TM4C123GXL: I2C Communication and the bno055

Hello Zero PD,

I would be adding another PDF to the read list. The TM4C129x application note for I2C, especially the section which shows what happens when specific commands are given using I2CMasterControl.

www.ti.com/.../spma073.pdf

Regards
Amit

Amit,

Thank you. I believe that document was the missing piece I couldn't wrap my head around - the description of what the master control commands are doing.

Let me ask you this. Take a quick look at the top of that picture I included last time, the section I2C Write Access. In it, it says I need to:

1. Send a Start Bit
2. Send the Slave Address
3. Get an Ack back from the Slave
4. Send the Register Address
5. Get an Ack Back from the Slave
6. Send the Data byte
7. Get an Ack back from the Slave
8. Send a Stop Bit.

So to do that, after reading the document you sent me, I should have to write a function that:

1. Loads the Slave Address
2. Loads the Register Address into the i2c master data register.
3. Calls I2C Master Control ( I2C Master CMD Burst Send Start ) to send the slave address, wait for an ack from the slave, then send the register address, get an ack back from the slave, but not send a stop bit.
4. polls the i2c master busy to wait for the send to finish
5. Loads the data byte into i2c master data register.
6. Calls I2C Master Control ( I2C Master CMD Burst Send Finish ) to send the data byte and then a stop bit.

Here is the code I wrote:

void i2c_wait(void){
	while(I2CMasterBusy(I2C0_BASE));
	if (I2CMasterErr(I2C0_BASE) == true){
		printf("Write Error. \n");
	}
}

s8 bno_write(u8 dev_address, u8 reg_address, u8 DataPacket[10], u8 data){
	I2CMasterSlaveAddrSet(I2C0_BASE, dev_address, false);
	I2CMasterDataPut(I2C0_BASE, reg_address);
	
	I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_START);
	I2CMasterDataPut(I2C0_BASE, data);
	i2c_wait();
	delay_ms(5);
	I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_FINISH);
	i2c_wait();
	return I2CMasterErr(I2C0_BASE);
}

Does my thought process appear correct to you? The only thing that confuses me is the internals of the Master Control functions. Is there blocking code that waits for an Ack back from the slave device? If it doesn't get an ack back, does it set i2c master error boolean to true and continue or abort the operation?

Hello Zero_PD,

It seems correct except that after i2c_wait gas to come after the I2CMasterControl. The first wait has to before the I2CMasterDataPut(I2C0_BASE, data).

Regards
Amit

Thanks for all your help, Amit.

If anyone else is ever trying to use the bno055 with their tiva, I spent a week banging my head against the while but finally integrated Bosch's bno055 C Library into my project. It's a very powerful library and can make your life a lot easier if you want to use adafruit's bno055 breakout board but you are not using an Arduino microcomputer. I wrote a guide to document the process and have attached the pdf. While it's written from the perspective of the TM4C123 Tiva, it should be very useful for anyone trying to integrate the library into their microcomputer project.

Good luck.

1738.Guide - How to Integrate BNO055 Library into Tiva Launchpad Project.pdf

Hello Zero_PD,

We appreciate forum contribution, though I have not reviewed the document as of now, but surely your experience into the development and it being documented is a great step for others using the same or planning to do so.

Regards
Amit

Hi Zero_PD

Could you please share the piece of code that you used for communication over UART? especially the sequence of setting the BNO055 to one of the modes.

I am trying to get the ACC data by setting it to the ACC mode, but the data I am getting are all 00!

Thank you

Murtadha - I responded on the Adafruit forum.