1.8 Embedded programming

The assigment:

Read a microcontroller datasheet and program it in several languages.

Hello Microcontroller / Atmel AVR ATtiny44A datasheet

A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. It is different from a microprocessor in that a microcontroller includes a CPU, a fixed amount of RAM, ROM and other peripherals all embedded on a single chip.

I am using the Atmel AVR ATtiny44A in the Electronics Design assignment and its datasheet is on this document (.pdf). There is a curious think about the real meaning of the AVR acronym, read on Wikipedia

There is a guide of the pins from the High-Low Tech Group at the Media Lab:

I also found really interesting this guide because explains in a simple way how microcontrollers work Beginning Embedded Electronics - 1 / Lecture 1 - Background and Power Supply

Ingredients

Physical stuff (Atoms)

Hello echo world 0.2 (Modified at Electronics Design)

USB TTL Serial Cable. 6 way, 0.1" pitch single inline connector

FabISP Fabable In-System-Programmer (made on Electronics Production)

6-Pin DIL Ribbon Cable, 3 Inch

USB Mini-B Cable - 6 Foot

Digital stuff (Bits)

• source code
• makefile

Instructions to program in C using GNU Make and avrdude

Steps

Step 0: Connect the physical components. Result: Circuit connected

It is necesary to conect all the components as indicated on the diagram.

Step 1: Configure the microcontroller to run at 20 MHz. Result: Microcontroller @20Mhz

Run the following command on the terminal: sudo make -f hello.ftdi.44.echo.c.make program-usbtiny-fuses

Observation: In case you are using the AVR ISP mkII, then the command is sudo make -f hello.ftdi.44.echo.c.make program-avrisp2-fuses

There is an error on the line 216 of the C source code, it must be added the const as on the image.

The program will respond with a Fuses OK. Thats the signal that everything went fine. If not, check your board first.

Step 2: Program the microcontroller with the C code using the makefile. Result: Microcontroller programmed.

sudo make -f hello.ftdi.44.echo.c.make program-usbtiny if you are using the FabISP

sudo make -f hello.ftdi.44.echo.c.make program-avrisp2 if you are using the AVR ISP mkII

Step 3: Open a serial monitor (in GNU/Linux there is a Serial port terminal or use the Arduino IDE). Configure the port connection to your USB port (in case of GNU/Linux could be /dev/ttyUSB0 or /dev/ttyACM0, check using: ls /dev/tty* on your terminal) and configure the baud rate to 115200. Result: Program ready to read the serial port

Step 4: Type some characters using the keyboard and over the serial monitor program (or the program you are using). Result: The microcontroller will reflex every character inputted.

Instructions to program the microcontroller with the Arduino IDE

Steps

Step 0: Connect the physical components. Result: Circuit connected

It is necesary to conect all the components as indicated on the diagram.

Step 1: Install the ATtiny libraries for Arduino IDE previously downloaded from Github . Result: Arduino IDE capable of programming the ATtiny microcontroller

Inside your sketchbook folder create a new one called hardware and decompress all the content of the master.zip file:

Step 2: Set some parameters on your Arduino IDE. Result: IDE ready to program the microcontroller inside the circuit board.

Tools-->Board-->ATtiny44 (external 20Mhz)

Tools-->Serial Port-->/dev/ttyUSB0 (Depends on your operating system, on GNU/Linux use ls /dev/tty* to discover your port list and select accordingly)

Tools-->Programmer-->AVRISP mkII (depends on the ISP used)

Step 3: Load, verify and upload your source code from the Arduino IDE to the microcontroller's circuit board. Result: Source code loaded in the microcontroller.

In GNU/Linux, after you try to upload the code to the microcontroller sometimes is required some aditional activities.

First create a rule inside /etc/udev/rules.d/, it can be named: 10-usbtinyisp.rules and is necesary to add this line only: SUBSYSTEM=="usb", ATTR{product}=="USBtiny", ATTR{idProduct}=="0c9f", ATTRS{idVendor}=="1781", MODE="0660", GROUP="dialout"

After that, execute the following command on the terminal: sudo udevadm trigger (this forum provides more related information)

Step 3: Be sure that your source code was uploaded correctly from the Arduino IDE to the microcontroller's circuit board. Result: Source code loaded in the microcontroller.

The message area from the Arduino IDE will display: Done uploading.

Because of the code loaded, every time the button is pushed, the LED will change it state from ON to OFF and viceversa.

Results:

The board previously designed was programmed. The microcontroller now has a code inside that makes that every input read over the serial port will be returned to the computer using the same port.

Inspirations from HTMAA

• Sam Calisch

Full visual journey