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I am attempting to connect my Launchpad device to the Pololu MinIMU9v2 9DoF sensor via the I2C bus. I am working in a Linux environment, compiling with arm-none-eabi-gcc, and I have downloaded the sw-ek-tm4c123gxl zip file from the Texas Instruments website.

In digging through the drivers download, I identified a folder (examples/peripherals/i2c) that contains 3 demonstrations (each in a single C file) for using the I2C bus. One runs the Launchpad as a slave, the next configures it as a loopback, and finally, there is one that interfaces the Launchpad with an Atmel I2C-based memory device using what it refers to as "soft I2c".

I'm assuming that the "soft" part of this means that it's software based, utilizing interrupts and all. I'm looking for a simpler solution, preferably without interrupts. The loopback example worked like a charm, for instance, but in modifying it, I can't seem to get it to communicate with the MinIMU9, no matter what I try. The documentation for the MinIMU9 is pretty clear, but I think I'm just lacking an understanding on how to use this driver software.

Finally, I don't want to reinvent the wheel, but I can't seem to find any one else talking about I2C and the stellaris or tivac launchpads. Am I way off the mark in trying to implement this in this way? If not, is there an easier way to go about this? And, if not, where can I learn more about whatever it is that I'm missing?

artless noise
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Bobby
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  • It might be worth mentioning that I would eventually like to run this as a task under FreeRTOS. – Bobby Mar 05 '14 at 04:20
  • It sounds like you are on the right track. You should be using either I2C or SPI to communicate with that sensor. And getting the Tivaware I2C examples to run is a great place to start. To get more specific help you need to provide more specific details. How did you connect the sensor? What slave address did you choose? What is your code? What fails to work? – kkrambo Mar 05 '14 at 14:20
  • You were very right. I will post an answer with specifics. – Bobby Mar 07 '14 at 04:13
  • possible duplicate of [TI TivaC Launchpad I2C Errors](http://stackoverflow.com/questions/22312136/ti-tivac-launchpad-i2c-errors) – artless noise Mar 14 '14 at 17:23

1 Answers1

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I was able to figure it out after all. One thing that I hadn't noticed in the first place is that Texas Instruments provides a PDF peripherals resource that discusses the usage of their driver library. Unfortunately, this documentation is far from comprehensive, and probably would have still required someone to bury themselves in the code were it not for the examples.

Now, the peripheral examples required a bit of work to get going. To save some time and effort, I tried copying master_slave_loopback.c over the top of examples/project/project.c, modified it according to the comments within the file, and then I was able to compile the example and run it with immediate success.

Next, I attempted to convert the new project.c file into something that would allow me to communicate with the MiniIMU9v2. Everything seemed straight forward for the most part. I commented out anything that looked like it was related to loopback functionality, but when I would try to execute the program, it would hang on the following line:

while(I2CMasterBusy(I2C0_BASE)) { }

Overwhelmed with what I might have to do to begin troubleshooting this, I decided to post this question. Fortunately, the problem was a lot simpler and surprising to solve than I had suspected. A quick search revealed this page: http://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/316580.aspx

I changed:

GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_2 | GPIO_PIN_3);

To:

GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_3);

And this solved my problem.

Bobby
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