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ECitt.648
ECitt.648
Associate
October 28, 2019
Question

Cannot read I2C on F303K8T6 when TIM3 is in PWM generation on all its 4 channels

  • October 28, 2019
  • 3 replies
  • 1023 views

after generating the code with cubeMX in order to have 490Hz output PWM for all TIM3 4 channels inside the main if I call (using HAL)

Hal_Tim_Base_Start(&htim3);

Hal_Tim_Pwm_start(&htim3, TIM_CHANNEL_1);

Hal_Tim_Pwm_start(&htim3, TIM_CHANNEL_2);

Hal_Tim_Pwm_start(&htim3, TIM_CHANNEL_3);

Hal_Tim_Pwm_start(&htim3, TIM_CHANNEL_4);

i2c not works correctly and I cannot read the mpu6050.

I2C is configured in fastMode (400KHz).

If I comment the 4 pwm_start line above I can read correctly the sensor when TIM3 is active and PWM is not enabled.

if I change TIM3 with TIM1 I can read correctly the mpu6050 and I can generate the PWM.

So the question is: why i2c not work when I use TIM3 and works correct when I use TIM1 ?

thanks

This topic has been closed for replies.

3 replies

berendi
berendi
Principal
October 28, 2019

What are the GPIOB->MODER and GPIOB->AFRL values values for pin 7, in the working and non-working cases?

ECitt.648
ECitt.648Author
Associate
October 28, 2019

working config

GPIOB->MODER = 00000000000000001010010101000000

GPIOB->AFR   = 01001000000000000000010000100000

not working config

GPIOB->MODER = 00000000000000001010010101001010 

GPIOB->AFR   = 01001000000000000000010000100000

berendi
berendi
Principal
October 29, 2019

Separated the bitfields for readability,

working config
 B7 B6 B5 B4 B3 B2 B1 B0
GPIOB->MODER = 0000000000000000 10 10 01 01 01 00 00 00
 
 PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0
GPIOB->AFR = 0100 1000 0000 0000 0000 0100 0010 0000
 
not working config
 B7 B6 B5 B4 B3 B2 B1 B0
GPIOB->MODER = 0000000000000000 10 10 01 01 01 00 10 10
 
 PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0
GPIOB->AFR = 0100 1000 0000 0000 0000 0100 0010 0000

Looking at the port configuration bits for PB7 (SDA) and PB6 (SCL), MODER bits are 10 for both, they are in alternate function mode, good.

Alternate function number for PB7 is 4, this is the AF number for I2C1, good.

Alternate function number for PB6 is 8, this is wrong.

See Table 14. Alternate functions in the datasheet. AF8 is not defined for PB6, so anything might happen there, it might even accidentally work.

Find out what code puts 8 in bits 24-27 of AFR[0], and correct it. The AF value for PB0 (AF0) is undefined too, and there is no reason to set PB2 to AF8 when it's not configured to alternate function mode, something is writing junk all over the place. I'd suggest going over all GPIO registers, and checking their values against the datasheet and the reference manual.

ECitt.648
ECitt.648Author
Associate
October 29, 2019

0690X00000ArPRwQAN.png

Thanks for your answer,

so If I understood correctly the wrong value AF8 should be replaced with AF4 according to the picture.

Thank you

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