I2C loopback mode

ketankumar patel

Prodigy 50 points

I want to perform I2C loopback test in my standalone application.But I dont know its flow for performing it.

Do I have followed polling FIFO method.But I am not getting loopback performed.

My code flow:

->disable the I2C module

->configure I2C_SYSTEST register for loopback mode

->add thresold value in Rx FIFO & tx FIFO

->enable the module (set I2C_EN bit )

-> XRDY bit of I2C_STAT register...if 1 then write to I2C_DATA register for txthresold+1 times

->poll RRDY bit of I2C_STAT register...If 1 read the I2C_data register...

Please let me know if I forget anything to be done in my code.

over 13 years ago

0 Rodrigo Castaneda over 13 years ago

TI__Intellectual 785 points

Hi Ketankumar Patel,

Seems to me like you are doing all right, but if you really were doing everything correctly you were working, what crosses my mind is to watch for

I2Ci.I2C_STAT[12] BB bit = 0

You should not start your sequence if it is set, and wait until is cleared. But I admit this is an obvious you probably doing this right now. other thing that I can think of is check for FREE bite,

I2Ci.I2C_SYSTEST[14] FREE = 1

When is cleared, If Master mode, it stops after completion of the ongoing bit transfer. In slave mode, it stops during the phase transfer when 1 byte is completely transmitted/received.

When set, free running mode.

Regards,

Rodrigo

0 ketankumar patel over 13 years ago in reply to Rodrigo Castaneda

Prodigy 50 points

It is still not working.Please let me know steps to perform loopback mode of I2C.

Below is my code:

===============================

//intialize i2c controller

i2c_init(0x40,100000); //(address, speed)

//disabling module & putting it into F/S mode=default mode
writew(I2C_CON_EN,&i2c_base->con);

// free running mode + loopback test mode +enabling system test mode
writew(0xF000,&i2c_base->systest);

//enabling module
writew(I2C_CON_EN,&i2c_base->con);

//waiting for bus to free

while(I2C_STAT_BB & readw(&i2c_base->stat));

//transmit

while(!(readw(&i2c_base->stat) & I2C_STAT_XRDY));
printf("\nTransmit ready\n");
writew(0x55,&i2c_base->data); //writing only one byte as TXTHRS=0 default

///receive
while(!(readw(&i2c_base->stat) & I2C_STAT_RRDY));
printf("\nReceiver ready\n");
data_rx=readw(&i2c_base->data); //read data register
printf("\nReceived data=%d\n",data_rx);

=================================================

I can poll both RRDY & XRDY but received data is always 0.& thats the problem.Let me know if I doing wrong or missing.

0 Rodrigo Castaneda over 13 years ago in reply to ketankumar patel

TI__Intellectual 785 points

Hi Ketankumar:

you may want to take a look at the link bellow, it have some interesting tool you may find usefull

http://elinux.org/Board_Bringup_Utilities

Regards,

Rodrigo

0 Rodrigo Castaneda over 13 years ago in reply to Rodrigo Castaneda

TI__Intellectual 785 points

Hi Ketankumar:

I insist on you are missing, the prescaler and SCL con figurations,

//disabling module & putting it into F/S mode=default mode
writew(I2C_CON_EN,&i2c_base->con);

// free running mode + loopback test mode +enabling system test mode
writew(0xF000,&i2c_base->systest);

// prescaler settings (I2Ci.I2C_PSC)
writew(0x????,&i2c_base->psc);

// Low and hight time values (I2Ci.I2C_SCLL and I2Ci.I2C_SCLH)
writew(0x????,&i2c_base->scll);
writew(0x????,&i2c_base->sclh);

// setup required fifo size - 1. RTRSH and XTRSH (I2Ci.I2C_BUF)
writew(0x????,&i2c_base->buff);

//enabling module
writew(I2C_CON_EN,&i2c_base->con);

Regards,

Rodrigo

0 ketankumar patel over 13 years ago in reply to Rodrigo Castaneda

Prodigy 50 points

Hi,

Its working now.Thanks Rodrigo.

thanks,

Ketan Patel

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I2C loopback mode