Showing posts from July, 2010

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…

Kindle DX update blues

A few days ago I received a letter from Amazon stating a new firmware was available for Kindle, and that those with coverage problems with Whispernet could get the update file from the web too.

Firmware update for Kindle is supposed to be quite a straightforward operation. First, update file is downloaded to your Kindle, either wirelessly or manually by the user, to the main folder of the system. Once in there, either because user request or automatically, update process starts.

I've done this before and no trouble happened then. This time was different, though. I mentioned on a previous post that I've played with the USB networking hack, that enables network access to the Linux system running in the Kindle. I did some tests, set the correct system time on my Kindle and forgot about it.

Now that I was trying to update from version 2.3.4 to the new 2.5.2 version I was stucked. Update process stated normally, and "stage 1 of 3" was shown on the lower right corner of the d…

Prepaid data plans in Finland

I've been researching the topic of how to get prepaid data cards for an upcoming trip to Finland. It is said that Finland is one of the cheapest and most competitive wireless communications markets.

Contrary to most people, I just need a temporary solution to get our iPad working while on the go. While most hotels and cities (i.e. Oulu) do have free wifi, I was looking for an alternative to the outrageous roaming cost of Movistar (from 4 to 10 EUR per megabit).
Saunalahti offers a seven-day 4 Mbps data plan for 6.90 EUR. I thought my problem was solved. But just in case, I asked customer service. I learned two things that were a problem: In order to activate the card an SMS had to be sent. Unfortunately, sending an SMS is not one of the things Apple decided you're entitled to do with your iPad. Saunalahti is reserving microSIM cards for contract customers, so if you want pre-paid and microSIM you're out of luck with them. (Apparently you might get lucky in an Elisa shop…

iPad and PDF magazines

I'm a subscriber (and sometimes an author too) of Circuit Cellar magazine. I use to buy it in print format but a few years ago they made the switch to electronic format. Despite the well-know blues about piracy, they chose PDF files with no particular DRM built in. Since then I'm a paying customer.

While I was disappointed with the way the PDF was rendered on Kindle DX, I'm happily surprised that the magazine looks quite nice on iPad. And given the zoom capabilities and the instantaneous response of the device to pan actions I can say it is a very nice experience to read the magazine with it. The only caveat is that sometimes it freezes for a while when browsing the pages quickly. I guess it takes a while to render next page and iPad has limited both computing power and RAM memory.

How to get the PDF file on the iPad is also not obvious. Though there are several PDF viewers for iPad, the ones I've tried do not allow me to add the files I want to view. However, iTunes sof…

My wife has got an iPad

I've been reluctant to give in to the latest Apple gizmo. I tried it out last week and it was ok. Web browsing was smooth and comfortable till you reach a flash based page (flash does not work out of the box). The best feature I noticed was that it dos not get hot. This is very nice when the weather is hot.

Writting tris entry using iPad keyboad proved not to be very convenient, as many words get replaced by others guessed by Safari to be what I want to write. Maybe it is causes by a mismatch between my localization and writing in English here. A simple post like this took me ten minutes and lots of backspace.

Getty Images Settlement Letters in Spain too

Apparently, Getty Images is a company that sells stock photos. The same company you can accept on Flickr to represent your photo portfolio.

As such, it is believed Getty Images make they money by selling stock photos to their costumers, either end-users or designers that use them on their customer's projects.

As any other company dealing with intellectual property, they may have copyright infringement cases every now and then. But here is where the innovation comes: Instead of sending a cease and desist letter to those believed to be infringing upon any right owned by Getty Images, they will just send a "settlement demand letter". The whole purpose of that document is to (1) notify the alleged infringement, (2) to act as an invoice for the amount they claim it is worth the damages for the
previous use of the infringing images (3) to provide erroneous legal claims to confuse addressee (4) to rush recipient to pay without a second thought (5) to offer the licensing of the i…