TI TivaC Launchpad I2C Errors - i2c

Question

I am trying to communicate over I2C with a Pololu MinIMU9v2 from a TM4C123GXL Launchpad, but every time I try to write to the bus, I am getting I2C_MASTER_ERR_ADDR_ACK and I2C_MASTER_ERR_DATA_ACK. Printing out the slave address shows that it looks right, so I'm thinking this may be something I may be doing wrong with the use of the TI Launchpad driver library.
Here's the initialization routine:
void
InitI2CBus(void)
{
// Initialize the TM4C I2C hardware for I2C0
SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
SYSCTL_XTAL_16MHZ);
SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
GPIOPinConfigure(GPIO_PB2_I2C0SCL);
GPIOPinConfigure(GPIO_PB3_I2C0SDA);
GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_3);
// Initialize the bus
I2CMasterInitExpClk(I2C0_BASE, SysCtlClockGet(), false);
}
Here is the code that attempts to read a byte from the device:
uint8_t
ReadByte(uint8_t slaveAddr, uint8_t subAddr)
{
// Write SUB
slaveAddr |= 1; // Set LSB to writemode
I2CMasterSlaveAddrSet(I2C0_BASE, slaveAddr, false);
I2CMasterDataPut(I2C0_BASE, subAddr);
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_SEND);
while(I2CMasterBusy(I2C0_BASE)) { }
if (CheckError())
{
return 0;
}
// Read data
slaveAddr &= ~1; // Set LSB to readmode
I2CMasterSlaveAddrSet(I2C0_BASE, slaveAddr, true);
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);
while(I2CMasterBusy(I2C0_BASE)) { }
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);
while(I2CMasterBusy(I2C0_BASE)) { }
uint8_t response = I2CMasterDataGet(I2C0_BASE);
if (CheckError())
{
return 0;
}
return response;
}
Any ideas what I may be doing wrong?

Answer 1

I was having a heck of a time getting my I2C bus working on this board. I'm not sure if this is your issue, but here's the initialization code I'm using (I'm on I2C2):
1. SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C2);
2. SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
**3. GPIOPinTypeI2CSCL(GPIO_PORTF_BASE, GPIO_PIN_6);**
4. GPIOPinTypeI2C(GPIO_PORTF_BASE, GPIO_PIN_7);
5. GPIOPinConfigure(GPIO_PF6_I2C2SCL);
6. GPIOPinConfigure(GPIO_PF7_I2C2SDA);
7. I2CMasterInitExpClk(I2C2_BASE, SysCtlClockGet(), false);
8. I2CMasterSlaveAddrSet(I2C2_BASE, 0x48, false);
Line 3 was missing from most of the examples I could find, and I noticed it's also missing from your code. Before I added this line, I couldn't get my I2C bus to do anything; after adding it it's at least transferring data.
I'm not sure if this is the source of your issue or not, but thought I'd pass it along in case it helps.