Problem with SensorLib I2c functions

dinu mihailescu

Hello,

Im trying to connect the MPU6050 (adress 0x68) to the Tiva C Launchpad however I cant even read the WHO_AM_I register (0x75). Instead of the desired value 0x68 I get zero as result.Can someone please tell me which part of my code is wrong? Thank you a lot!

bool done;
tI2CMInstance sI2CInst;

void callback(void *pvData, uint_fast8_t ui8Status)
{
	if(ui8Status!=I2CM_STATUS_SUCCESS)
	{
		//FEHLER
	}
	else
		done=true;
}

void I2C1IntHandler(void)
{
	//UARTprintf("I2C IRQ\n");
	I2CMIntHandler(&sI2CInst);

}

void tiva_i2c_init(uint32_t ui32Base, uint_fast8_t ui8Int, uint32_t ui32Clock)
{
	I2CMInit(&sI2CInst, ui32Base, ui8Int, 0xff, 0xff,ui32Clock);
}

int tiva_i2c_read(unsigned char slave_addr,unsigned char reg_addr,unsigned char length, uint8_t *data)
{
	done=false;

	uint_fast8_t result=I2CMRead(&sI2CInst, slave_addr,reg_addr,1,data,length,callback,0);
	while(!done)
	{
	}
	if(result==1)
		return 0;
	else
		return 1;
}


int main (void)

{
        SysCtlClockSet(SYSCTL_SYSDIV_3 | SYSCTL_USE_PLL | SYSCTL_XTAL_16MHZ | SYSCTL_OSC_MAIN);
        ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
	ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C1);
	ROM_GPIOPinConfigure(GPIO_PA6_I2C1SCL);
	ROM_GPIOPinConfigure(GPIO_PA7_I2C1SDA);
	ROM_GPIOPinTypeI2CSCL(GPIO_PORTA_BASE, GPIO_PIN_6);
	ROM_GPIOPinTypeI2C(GPIO_PORTA_BASE, GPIO_PIN_7);
        tiva_i2c_init(I2C1_BASE, INT_I2C1, ROM_SysCtlClockGet());

	unsigned char test=2;

	tiva_i2c_read(0x68,0x75,1, &test);
	if(test==0x68)
		UARTprintf("Connected...\n");
	else
	{
		UARTprintf("ERROR\n");
		UARTprintf("WHO_AM_I: %i\n",test); //Result is always ZERO
		UARTprintf("***STOP***");
		while(1){}
	}

while(1){}

}

over 11 years ago

0 Luis Afonso over 11 years ago

Guru 20670 points

Hi dinu,

What launchpad are you using? There are 2 Tiva launchpads now.

Did you use pull-ups? if memory serves, the data doesn't have internal pull-ups and the clk also doesn't

0 dinu mihailescu over 11 years ago in reply to Luis Afonso

Prodigy 40 points

Hi Luis,

I'm using the TM4C123GXL launchpad. No I haven't added pull-ups.

I thought they would be activated automatically on the launchpad when the I2C block is activated but maybe I misunderstood something...

0 Luis Afonso over 11 years ago in reply to dinu mihailescu

Guru 20670 points

I already had this problem before. You should be able to set up manually internal pull-ups using the GPIO API. With

GPIOPadConfigSet(GPIO_PORTF_BASE,GPIO_PIN_4,GPIO_STRENGTH_2MA,GPIO_PIN_TYPE_STD_WPU);

Just change to your pins. Remember to never put the SCL in open drain. Try this before you configure the pins as SCL and DATA.
Before:

ROM_GPIOPinConfigure(GPIO_PA6_I2C1SCL);

ROM_GPIOPinConfigure(GPIO_PA7_I2C1SDA);

ROM_GPIOPinTypeI2CSCL(GPIO_PORTA_BASE, GPIO_PIN_6);

ROM_GPIOPinTypeI2C(GPIO_PORTA_BASE, GPIO_PIN_7);

Look into 16.3 in the datasheet. There says you need external pull-ups.

0 dinu mihailescu over 11 years ago in reply to Luis Afonso

Prodigy 40 points

Ok I tried it with the config code

GPIOPadConfigSet(GPIO_PORTA_BASE,GPIO_PIN_6,GPIO_STRENGTH_2MA,GPIO_PIN_TYPE_STD_WPU);
GPIOPadConfigSet(GPIO_PORTA_BASE,GPIO_PIN_7,GPIO_STRENGTH_2MA,GPIO_PIN_TYPE_STD_WPU);
ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C1);
ROM_GPIOPinConfigure(GPIO_PA6_I2C1SCL);
ROM_GPIOPinConfigure(GPIO_PA7_I2C1SDA);
ROM_GPIOPinTypeI2CSCL(GPIO_PORTA_BASE, GPIO_PIN_6);
ROM_GPIOPinTypeI2C(GPIO_PORTA_BASE, GPIO_PIN_7);

but I still get the wrong results when reading from the device.

0 Luis Afonso over 11 years ago in reply to dinu mihailescu

Guru 20670 points

I said to try because i didn't remember if it worked before. Without sending anything are the pins at 3.3V? It would be easier to check with a logic analyzer.

You probably really have to add the external pull-ups

0 dinu mihailescu over 11 years ago in reply to Luis Afonso

Prodigy 40 points

I have added two pull-ups but the result is still the same.

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Problem with SensorLib I2c functions