In this blog post I’m going to discuss how to connect a Raspberry Pi to an Arduino via USB and then communicate between them serially. If you want to communicate between an arduino and an RPI using I2C, see this older post:. In my last post, I did the same thing, except communicating between a PC and an Arduino serially. For this project, the arduino is configured exactly the same and running exactly the same software as it was in my prior post. The basic idea of the project is to communicate with an Arduino that has a switch, motion detector, and LED on it. The RPI sends commands to the arduino to read the status of the switch and motion detector and to turn the LED on and off. The RPI will first look at the switch.
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If it is on, then it will look at the motion detector. If motion has been detected then the RPI will tell the arduino to turn on the LED. If not, it will request the LED be turned off. You will want to look at the prior post to see how the hardware is setup and how the software works as I literally moved the software from the PC to the Raspberry Pi, made a couple of tweaks and it runs as it did in on the PC.
The Arduino-PC post can be found here:. When I wrote the software that runs on a PC, it was my hope that it would require minimal changes to migrate to a Raspberry Pi. Turns out it was VERY easy. Free Pascal’s ability to move effortlessly between platforms proves itself again.
I had to tweak the serial library to remove a few constants not found on the RPI. Within my own code, I needed to remove the calls to the windows multimedia library call and handle abnormal program termination (explained later). Getting the Hardware Connected I was not sure exactly how I was going to access an arduino serially from the RPI. Everything I read indicated I would need to use the RPI’s serial port on its the GPIO pins. I really was hoping I could just use the RPI’s USB port. Download subtitle indonesia inuyasha movie. I found the answer on Oscal Liang’s blog: Before you connect the arduino to the RPI via the USB port do this: Type lsusb to see what USB devices are currently present: Now type ls /dev/tty* to see what serial ports are currently defined: Now connect the Arduino to the RPI via the USB port.
Again type lsusb to verify the arduino is now being seen by the USB drivers: and again type ls/dev/tty* to find out what device has been added. This will be the serial port we will be accessing from the RPI’s pascal program: As you can see by the lsusb command, the arduino is being seen by the RPI and the tty device for the serial port is named /dev/ttyACM0. That was, to me, amazingly simple.
I was expecting there to be a lot more involved in getting serial access to an USB port via Linux. Testing the Hardware Everything appears to be running, now let’s make sure we can really communicate. First, download, compile, and install the Arduino’s software (the link is at the end of this post). Once that is done, the Arduino will be expecting valid packets from the RPI.