PIC32MM0256GPM064 interface with MCP7940N RTC using I2C communication

[Dakshata]

I am trying to communicate between pic32 to RTC using i2c communication , but i have only received lowest nibble value and highest nibble value not proper received .
it means suppose i have to write
writeRTC readRTC
0xAD Received 0x2D
0xBF 0x3F
0xCB 0x4B

but i have write
0x23 Received same 0x23
0x55 Received same 0x55

and also i have to write in SRAM address then same data received . so can you please check below i2c read and write function.

void writeRTC(uint8_t highByte, uint8_t lowByte, uint8_t data)
{
I2C1CONbits.SEN = 1; // Initiate Start condition
__delay_us(50);

// Send device address and memory address
I2C1TRN = 0b11011110 ; //(RTC_I2C_ADDRESS_WRITE << 1); //| 0b11011110; // D0 + Write
while (I2C1STATbits.TRSTAT) {}

I2C1TRN = highByte;
while (I2C1STATbits.TRSTAT) {}

I2C1TRN = lowByte;
while (I2C1STATbits.TRSTAT) {}

// Send data
I2C1TRN = data;
while (I2C1STATbits.TRSTAT) {}

// Ensure that the write operation is completed
while (I2C1STATbits.ACKSTAT) {}

I2C1CONbits.PEN = 1; // Initiate Stop condition
while (I2C1CONbits.PEN) {}

// Add a small delay to allow the EEPROM's internal write cycle to complete
__delay_ms(1); // Adjust the delay as needed
}
// Function to read data from the MCP7940N RTC
uint8_t readRTC(uint8_t highByte, uint8_t lowByte) {
I2C1CONbits.SEN = 1; // Initiate Start condition
unsigned char x;
__delay_ms(1);
//while (I2C1CONbits.SEN);// {}

I2C1TRN = 0b11011110; //(RTC_I2C_ADDRESS_READ << 1); //| 0b11011110; // D1 + Write (Device address with R/W bit set for write)
while (I2C1STATbits.TRSTAT) {}

I2C1TRN = highByte;
while (I2C1STATbits.TRSTAT) {}

I2C1TRN = lowByte;
while (I2C1STATbits.TRSTAT) {}

I2C1CONbits.RSEN = 1; // Initiate repeated Start condition
while (I2C1CONbits.RSEN){}

I2C1TRN =(0b11011111 ) ; //(RTC_I2C_ADDRESS_READ << 1) | 0b11011111; // A0 + Read (Device address with R/W bit set for read)
while (I2C1STATbits.TRSTAT) {}

I2C1CONbits.RCEN = 1; // Enable reception
__delay_us(50);
// while (!(I2C1STATbits.RBF)) {}
// int i =0;


int data = I2C1RCV; // Read received data

I2C1CONbits.ACKDT = 1; // Set ACK bit to NACK (no acknowledge) for the last byte
I2C1CONbits.ACKEN = 1; // Send NACK
while (I2C1CONbits.ACKEN) {}

I2C1CONbits.PEN = 1; // Initiate Stop condition
while (I2C1CONbits.PEN) {}


return data;
}


its changes will required please let me know . as soon as possible

 

[FvM]

I don't recognize valid MCP7940 access.
It expects one I2C address byte 0xDE (as written) and one register address byte, not yet existing in your code.

 

[KlausST]

Hi,

and for "reading" a byte you still should "transmit" an "0xFF" byte.

* "1" for "releasing the data bus SDA line (not driven by master, pulled up by resistor, pulled down by slave)
* and sending out 8+1 SCK clock cycles.

I recommend to read the I2C specification, or at least basic I2C operation documentation.

Klaus