TIM3 partial remap for PWM on pin PB5 and conflict with I2C1

[kwiatkowski]

Posted on February 27, 2012 at 10:42

I have the following situation:

- I have a STM32F103RB processor. - Timer 3 configured to generate a PWM signal at the output of PB5. I had to use partial_remap and channel 2 of the timer. Up to this point everything is working properly. - The situation changes if the clock is attached to the I2C1. At this point I have a problem because the output PWM signal PB5 disappears. I do not need no alternate functions for the I2C on this pin. How can I solve this problem? #read-the-errata #tim3-partial-remap-pwm-pb5-i2c1

[Tesla DeLorean]

Posted on February 27, 2012 at 17:17

From the ERRATA document

2.4.8 I2C1 and TIM3_CH2 remapped Conditions �? I2C1 and TIM3 are clocked. �? I/O port pin PB5 is configured as an alternate function output. Description Conflict between the TIM3_CH2 signal and the I2C1 SMBALERT signal, (even if SMBALERT is not used). In these cases the I/O port pin PB5 is set to 1 by default if the I/O alternate function output is selected and I2C1 is clocked. TIM3_CH2 cannot be used in output mode. Workaround To avoid this conflict, TIM3_CH2 can only be used in input mode.