Pi user space SPI

I finally had some time to play with a OLED (same one as my I2C one; SSD1306 chip), but this interface was SPI. I wanted to learn more about SPI and write a user space program in C++ that would run on my Raspberry Pi and drive the SPI OLED just like I had done for my I2C OLED. Did some digging on spidev and learned a lot. The commands to the OLED were the same as the I2C so I did not have to re-invent the wheel there, but the communication was the only difference.

Beaglebone Black with 128x64 OLED

I compiled my I2C OLED library on my beaglebone black and with little effort, I was able to get it working. My BBB is running Ubuntu instead of Angstrom (instructions to get that flashed are in a previous post). This code was the same one running on the raspberry pi in my prior posts.

Steps taken were:

1. Download code from github
2. run make
3. run the compiled executable

The I2C class was defaulted to use the address of the OLED so I didn't need to change anything. :)

Here are some images of displaying a BMP on the OLED.

Raspberry Pi GPS and LCD

Building upon the I2C and OLED from my previous posts, I connected a GPS and used the same OLED to display data. Currently, latitude, longitude, speed, and course are the values I chose to deal with first, but gpsd has much more data you can get at. I chose to do all my development with C++, but a quick google search shows many examples using Python. Once I get my C++ code working and finalized, I'll port things to Python.

The OLED is connected via I2C to the Raspberry Pi and the GPS is using the hardware UART on the Pi. The hard part is now out of the way! Next up, save the GPS data (in KML) to a file and plot that file on Google Earth.

Raspberry Pi and 128x64 OLED

I recently purchased a LCD display for some projects I have going. Initially, I hooked it up to my arduino since Adafruit has libraries already written that can let you run things easily (just has to solder the header pins to the PCB and you are in business). Their library support is great and it makes things easy to use and they have some working examples too. Unfortunately (or fortunately!), if you plan to use this for a Raspberry Pi or Beaglebone Black, you are not so lucky as there are no libraries that you can download and use for those (yet!). Since I wanted to learn more about interfacing with hardware/firmware, this was a great place to start. The driver chip on the OLED board is a SSD1306 one and the datasheet is available here. I have mine connected to the PI via I2C. Note, by default, the OLED comes with SPI enabled, so closing 2 gates on the back with a little solder needs to be done to enable I2C. Just using a 2 jumper wires for clock and data, we are in business!

I was able to get some simple text up on the LCD and played around with placement (ie. centered and left justified). For me, it was easier to develop on ubuntu and copy my files over to the PI. It allowed me to do remote debugging and my core i7 was much faster than the processor on the PI. I still have a bit more functionality to add but so far it has been an enjoyable project to work on.