Tiva TM4C12294 I2C High Speed

RAJA BALAJI KARTHIKEYAN

Hi,

i am trying to get the I2C peripheral working at 3.3M High speed mode. I have read the datasheet (18.4.2 Configure the I2C Master to High Speed Mode).

I am following the below sequence

1. HWREG(I2C2_BASE + I2C_O_MTPR) = TPR value for 3.3M;

2. HWREG(I2C2_BASE + I2C_O_MCS) = 0x50;

3. HWREG(I2C2_BASE + I2C_O_MSA) = 0x08;

4. delay for transition to complete.

5. Then, start a data transfer to slave device.

But the frequency is set around 6.5MHz. It is not changing even if a different value is written to TPR value. (The value in TPR register is in effect and setting the correct frequency if in standard mode)

Any idea of how to fix this issue. what am i missing in the configuration ?

Thanks in advance !!

over 9 years ago

0 RAJA BALAJI KARTHIKEYAN over 9 years ago

Prodigy 70 points

I had missed to set HS bit in I2C_MTPR. With this addition, i am able to get 3.3MHz. But i have only idea of why i was getting 6.6MHz earlier. :)

0 Amit Ashara over 9 years ago

TI__Guru**** 244400 points

Hello Raja

What is the system frequency being used?

Also there is no mention of any code that can be used to replicate the 6.5MHz I2C SCL

Regards
Amit

0 RAJA BALAJI KARTHIKEYAN over 9 years ago in reply to Amit Ashara

Prodigy 70 points

Hi Amit,

System frequency is 80 MHz. The TPR counter value i wrote was to set it at 3.33M. But i have missed to enable HS bit in the same register. I guess, this has caused some misbehavior and the I2C clock has set at 6.5MHz.

Regards,

Raja

0 Amit Ashara over 9 years ago in reply to RAJA BALAJI KARTHIKEYAN

TI__Guru**** 244400 points

Hello Raja,

By the equation it should have resulted in 1MHz.

Regards
Amit

0 RAJA BALAJI KARTHIKEYAN over 9 years ago in reply to Amit Ashara

Prodigy 70 points

Hi Amit,

If I dont set the HS bit and do not sent the special command for HS - 1MHz is set

If I dont set the HS bit , but sent the special command for HS - 6.5 MHz is set

If I set the HS bit and also sent the special command for HS - 3.33 MHz is set

This is the observation i have made.

Regards,

Raja

0 Amit Ashara over 9 years ago in reply to RAJA BALAJI KARTHIKEYAN

TI__Guru**** 244400 points

Hello Raja,

Thanks for the clarification. That does make sense as the TIMER_PRD is 0 and by equation the SCL Period in HS would 1/12 of the System Clock

SCL_PERIOD = 2 × (1 + TIMER_PRD) × (SCL_LP + SCL_HP) × CLK_PRD

TIMER_PRD default is 1, SCL_LP is 2 and SCL_HP is 1.

SCL_PERIOD = 2 × (1 + 1) × (2 + 1) × CLK_PRD
SCL_PERIOD = 2 × (2) × (3) × CLK_PRD
SCL_PERIOD = 12 × CLK_PRD

Regards
Amit

0 RAJA BALAJI KARTHIKEYAN over 9 years ago in reply to Amit Ashara

Prodigy 70 points

Hi Amit,

As per your formula, SCL_HP and SCL_LP are 2 and 1, only if HS bit is set. (which I missed to set)

and also, I had written the TPR value. So, it is not the default value of 1.

Thanks,

Raja

0 Amit Ashara over 9 years ago in reply to RAJA BALAJI KARTHIKEYAN

TI__Guru**** 244400 points

Hello Raja,

Even though the application did not set the HS bit when writing the HS Counter value, when you instructed it to do a HS transfer it took the default value of HS mode as 1.

Regards
Amit

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Tiva TM4C12294 I2C High Speed