16 bit data write using I2C interface in OMAPL138

Shino Samuel

Other Parts Discussed in Thread: INA219, LM75A, OMAP-L138

I am facing some problems; while trying to write a 16bit config register data to INA219 V&I Monitor using I2c. so i need some clarification on whether 16bit write is possible (Reg. Pointer + databyte 1 + databyte 2) . If this pattern is wrong , try to help me by providing the steps to do so. i didn't find any difficulty in 16bit read from INA219 registers.

Along with that i need clarification on whether there is a need of sending the (slave address + R/W) data apart from writing data to the SAR Reg and Tx/Rx bit in ICMDR Register.

Hoping for some helping hands from someone

Thanks

----------------------------

uint32 uint32_INA219RegisterWrite ( uint16 in_addr, uint8 in_reg_addr, uint8 in_databyte1, uint8 in_databyte2)

{

uint32 rtn;

uint8 uint8_I2Cdata[3];

//array for storing register pointer & 2xbyte of data

uint8_I2Cdata[0] = in_reg_addr;

uint8_I2Cdata[1] = in_databyte1;

uint8_I2Cdata[2] = in_databyte2;

// write the register

rtn = uint32_I2CWrite(I2C0, in_addr, uint8_I2Cdata, WRITE_LENGTH, SET_STOP_BIT_AFTER_WRITE);

return (rtn);

}

uint32 uint32_INA219RegisterRead(uint16 in_addr, uint8 in_reg_addr, uint8 *dest_buffer)

{

uint32 rtn;

// write the register address that we want to read.

rtn = uint32_I2CWrite(I2C0, in_addr, &in_reg_addr, ADDRESS_LENGTH, SKIP_STOP_BIT_AFTER_WRITE);

if (rtn != ERR_NO_ERROR)

return (rtn);

// clock out the ina219 register data.

rtn = uint32_I2CRead(I2C0, in_addr , dest_buffer, READ_LENGTH , SKIP_BUSY_BIT_CHECK);

return (rtn);

}

over 13 years ago

0 Norman Wong over 13 years ago

Guru 26430 points

The datasheet for INA219 indicates that it does use a repeated start for read operations. I am not familiar with your I2C libary. I am guessing the code should look something like this:

uint32 uint32_INA219RegisterWrite ( uint16 in_addr, uint8 in_reg_addr, uint16 in_data)
{
uint32 rtn;
uint8 uint8_I2Cdata[3];

//array for storing register pointer & 2xbyte of data
uint8_I2Cdata[0] = in_reg_addr;
uint8_I2Cdata[1] = (uint8)(in_data >> 8); // MSB
uint8_I2Cdata[2] = (uint8)in_data;        // LSB

// write the register
rtn = uint32_I2CWrite(I2C0, in_addr, uint8_I2Cdata, 3, SET_STOP_BIT_AFTER_WRITE);
return (rtn);
}

uint32 uint32_INA219RegisterRead(uint16 in_addr, uint8 in_reg_addr, uint16 *out_data)
{
uint32 rtn;
uint8 uint8_I2Cdata[2];
uint16 temp;

// write the register address that we want to read.
rtn = uint32_I2CWrite(I2C0, in_addr, &in_reg_addr, 1, SET_STOP_BIT_AFTER_WRITE);
if (rtn != ERR_NO_ERROR) return (rtn);

// clock out the ina219 register data.
rtn = uint32_I2CRead(I2C0, in_addr , uint8_I2Cdata, 2 , SET_STOP_BIT_AFTER_READ);
if (rtn != ERR_NO_ERROR) return (rtn);

temp   = uint8_I2Cdata[0]; // MSB
temp <<= 8;                // Shift into upper spot.
temp |= uint8_I2Cdata[1]; // LSB

*out_data = temp;

return (rtn);
}

0 Shino Samuel over 13 years ago in reply to Norman Wong

Intellectual 970 points

thank u for the response

0 Shino Samuel over 13 years ago in reply to Shino Samuel

Intellectual 970 points

i just want someone's view on the issue with I2C. i am working with 9 I2C slaves (6 INA219, 2 LM75A and PMIC) . in testing all the 6 INA219 IC's works perfectly but the 2x LM75 IC,s are not responding it will pull the busy bit to HIGH . i used the same code for INA219 read/write; the only difference is the I2C address . we also used a I2C level shifter in the Bus (1.8V -> 3.3V) for the INA219 but the logic level have no conflicts with LM75. Is ther any suggessions other than the issues like bus levels , logic levels slave address error .

0 1258021 over 13 years ago in reply to Shino Samuel

Genius 5120 points

Is OMAP-L138 operating at 1.8V or 3.3V?

What are the voltage levels for OMAP-L138, INA219 and LM75?

Sorry, I don't have noticed anything else

Regards,

GSR

0 Abhijit Das84416 over 13 years ago in reply to 1258021

TI__Intellectual 880 points

Hello ESR,

The CPU of the OMAP L138 1.2 V / 1.3 V but GPIO is configurable for 1.8V or 3.3 V. But I2C bus of OMAP L138is 1.8 V signal only. Voltage level of INA219 : 3.0 to 5.5V & LM75 Operating voltage level is approx 2.7 V to 5.5 Volt. Level Shifter is recommended for both device. Please confirm LM75 or LM75A.

-- Abhijit

0 Shino Samuel over 13 years ago in reply to 1258021

Intellectual 970 points

Hi all

OMAP L138 is working at 1.8V

INA219 - 3.3V

LM75AIM - 3.3V

for more information , NACK bit in the ICSTR Reg is TRUE after the ICMDR Reg Configuration. I analyse it as a missing of ACK after sending address so is it advisable to look on clock skew or any other delay problems specifically with hardware ?

0 Norman Wong over 13 years ago in reply to Shino Samuel

Guru 26430 points

Some usual questions. What is the SCL frequency? The LM is a slower device than the INA. What is the value of the pullup resistors on SCL and SDA? The OMAP-L138 might have internal pullups.

0 Shino Samuel over 13 years ago in reply to Norman Wong

Intellectual 970 points

thanks for your replies .

We diagnose it as a problem with delay and track . With the help of I2C analyzer we found out the cause. So we worked with hardware and now the LM75 AIM IC is acknowledging correctly .

I prefer I2C analyzer as best way to find out issues with I2C communication

0 Scott Battocchi over 13 years ago in reply to Abhijit Das84416

Prodigy 210 points

Abhijit,

I was not able to find any information in the OMAP L138 datasheet about the I2C voltage being only 1.8V capable. It looks like it is in the DVDD3318_A power group which is configured for 3.3V in our application.

Thanks for clarifying,

Scott Battocchi

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16 bit data write using I2C interface in OMAPL138