I2C repeated start with TC387

[ntimm]

Hi,

i'm trying to communiacte with a PMBus device via I2C. For that I need to generate a repeated Start between the address write and consecutive read. I'm using a TC387 with ILLD 1.14 and the following code:

IfxI2c_I2c_Config config;
	IfxI2c_I2c_initConfig(&config, &MODULE_I2C0);

	const IfxI2c_Pins pins = { &IfxI2c0_SCL_P15_4_INOUT,
				   &IfxI2c0_SDA_P15_5_INOUT,
				   IfxPort_PadDriver_cmosAutomotiveSpeed1 };

	config.pins = &pins;
	config.baudrate = 400000;
	IfxI2c_I2c_initModule(&t->i2c, &config);
	IfxI2c_I2c_deviceConfig i2cDeviceConfig;
	IfxI2c_I2c_initDeviceConfig(
		&i2cDeviceConfig,
		&t->i2c); /* Device config for Bus of i2c handle */

	i2cDeviceConfig.deviceAddress = addr;
	i2cDeviceConfig.enableRepeatedStart=TRUE;
	IfxI2c_I2c_initDevice(&t->i2cDev, &i2cDeviceConfig);

if (IfxI2c_I2c_write(&t->i2cDev, data, 1) != IfxI2c_I2c_Status_ok) {		
		return FALSE;
	}
if (IfxI2c_I2c_read(&t->i2cDev, data, 1) != IfxI2c_I2c_Status_ok) {
		return FALSE;
	}

For non-PMBus devices this code works fine with enableRepeatedStart set to FALSE. When its set to TRUE the the program doesn't return from IfxI2c_I2c_write. It hangs in an endless loop at 

 if (!i2cDevice->enableRepeatedStart)
    {
        IfxI2c_releaseBus(i2c);
    }
    else
    {
        //wait until bus is free
        while (IfxI2c_getProtocolInterruptSourceStatus(i2c, IfxI2c_ProtocolInterruptSource_transmissionEnd) == FALSE)
        {}

        IfxI2c_clearProtocolInterruptSource(i2c, IfxI2c_ProtocolInterruptSource_transmissionEnd);
    }

waiting for the transmission end interrupt.

After the write the SDA line stays high while SCL stays low

Any ideas?

Kind regards

[Nambi]

Hi,

Can you try initiating the subsequent write after the repeated start condition?

Best Regards.

[ntimm]

Hi,

IfxI2c_I2c_write doesn't return from the first write. It waits forever for the Transmission End Signal at

//wait until bus is free
        while (IfxI2c_getProtocolInterruptSourceStatus(i2c, IfxI2c_ProtocolInterruptSource_transmissionEnd) == FALSE)
        {}

When I forcefully skip this with the help of a debugger, I get a "Bus busy" error at the next write.

Kind regards

[Mayur_Gaikwad]

Hi, 

I am also facing same problem for TC397. 

Please let me know if you got any solution. 

Thanks

[MoD]

The problem here is the code:

    if (!i2cDevice->enableRepeatedStart)
    {
        IfxI2c_releaseBus(i2c);
    }
    else
    {
        //wait until bus is free
        while (IfxI2c_getProtocolInterruptSourceStatus(i2c, IfxI2c_ProtocolInterruptSource_transmissionEnd) == FALSE)
        {}

        IfxI2c_clearProtocolInterruptSource(i2c, IfxI2c_ProtocolInterruptSource_transmissionEnd);
    }

I don't know why the sw should wait here for TX_END. From my point of view it is wrong because the the TX_END flag is reset shortly before and there is no trigger which result in a new TX_END. 

Change the code to:

    if (!i2cDevice->enableRepeatedStart)
    {
        IfxI2c_releaseBus(i2c);
    }
    else
    {
    }

and test again.

[ntimm]

Hi,

unfortunately this doesn't fix the issue for me.

When I delete the 2 lines the subsequent call of IfxI2c_I2c_read fails with a "bus busy" error and he CLK line is held low.

// bus free?
    if (IfxI2c_busIsFree(i2c) == FALSE)
    {
        status                    = IfxI2c_I2c_Status_busNotFree;
        i2cDevice->i2c->busStatus = IfxI2c_getBusStatus(i2c);
        i2cDevice->i2c->status    = status;
        return status;
    }

This code returns with i2cDevice->i2c->busStatus == IfxI2c_BusStatus_busyMaster.

Anything I might need to do between the write and read?

Kind regards

[MoD]

The problem is that the code is not really prepared to be use with repeated start as you can see where you hang. When you are in repeated start then the status of read and write must be IfxI2c_BusStatus_busyMaster but the function ask for bus free which is only correct when there is no repeated start. You should change the read/write function also that when it is in repeated start then the state should be free (for first call) or IfxI2c_BusStatus_busyMaster in subsequent calls.

[Anand2603]

Hi

  I am also working on the SMBus, if you know how to make the Bus Ideal from software side during  very first Read Call ? Because as mentioned in User Manual the
clock SCL stays low as long as no further communication is requested after Repeated Start, so to bring the Bus Ideal, the SCL should be set to High as per my understanding. So is there any way from software side to bring the  SCL in to HIGH state to bring BUS in IDEAL state.

[VG]

Hi,

Attached patch helps me.

Usage:
/* Write data to device */
IfxI2c_I2c_restart(&g_i2cDev);
while(IfxI2c_I2c_write(&g_i2cDev, &rxBuffer[0], 3) == IfxI2c_I2c_Status_nak);
/* Read the reg address */
while(IfxI2c_I2c_read(&g_i2c, &data[0], 2) == IfxI2c_I2c_Status_nak);