TMS320F28035: I2C SDA Line is being pulled

Shalini Addepalli

Part Number: TMS320F28035
Other Parts Discussed in Thread: C2000WARE

Hello,

I am using a TMS320F28035 Microcontroller's I2C as a master. There are 2 Slave devices connected 1. EEPROM (M24M02-DR) and 2. Accelerometer (LSM9DS1). There is no issue with the I2C communication when there is only EEPROM as a slave. When I also connect the Accelerometer, the SDA line is being pulled low.

To solve the above problem, I want to send clock pulses on the SCL line, configuring the SCL line as GPIO. The accelerometer datasheet says the Clock high time = 0.6 usec and Clock low time = 1.3 usec in the fast mode (400KHz). To generate the clock, I am setting and clearing the GPIO pin with delays in between. The delay is generated by DELAY_US(); function. But this does not seem to generate the clock in the way I expected. I see a much lower frequency.

Can you please help me with where I am doing wrong? And the slave (Accelerometer) does not release the SDA line even after doing so...

Thanks,

Shalini Addepalli

over 6 years ago

0 MEGHANA MANAVAZHI over 6 years ago

TI__Genius 10215 points

hi Shalini ,

Are you using the below program as reference

C2000Ware\device_support\f2803x\examples\c28\i2c_eeprom

Please check the setting done for the below code instructions:

I2caRegs.I2CPSC.all = 6; // Prescaler - need 7-12 Mhz on module clk
I2caRegs.I2CCLKL = 10; // NOTE: must be non zero
I2caRegs.I2CCLKH = 5; // NOTE: must be non zero

Regards.

0 Shalini Addepalli over 6 years ago in reply to MEGHANA MANAVAZHI

Prodigy 90 points

Hello Meghana,

I am able to do I2C in normal conditions, well. What happened suddenly is, the LSM9DS1 (accelerometer - slave) started pulling the SDA line low. Because of this, TMS320F28035 does not produce even the clock signals on the I2C SCL line.

When I read many TI forums, it tells that the work around with slave pulling a SDA line low problem is to configure the SCL and SDA lines as GPIO and send out clock pulses on SCL line. When I use the SCL line as GPIO, I am not able to generate a clock with particular values of 100KHz frequency (4 usec HIGH time and 4.7 usec LOW Time ) as per the LSM9DS1 datasheet.

Thanks,

Shalini Addepalli

0 MEGHANA MANAVAZHI over 6 years ago in reply to Shalini Addepalli

TI__Genius 10215 points

hi Shalini,

Were you able to make any progress on this ?

Does this behavior remain even with any other slave devices ?

Regards.

0 Shalini Addepalli over 6 years ago in reply to MEGHANA MANAVAZHI

Prodigy 90 points

Hi Meghana,

Yes, there was no problem with the software. The particular slave which was pulling SDA line low, was because I was using a 750 mm length cable. When I switched to a smaller cable length, it started responding.
Thanks,
Shalini Addepalli

0 MEGHANA MANAVAZHI over 6 years ago in reply to Shalini Addepalli

TI__Genius 10215 points

Good you hear that you were able to proceed.

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TMS320F28035: I2C SDA Line is being pulled