ESP32 Forum

Posted: **Thu Jun 20, 2024 11:44 am**

Hi,

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

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

Posted: **Thu Jun 20, 2024 1:45 pm**

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 563 times

Posted: **Thu Jun 20, 2024 2:11 pm**

marsal64 wrote: ↑
Thu Jun 20, 2024 11:44 am
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.

ESP32 Forum

GPIO pulse generated - inconsistent width

GPIO pulse generated - inconsistent width

Re: GPIO pulse generated - inconsistent width

Re: GPIO pulse generated - inconsistent width