Epic/MSP430 - I2C Issue after using SPI about tinyos-main HOT 4 CLOSED

From vlado.handziski on February 16, 2011 14:18:11
Hi,

Can you provide a bit more info on the platform that you are using, i.e. which epoc core design and what devices are attached to the port? Switching between SPI and I2C has always been very tricky on the 1611, and the errata is full with I2C issues.

If the I2CEN was not disabled, your proposed change would effectively send a START condition. Did you check if the I2CSTT is indeed the culprit? I.e. did all successful modifications of I2CTCTL include a set I2CSTT? I wonder if this is again some timing issue or the internal I2C state machine somehow gets confused by the previous SPI signaling...

Vlado

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From [email protected] on February 17, 2011 23:48:56
No problem. The Epic core version I'm using is the 11-28-2007 version that has the flash and radio on the same bus. The only I2C device on the I2C bus is my light sensor, a Rohm BH1721FVC. I'm using a new board that I created, and I have attached the schematic.

I know that setting I2CTCTL to the particular value 0x01 isn't required, and that that value wasn't chosen because of the I2CSTT bit. I believe writing 0x00 will work. I tried some variations to determine if the value mattered, and I think I found some that didn't work (closer to 0xFF), but I didn't try too hard. After looking at the errata sheet it does seem that just writing I2CTCTL resets the I2C state machine which takes care of the problem, but I don't know for sure.

Brad

PS. The origin of writing 0x01 is because the U0TCTL register is reset to 0x01, and I found the U0TCTL register as the problem before I realized it was the same as I2CTCTL.

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From vlado.handziski on March 12, 2011 00:40:06
Patch applied as temp. fix in rev 5508. I still can not recreate the problem on my hw though.

Vlado

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From [email protected] on August 12, 2011 08:07:16
Since I had this issue I've made more of the hemera boards and some have this problem and some don't. I have no idea why.

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