WEEK 8: EMBEDDED PROGRAMMING

This was probably the most challenging week so far, as programming has always been a black box I´ve been scared of. The week started with Neil´s “1 hour knowledge capsule” about embedded programming, and I have to admit that my brain was about to explode with so many a-priori unconnected new terms and jargon. After a week of fighting “the monster” (embedded programming) I´m happy to say that I feel like I have a much better idea of what is going on when dealing with those “black chips that lets us do fancy stuff”.

This week I navigated more class pages than ever. I especially found Pip´s tutorial very useful http://fab.cba.mit.edu/classes/863.12/people/pip/WK7/wk7.html. The schematic below is just wonderful.

Neil said in class that how we manage Mercurial (Tortoise or terminal) would tell how we will manage embedded programming. I´m honestly terrified by the terminal, that´s why I started with Arduino IDE first.

Hasier´s option 1: using Arduino´s IDE to program the board

It was extremely gratifying to program the board so quickly using this tutorial from high low tech. http://hlt.media.mit.edu/?p=1695. The basic idea is to burn Arduino´s bootloader into the chip, so that we can upload programs using Arduino´s simple IDE.

I know this is probably the easy-cheap way, and not the most code-efficient way of doing it, but I was just so happy when the led started working.

I changed the code a bit in order to activate the led with the button. I had to be careful of selecting the pins for the switch and led.

My FabIsp worked perfectly. There was only one small mistake with the host board. I had not added the pullup resistor (this is when I understood why there were so many back and forth emails about this in the past weeks). I knew the chip had an internal pull up resistor, but I did not know this was not activated by default. I did not know how to do that, but luckily enough I found out I could solder a resistor “neatly” on the board.

At this point I already had decided that the arduino IDE workflow was gonna be the chosen one for the rest of the semester, but I decided to give it a try to the pure c path in order to get a better grasp of it (which may be very useful for the future).

Hasier´s option 2: programming directly the .c and .c.make files

This is where Pip´s tutorial was extremely useful.

By the way, find evidence below of my willingness to go over the microcontroller datasheet. I printed the whole thing, but I have to admit that I had a very hard time.

Luckily enough, I´m taking Paul Horowitz´s class at Harvard (Physics 123), so hopefully I will be able to go over the datasheet and understand something sooner than later. We are starting to build a computer from scratch there.

Back to the assignment, I took Pip´s .c and .c.make files and make some changes in order to get a simple button controlled led. The process of compiling and uploading was not bad at all. You just need to download crosspack (for mac) and ftdi chip drivers, and then go to the terminal , find your folder (using command cd and ls) and type:

make -f blinking.led.c.make

sudo make -f blinking.led.c.make program-usbtiny-fuses

sudo make -f blinking.led.c.make program-usbtiny

Done. The uploading process is as easy as the Arduino IDE. The problem is on the code, that is pretty hard to decipher for a beginner like me.

DECISION: being realistic about the time left for the end of the semester and understanding the learning curve of each method, I´m gonna use the arduino IDE workflow for now.

Also, I realized that I will be short of pins for my final project, so I started fabricating a fab version of the arduino