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Showing posts from March, 2016

Moving code from ESP8266 to ESP32

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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…

Software I2C for Arduino

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While the Wire library allows you to get I2C working right off the bat with Arduino, there are times when the built-in Wire library does not do it. For some people this happens because they need to do a repeated start condition or to receive a large number of bytes, tasks that seemed to be not possible with Wire library. But for me the problem this time is a bit odd: I had to overcome the limitation of each I2C device to have a different address.

It turns out that I am using a magnetic encoder chip that responds to a given address that cannot be changed. Because I want to be able to access at least two similar encoders from on Arduino board I find myself in the unlikely situation where I have to use two different I2C buses, one per device. However, I2C interface was designed to do the exact opposite thing, allowing several devices to communicate over the same bus (provided each one had a different address of course).

As second detail I have been interested is to speed up the communica…

Crome 49 broke PDF viewing in Mavericks

A recent update of Chrome brought me some trouble with various web content, including PDF viewing. Apparently some change in how layers are handled makes the viewing of PDF content almost impossible: you see some bars of the underlying PDF file but only as a flicker while you scroll down the document, as if some black layer was on top of it.

A quick check online revealed that many people using OSX versions before El Capitan were complaing about exactly that same thing.  And while Google seemed not to be offering a solution at the moment (and upgrading to El Capitan was not something I would like to do right now) some users suggested that disabling hardware acceleration in the browser would help.

However, disabling hardware acceleration might solve this issue but create other problems with other content or just degrade browsing performance, so I did not want to go that way either.

Finally, another user suggested the install of a browser extension (in fact replacing Chrome's built-i…