Forums

Hello

I also hava a problem regarding the i2c communication with the SM72442.

I have already set up a connection between my MC and the SM72442. The first Data Byte I receive from SM72442 is alwasy 7 (length of Bytes). So this seems to be ok.

But the Data Bytes from 1 to 6 are fluctuiting a lot. For example: 1.fetch: Byte1 = 171, 2.fetch: Byte1 = 255 3.fetch Byte1 = 79...and so on.

Furthermore I get high values out of register1, although i havent applied a voltage to AVIN, AIIN, AVOUT and AIOUT pins...

The 7th Databyte is alway 0. This seems logical to me because the last bits are not used and reserved.

1. question is: Is it necessary to do first the startup or something else, that values , which are send over I2C, are correct?

2. question: With the adress 0xE1I am asking for the values of register 1. Am I right?

3. Is there something i haven't mentionend so far?

Thanks for your Support!

rgds Michael

I finally got it,

 For all those whoe are struggeling with a similar issue: Take care, that the last byte must not be acknowledged ;)

Hey Michael,

I try to interface the I2c on the SM72442. The address of the slave is 0x4 (0x04??).  As you can see in the attachement, the SCL line 'walks' on a 100Khz frequency. 

on the falling edge of the 8th clockpulse and the 9th clockpulse there's is high puls on the SDA --> no ack !!!

Here some code from my project

#define I2C_MPPT_ADDR 0x4 //device address
#define I2C_READ_reg0 (0xE0)//offset base address SM72442
#define I2C_WRITE (0x00)
#define I2C_READ (0x01)

void initI2C(long baudRate)
{
long templong;
// READ_I2C = 1; //make SDL input pin
// Clk_I2C =0; //make SCL output pin

templong = ( ( ((unsigned long)GetPeripheralClock() ) / (baudRate) ) - ( ((unsigned long)GetPeripheralClock() )/10000000UL)) -1;
I2C1BRG = templong;

I2C1CONbits.DISSLW = 1; //Slew rate control disabled for Standard Speed mode (100 kHz);
I2C1CONbits.SCLREL = 1; // 1 = Releases SCLx clock
I2C1CONbits.A10M = 0; //7-bit
I2C1CONbits.I2CEN = 1; //enable I2C module

}

char read_MPPT(unsigned int addr, unsigned char *return_data)//int
{
int i;

// start
I2C1CONbits.SEN = 1; //start condition
while(I2C1CONbits.SEN);
//for(a=0;a<10;a++);
// write
I2C1TRN = I2C_MPPT_ADDR+I2C_WRITE;

i = 0;
while(I2C1STATbits.TRSTAT)
{
i++;
if(i>=100-0)//100
{
I2C1CONbits.PEN = 1;
return(0);
}
}

if(I2C1STATbits.ACKSTAT == 0) // 0 = ACK

... 

after this, there's a stop condition generated because I don't receive any ACK.

Hope you can see some strange code or something?!

THANX in advance.

Greetz,

Michiel

 Hello Michiel,

I can't say if your code is right because i dont now the Register of the used MCU and more details.

But to read out a register you have to do following precedure:

Send Start condition

Send Address with Write enable (which is in your case 00001000 = 0x08 (With WriteEnable Bit) )

Send the Register address you want to read (which is 0xE0 for Register 0)

Send Stop condition

Send a new start condition

Send Address with Read enable (which is in your case 00001001 = 0x09 (With ReadEnable Bit))

Read 8 Bytes (Length Byte + 7 Register Bytes) and acknowledge every byte but not the last one!

Send a Stop condition

So it works fine in my application. And i receive a acknowledge of the SM72442

I hope this helps you

Regards Michael