Using I2C OLED Display#
Using I2C on BeagleY-AI is similar to using it on any Raspberry Pi compatible board. The image below shows the BeagleY-AI I2C pinout. For more information check pinout.beagley.ai/pinout/i2c.
OLED (ssd1306) displays#
Wiring/connection#
Following the I2C pinout shown above let’s make the connection of our OLED display with BeagleY-AI.
Connection for both 128x64
and 128x32
resolution displays are demonstrated in the images below:
To check if your OLED is correctly connected to your BeagleY-AI you
can use i2cdetect
command as shown below.
i2cdetect -y -r 1
The above command should show 3c
address occupied in the output, which is the default I2C address of our OLED display.
debian@BeagleBone:~$ i2cdetect -y -r 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Using kernel driver#
To use the kernel driver to drive the SSD1306 oled, we have created an overlay /boot/firmware/overlays/k3-am67a-beagley-ai-i2c1-ssd1306.dtbo
.
To load the overlay you have to add fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ssd1306.dtbo
to /boot/firmware/extlinux/extlinux.conf
as shown below.
Note
Current overlay is created for 128x64 OLED displays, you can update the overlay to use it for other resolution OLED displays.
...
...
...
label microSD (default)
kernel /Image
append console=ttyS2,115200n8 root=/dev/mmcblk1p3 ro rootfstype=ext4 resume=/dev/mmcblk1p2 rootwait net.ifnames=0 quiet
fdtdir /
fdt /ti/k3-am67a-beagley-ai.dtb
fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ssd1306.dtbo
After rebooting the board you should see /dev/fb0
available.
debian@BeagleBone:~$ ls /dev | grep fb
fb0
To show random noise on the display you can use /dev/urandom
and feed it to /dev/fb0
,
cat /dev/urandom > /dev/fb0
To show blank screen you can use /dev/zero
and feed it to /dev/fb0
,
cat /dev/zero > /dev/fb0
To fill the screen with white pixels you can create a python script
called fill-oled.py
to create data.out
file and feed it to /dev/fb0
,
nano fill-oled.py
Copy paste the below code to fill-oled.py
,
xsize = 128
ysize = 64
with open('data.out', 'wb') as f:
for y in range(0, ysize):
for x in range(0, xsize):
pixel = 255
f.write((pixel).to_bytes(1, byteorder='little'))
To get the data.out
from fill-oled.py
file execute the command below,
python fill-oled.py
The above command should create a file called data.out
.
To feed data.out
to /dev/fb0
execute the command below,
cat data.out > /dev/fb0
Todo
Add instructions to use OLED for console and printing text via /dev/fb0
interface.
Setup ssd1306 linux software#
There are several examples available online to use OLED (ssd1306) displays under linux.
We are using ssd1306_linux from armlabs
to
demonstrate how you can write to an OLED (ssd1306) display.
Tip
For detailed usage examples of the library check Examples section of the Readme.
Note
If you tried Using kernel driver, you must remove the
fdtoverlays /overlays/k3-am67a-beagley-ai-i2c1-ssd1306.dtbo
line from
/boot/firmware/extlinux/extlinux.conf
and reboot
your BeagleY-AI board
before following the instructions provided below.
Clone the ssd1306_linux
github repository on your BeagleY-AI.
git clone https://github.com/armlabs/ssd1306_linux.git
Change directory to your cloned ssd1306_linux
github repository.
cd ssd1306_linux
Execute make
to build the binary to control your I2C OLED display.
make
Now, you should have ssd1306_bin
binary file generated in the folder that you can use to easily
write text on you I2C OLED (ssd1306) display.
Example1: Hello World!!!!#
let’s create a script inside the repository (ssd1306 folder) to print Hello World!!!!
on the screen.
nano hello-world.sh
Now copy paste the code shown below in your hello-world.sh
file. Update the code if your display resolution
is not 128x64
, comment out first line and uncomment second line to choose 128x32
display size.
./ssd1306_bin -n 1 -I 128x64
#./ssd1306_bin -n 1 -I 128x32
./ssd1306_bin -n 1 -c
./ssd1306_bin -n 1 -r 0
./ssd1306_bin -n 1 -x 1 -y 1
./ssd1306_bin -n 1 -l "Hello World!!!!"
Execute the hello-world.sh
script using command below,
source hello-world.sh
Executing the command above should print Hello World!!!!
on your OLED display.
Understanding the code#
./ssd1306_bin -n 1 -I 128x64 ①
#./ssd1306_bin -n 1 -I 128x32 ②
./ssd1306_bin -n 1 -c ③
./ssd1306_bin -n 1 -r 0 ④
./ssd1306_bin -n 1 -x 1 -y 1 ⑤
./ssd1306_bin -n 1 -l "Hello World!!!!" ⑥
① Use this command to set OLED display resolution to 128x64
② Use this command to set OLED display resolution to 128x32
③ Clear the display
④ Set rotation to 0/normal
⑤ Set cursor to location x:1 y:1
⑥ Write Hello World!!!!
to display as line using -l
command.
Note: We are using -n 1
because our OLED display is connected to /dev/i2c-1
port.
Example2: Date and time#
To print the date and time on our OLED screen we will be using date
command but you
can also use hwclock
command to show date and time from onboard RTC. For details on using
date
and hwclock
you can check Using the on-board Real Time Clock (RTC) demo.
Let’s create date-time.sh
in the same folder.
nano date-time.sh
Now copy paste the code shown below in your date-time.sh
file. Make sure to update the code if your display resolution
is not 128x64
, comment out first line and uncomment second line to choose 128x32
display size.
./ssd1306_bin -n 1 -I 128x64
#./ssd1306_bin -n 1 -I 128x32
./ssd1306_bin -n 1 -c
./ssd1306_bin -n 1 -r 0
while :
do
./ssd1306_bin -n 1 -x 1 -y 1
./ssd1306_bin -n 1 -f 1 -m "$(date +%Y:%m:%d)\n\n$(date +%H:%M:%S)"
done
Execute the date-time.sh
script using command below,
source date-time.sh
Executing the command above should print Date & Time
on your OLED display.
Understanding the code#
./ssd1306_bin -n 1 -I 128x64 ①
#./ssd1306_bin -n 1 -I 128x32 ②
./ssd1306_bin -n 1 -c ③
./ssd1306_bin -n 1 -r 0 ④
while : ⑤
do
./ssd1306_bin -n 1 -x 1 -y 1 ⑥
./ssd1306_bin -n 1 -f 1 -m "$(date +%Y:%m:%d)\n\n$(date +%H:%M:%S)" ⑦
sleep 0.2 ⑧
done
① Use this command to set OLED display resolution to 128x64
② Use this command to set OLED display resolution to 128x32
③ Clear the display
④ Set rotation to 0/normal
⑤ Run infinite loop to regularly update screen.
⑥ Set cursor to location x:1 y:1
⑦ Write Date and Time
to display on separate lines as message using -m
command.
⑧ Sleep for 200ms (200 milli seconds)
Note: We are using -n 1
because our OLED display is connected to /dev/i2c-1
port.
Tip
Other I2C devices can also be connected and used with BeagleY-AI in the same way shown in this demo.