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Talk to SSD1306 using SPI on Jetson Orin Nano

Driving a small OLED display over SPI from the Jetson Orin Nano's 40-pin header. This covers hardware wiring, device-tree overlay configuration, and a Python test script.

References

1. Hardware Setup

Pin Connections

The SSD1306 OLED has 6 pins. Connect them to the Jetson's 40-pin header as follows:

OLED Pin Function Jetson Pin Header Label
GND Ground Pin 6 GND
VCC 3.3 V power Pin 1 3V3
SCK SPI clock Pin 23 SPI0_SCK
SDA MOSI (data in) Pin 19 SPI0_MOSI
RES Display reset Pin 31 GPIO
DC Data / Command select Pin 32 GPIO
CS Chip Select Pin 24 SPI0_CS0

DC pin

SPI sends a raw stream of bits. The OLED needs to distinguish between commands (e.g. "set brightness to 50%") and pixel data (e.g. "turn on this pixel"). The DC pin provides that signal:

  • DC LOW (0 V) → next bits are interpreted as commands
  • DC HIGH (3.3 V) → next bits are interpreted as pixel data

Typical SPI transaction

  1. Master pulls CS low to select the target device.
  2. Master toggles SCLK and shifts data on MOSI.
  3. Master sets CS high to end the transaction.

Wiring

Connection setup

2. Configure the Device-Tree Overlay

The SPI controller and GPIO pins must be activated via a device-tree overlay. jetson-io.py handles this without manually editing DTS files.

2.1 Check the current boot config

Before making any changes, note the current state of extlinux.conf so we can verify what changed afterwards.

extlinux.conf before changes

2.2 Run jetson-io.py

$ sudo /opt/nvidia/jetson-io/jetson-io.py

2.3 Select Configure Jetson 40pin Header

jetson-io main menu

2.4 Select Configure header pins manually

Configure header pins manually

2.5 Set pin functions

Change the following assignments:

  • Pin 19, 21, 23, 24, 26 → spi
  • Pin 31 → gpio
  • Pin 32 → gpio

Pin configuration

2.6 Save pin changes

Select Back, then Save pin changes.

Save pin changes

2.7 Exit without rebooting

Select Save and exit without rebooting.

Warning

Always verify the config before rebooting. A bad overlay can prevent the system from booting, potentially requiring a full reflash.

Save and exit

3. Verify the Overlay

Check extlinux.conf

Open /boot/extlinux/extlinux.conf and confirm a new JetsonIO section has appeared, referencing jetson-io-hdr40-user-custom.dtbo.

Inspect the overlay (optional)

To read the raw DTS and confirm the SPI and GPIO pins are configured correctly, decompile the overlay:

# Copy the overlay to a working directory
$ mkdir -p ~/workspace
$ cp /boot/jetson-io-hdr40-user-custom.dtbo ~/workspace/

# Install the device-tree compiler
$ sudo apt-get install device-tree-compiler

# Decompile
$ dtc -I dtb -O dts ~/workspace/jetson-io-hdr40-user-custom.dtbo -o ~/workspace/temp.dts

# Inspect
$ cat ~/workspace/temp.dts

The DTS shows the SPI controller node and the two GPIO pins wired to RES and DC.

4. Reboot

$ sudo reboot

5. Run the Python Test

$ git clone git@github.com:rylanpeng/jetson-orin-nano-ssd1306-spi.git
$ cd jetson-orin-nano-ssd1306-spi
$ uv sync
$ uv run python display.py

Result

SSD1306 displaying output