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WSAL22026 – RS485 CAN for Jetson Nano/en

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Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

Summary

Technical guide for configuring SPI, CAN and RS485 on the Waveshare expansion board for the NVIDIA Jetson Nano.

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Technical overview

  • The board includes an MCP2515 CAN controller over SPI and an SP3485 RS485 transceiver over UART.
  • A standard 40-pin GPIO header allows direct attachment to the Jetson Nano.
  • Digital isolation circuitry and TVS protection improve stability and guard against surge voltages.
  • SPI must be enabled by modifying the device tree; updating only the dtb partition is not supported, so a full system re-flash is required.
  • CAN demo: connect the hardware module, then run cantest.py at a 500 Kbps baud rate.
  • RS485 demo: connect the hardware module, ensure UART is free, and run rs485test.py.

Commands and examples – verify before use:  

sudo apt-get install minicom
sudo apt-get install python-pip nano
sudo pip install pyserial
sudo pip install spidev==3.1
sudo mkdir sources_nano
cd sources_nano
sudo mv ~/Downloads/Jetson-210_Linux_R32.7.2_aarch64.tbz2 ~/sources_nano/
sudo mv ~/Downloads/Tegra_Linux_Sample-Root-Filesystem-R32.7.2_aarch64.tbz2 ~/sources_nano/
tar -xjf Jetson-210_Linux_R32.7.2_aarch64.tbz2
cd Linux_for_Tegra/rootfs/
tar -xjf ../../Tegra_Linux_Sample-Root-Filesystem-R32.7.2_aarch64.tbz2
cd ../
sudo ./apply_binaries.sh
sudo apt-get install -y device-tree-compiler
cd kernel/dtb
sudo dtc -I dtb -O dts -o tegra210-p3448-0002-p3449-0000-b00.dts tegra210-p3448-0002-p3449-0000-b00.dtb
sudo cp tegra210-p3448-0002-p3449-0000-b00.dts tegra210-p3448-0002-p3449-0000-b00-bak.dts
sudo nano tegra210-p3448-0002-p3449-0000-b00.dts
sudo dtc -I dts -O dtb -o tegra210-p3448-0002-p3449-0000-b00.dtb tegra210-p3448-0002-p3449-0000-b00.dts
sudo ./flash.sh jetson-nano-emmc mmcblk0p1

Notes and version constraints

  • Device tree modifications are version-sensitive (verified for JetPack 4.6.2). Mistakes may prevent the system from booting.
  • Updating only the dtb partition is not supported; a full system re-flash is required.
  • Boot configuration must be redone after flashing.
  • Ensure UART is not in use before running the RS485 demo.
  • The maximum supported CAN baud rate is currently 500 Kbps; higher rates such as 1000 Kbps are not supported.

Source and revision record

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