Moving code from ESP8266 to ESP32

A while ago I made a mashup of Dan Royer's code CNC 2 Axis Demo with my own code for trapezoidal motion stepper and servo control for ESP8266.

I assumed porting the code to the ESP32 would be trivial, and that was true for the most part: changes like library name being Wifi.h instead of Wifi8266.h were not a problem. UDP now does not like multicharacter writes but you can use print instead. So far so good.

However, when it came to the interrupt code I was stuck with the stepper interrupt causing an exception sometimes. And to make things weirder, the servo interrupt worked flawlessly (both of them had the IRAM_ATTR directive if you ask me).

Going little by little, I could narrow down the culprit to a floating point operation during the interrupt, that would cause problems sometimes but not always. Browsing around I found this post. Where the solution was simple: do not use floats within the interrupt routines but doubles. The reason was the float calculation would be performed by…

Servo control on ESP32

One of the things that do not work the Arduino way in the ESP32 so far is the PWM generation using analogWrite() command. There is, however, a library to handle PWM signals using timers, so up to 16 PWM signals can be handled.  You can find fine examples like this one.

However, I wanted to use timers in my project and I wanted to have a clearer view of what was going on, so I decided to handle the PWM timing myself. Here you have an example of how to handle a single servo using a timer. Same timer and routine could be extended to handle more output pins in a similar fashion, but I just needed one here.

It is just a simple sketch that moves the servo back and forth using a sin function to get this motion easily, ranging the signal pulse width from 600 to 2200 microseconds.

This is the end result:

All in all, I am impressed with the simplicity and power of the ESP32 and the great Arduino-esp32 code. Kudos to Espressif.


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