Hi, I implemented and tested the example TIM_OCActive, which is included in the STM32Cube_FW_G0_V1.6.2 package, using a NUCLEO-G071RB and the STM32CubeIDE version 1.17.0.
As the trigger signal for the oscilloscope I generated a 10 ms wide pulse by adding lines 3 and 4 in the below code snippet.
Question: although the trigger pulse is written only to the TIM1 CH1 output (PA8), it appears for all four channels, as can be seen in the below oscilloscope screenshot. Please explain that. Thank you!
/* Generate pulse (set/reset) TIM1 CH1 output pin as trigger
* reference for the oscilloscope */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_8, GPIO_PIN_SET);
HAL_Delay(10);
/*## Start signals generation ##*/
/* Start channel 1 in Output compare mode */
if(HAL_TIM_OC_Start(&htim1, TIM_CHANNEL_1) != HAL_OK)
{
/* Starting Error */
Error_Handler();
}
Hello Jan, thank you for your response and question. I appreciate you taking the time for this.
The answer to your question is No., the pulses at channels 1-4 are not present without writing to PA8 (Ch1). Please see the three figures below for details.
- Figure 1. The relevant code snippet and oscilloscope screenshot show the timer 1 signals WITH the 10 ms pulse written to PA8 only (Channel 1). However, the pulse is visible at all four channel outputs.
- Figure 2 shows the code snippet from the original example WITHOUT writing to PA8, and without the 10 ms delay. However, the oscilloscope screenshot shows a 3.3V spike visible at all four channels. The reason for that is unknown. (One might speculate if that spike is caused by the channel 1 output and somehow affects channels 2, 3, 4.)
- Figure 3 shows what you asked for: the code snippet from the original example WITHOUT writing to PA8, but WITH the 10 ms delay. The delay seems to prolong the 3.3V spike.
Is there an answer to my original question why writing to PA8 (CH1) affects all four channels?
Figure 1. Timer 1 signals WITH the 10 ms pulse added only to CH1.
Figure 2. Timer 1 signals WITHOUT the 10 ms pulse (original example code).
Figure 3.
