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…

Simple schematics on the web

I wanted to create a simple schematic for my students. I could use an electronic CAD system but I needed something simple and quick. I look it up on the Internet and I have found a few choices. The first one was from Digi-Key and it worked nicely for my job as shown below (you may want to click on the image to get it to readable size).

It was documenting the circuit of a simple electrostimulator to be used with an Arduino for creating some pain. One of my students wanted to build an Arts installation will cause him physical pain and this one fits the bill. For the rest of the people, the usual disclaimer is in place: use it at your own risk.


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