Showing posts from May, 2014

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…

Mobile data services for Japan visitors

On the occasion of a trip to Japan, I had to look for a way to stay connected while on the go. Though most hotels will offer free wifi to guests, having an Internet connection while trying to navigate the city is most welcome. And if you are to believe the claim, Tokyo is the most populated city of the world. It certainly has an impressive public transportation system with many different companies just for the light trains and underground systems.

Google Maps seems to be properly in synch with local companies schedules and provided accurate results on how to go from point A to point B within the city. But to be able to use it you need Internet mobile access. And this is where Japan seems a bit odd for the visitor: It seems you cannot buy a prepaid voice or data SIM card unless you are Japanese. Maybe I am missing something here but that was what I learned from my online search.

One notable exception seems to be B-mobile VISITOR SIM, which offered pre-paid data service SIM card.