Epic/MSP430 - I2C Issue after using SPI about tinyos-main HOT 5 CLOSED

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

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.

Patch applied as temp. fix in rev 5508. I still can not recreate the problem on 
my hw though.

Vlado

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.