This is a follow up article to Arduino and the Raspberry Pi
Now that your RPi has all the needed software
You should now wire up your arduino similar to how it’s done here. You can skip the part about using the 5V linear regulator because we’re going to use the ground and the 5V line directly from the GPIO pins available on the raspberry pi. Use the GPIO pin out documentation here for guiding yourself where the pins are. It helps to use a multimeter to ensure you have the proper 5V line hooked up.
Alternatively, you can buy a prototyping shield from adafruit where the pins are already broken out for you. All you need to do is locate the tx, rx, 5v, and gnd lines. It also helps to map down at least one digital io pin that we’ll be using as a fake DTR pin.
Finally, you’ll need something like a logic level converter before you wire up any pins to the arduino because most of the pins on the raspberry pi operate at a 3.3v level and your arduino uses 5v. The logic level converter makes it really easy to hook up 3.3v lines that will directly convert to 5v lines, and will support the signal in both directions (so if your signal goes low on the 5v side, it will also go low on the 3.3v side, and vice versa)
Here’s what my board looks like wired up. The power rails on the left side of the breadboard are 3.3v, and the rails on the right side are 5v. B1 on the logic level converter is hooked up to D0 on the arduino, B2 is hooked up to D1, and B3 is hooked up to RST. A1 on the logic level converter is the 3.3 equivalent of B1. A1 hooks up to TX on the raspberry pi gpio pins, and in this case it is pin 8 on the header. A2 hooks up to RX which is pin 10 on the header.
Preparing your environment
Now when you upload code to the arduino on the command line, you should create an empty directory where you’ll store your code. For our examples, lets call this directory “mysketch”. You’ll also need to copy a sample Makefile that contains all the necessary logic for uploading sketches. You can find this “Makefile” in the base arduino package that you installed. We’ll run “dpkg -L arduino-mk” to find out where this file is located:
root@raspberrypi:~# dpkg -L arduino-mk /. /usr /usr/bin /usr/bin/ard-parse-boards /usr/share /usr/share/arduino /usr/share/arduino/Arduino.mk /usr/share/man /usr/share/man/man1 /usr/share/man/man1/ard-parse-boards.1.gz /usr/share/doc /usr/share/doc/arduino-mk /usr/share/doc/arduino-mk/copyright /usr/share/doc/arduino-mk/changelog.Debian.gz /usr/share/doc/arduino-mk/arduino-cli.html /usr/share/doc-base /usr/share/doc-base/arduino-cli
The file we’re looking for is called Arduino.mk. Copy this file to your mysketch directory and rename it “Makefile”
cp /usr/share/arduino/Arduino.mk ~/mysketch cd ~/mysketch mv Arduino.mk Makefile
You’ll need a few environment variables set properly so that the tools know where your arduino is hooked up. You should probably add these to your .bashrc or .profile file so that they will be there the next time you login:
export BOARD=uno export SERIALDEV=/dev/ttyAMA0 export ARDUINO_PORT=/dev/ttyAMA0 export ARDUINO_DIR=/usr/share/arduino
Unless you’re using a different distro or arduino bootloader version, these parameters will probably be identical for you.
Next you’ll create your arduino code which should have a file that end in “.ino”. When you list the contents of the directory, you’ll have 2 files in there, the Makefile we copied over, and your arduino sketch:
root@raspberrypi:~/# cd mysketch root@raspberrypi:~/mysketch# ls Makefile blink.ino
Sending code the the arduino is simple. Simply run the command “make upload” and it will compile your .ino file into a hex file that will be sent to the arduino using a tool called avrdude. Since you’re running this on the command line, you’ll see all the commands run by the Makefile when you run “make upload”.
root@raspberrypi:~/mysketch# make upload Makefile:535: build-cli/depends.mk: No such file or directory echo '#include <Arduino.h>' > build-cli/blink.cpp cat blink.ino >> build-cli/blink.cpp /usr/bin/avr-g++ -MM -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=100 -I. -I/usr/share/arduino/hardware/arduino/cores/arduino -I/usr/share/arduino/hardware/arduino/variants/standard -g -Os -w -Wall -ffunction-sections -fdata-sections -fno-exceptions build-cli/blink.cpp -MF build-cli/blink.d -MT build-cli/blink.o cat build-cli/blink.d > build-cli/depends.mk rm build-cli/blink.cpp cat build-cli/blink.d > build-cli/depends.mk for STTYF in 'stty -F' 'stty --file' 'stty -f' 'stty <' ; \ do $STTYF /dev/tty >/dev/null 2>&1 && break ; \ done ; \ $STTYF /dev/ttyAMA0 hupcl ; \ (sleep 0.1 2>/dev/null || sleep 1) ; \ $STTYF /dev/ttyAMA0 -hupcl echo '#include <Arduino.h>' > build-cli/blink.cpp cat blink.ino >> build-cli/blink.cpp /usr/bin/avr-gcc -mmcu=atmega328p -Wl,--gc-sections -Os -o build-cli/mysketch.elf build-cli/blink.o build-cli/libcore.a -lc -lm /usr/bin/avr-objcopy -O ihex -R .eeprom build-cli/mysketch.elf build-cli/mysketch.hex /usr/bin/avrdude -q -V -p atmega328p -C /etc/avrdude.conf -c arduino -b 115200 -P /dev/ttyAMA0 \ -U flash:w:build-cli/mysketch.hex:i done with autoreset avrdude-original: stk500_recv(): programmer is not responding
You might see the error message above: “programmer is not responding”. This is because one must temporarily flip the reset pin on the arduino before code can be uploaded. When we wired up the arduino, it was hooked up to one of our GPIO pins. It’s possible to manually flip this pin every time you upload code, but you’ll need to have great reflexes.
How do we fix the DTR pin?
Visit the next article in the series for auto-magically flipping the DTR pin