C2();
IdleI2C2(); 
StartI2C2();
IdleI2C2(); 
MasterWriteI2C2(0xD0);
Nop();
MasterWriteI2C2(0x01);
Nop();
StopI2C2();
RestartI2C2();
IdleI2C2();
MasterWriteI2C2(0xD1);
Nop();
MasterWriteI2C2(0x01);
IdleI2C2();
res = MasterReadI2C2();
Nop();
NotAckI2C2();
Nop();
StopI2C2();
 //converting to ASCII
unsigned char x,y,p1,p2;
x = res & 0x0F;
p1 = x | 0x30;
y = res & 0xF0;
y = y >> 4;
p2 = y | 0x30;
char value1[5] ;
char value2[5] ;
sprintf(value1,"%d",p1);
sprintf(value2,"%d",p2);
putsUART1(value1);
putsUART1(value2);
putsUART1("\n");
while(1)
{
}
return (EXIT_SUCCESS);
}

UART is working fine and there is no collision because the function MasterWriteI2C2() returns -1 if there is collision and returns 0 if there is no collision and data transmission is successful & I have received 0, that means data is being transmitted but I don't know why its not able to read back data. Please help.

EDIT:

I resolved the problem which I was facing and now I2C is working as I can see the received value in I2CRCV register is same which I am sending. But I need to send the value to UART for which I think I need to convert them to ASCII but after converting the values will change. Lets say I have set 13 value in seconds register then its value will change during conversion, then how can I set RTC value. I need to make a logic so that I can set the RTC value from UART. Please help.!

• Cabs: I don't understand : "I am able to send data but not able to receive it. I am receiving the data on UART so also converting it into ASCII, I receive 48 which is 0." Do you receive the data in UART? And you don't in I2C?
• user007: I mean to say I am trying to get data from I2C and then transmitting it serially but on serial I am receiving 0
• damien: Did you look on an oscilloscope if there was data on the SDA line? The data sended seems ok to me then it could come from different problem: 1) Timing, your nop may not be enought time there is function given by microchip to wait until the I2C has start or the I2C is IDLE and so on. 2) The hardware, that can come from the resistors on the I2C line. Also I don't get why you don't ack I2C at the end of the read.
• user007: I don't have oscilloscope so can't check with it. Earlier I was using IdleI2C() which wait for the bus to be Idle, but it was still the problem, so I thought of using Nop(). On the hardware, there is 1k resistors on I2C line.
• efox29: @user007 Sounds like this question should be closed since you have said you resolved it. If you have another question, create a new question. Don't add unrelated topics in the same question.

Answer 1

I didn't wade thru your code, but one obvious problem pops out immediately.

You don't use a UART to do IIC. Note the "A" in UART stands for "asynchronous", which IIC is definitely not.

To do IIC, use the IIC peripheral or do it all in firmware. That's actually quite easy when you're the master since you own the clock.

• PeterJ: I think the mention of the UART working is how the debug information is being returned, it appears the OpenI2C2 etc is the I2C code.
• Scott Seidman: ...unless the device tries to stretch the clock.
• user007: I resolved the problem which I was facing and now I2C is working as I can see the received value in I2CRCV register is same which I am sending. But I need to send the value to UART for which I think I need to convert them to ASCII but after converting the values will change. Lets say I have set 13 value in seconds register then its value will change during conversion, then how can I set RTC value. I am confused.!