GPIO pulse generated - inconsistent width

[marsal64]

Hi,

using ESP32-S3 at 160MHz, I run once per some seconds the code:

Code: Select all

gpio_set_level(GPIO_NUM_36, 1);
gpio_set_level(GPIO_NUM_36, 0);

My app runs WiFi, UART and two other lightweight FreeRTOS tasks.

I observe non-consistent width of the "pulse" I generate on GPIO_NUM_36 pin:
Typically: 6.6uS
Sometimes: 1.275uS
Rarely: 3.3625uS

Could please anybody explain what is happening here?

Thank you

[ok-home]

Hi
bitbang on esp32 gives unpredictable results
- interrupts (wifi,freertos...)
- cache misses
- .....
as an example simple code

Code: Select all

 
 gpio_set_level(GPIO_BLINK, 1); 
 gpio_set_level(GPIO_BLINK, 0); 
 .........
 gpio_set_level(GPIO_BLINK, 1); 
 gpio_set_level(GPIO_BLINK, 0); 
 ............ 
 GPIO.out_w1ts = mask; 
 GPIO.out_w1tc = mask; 
 ........... 
 GPIO.out_w1ts = mask; 
 GPIO.out_w1tc = mask; 

when code in flash memory and IRAM and the process of swapping cache from flash memory

bitbang.JPG (96.03 KiB) Viewed 565 times

[MicroController]

Code: Select all

gpio_set_level(GPIO_NUM_36, 1);
gpio_set_level(GPIO_NUM_36, 0);

Could please anybody explain what is happening here?

Likely: Caching, possibly: synchronization of the CPU with the APB and the GPIO peripheral.
You can look into Dedicated GPIO to improve the latter, and put code into IRAM to avoid cache issues.