关于Pico i.MX7D CANbus支持、引脚复用及Android Things代码的问询

Great question—this is a common point of confusion with multi-function GPIO pins on single-board computers, especially when cross-referencing different documentation sources. Let’s break this down clearly:

Are These Pins Multi-Function? #

Absolutely. The Raspberry Pi Pico’s RP2040 chip is built with pin multiplexing—many physical pins can be configured to serve different hardware roles beyond basic GPIO.

• Pins 16 & 18 are mapped to CAN0_TX and CAN0_RX (for the board’s first CAN controller)
• Pins 38 & 40 correspond to CAN1_TX and CAN1_RX (for the second CAN controller)

Android Things labels them as GPIO because that’s their default boot state. The OS doesn’t expose CAN functionality out of the box, but you can reconfigure these pins to use their CAN capabilities via low-level system commands or custom driver code.

Has Anyone Developed CAN Bus Code for Android Things on Pico? #

While Android Things has limited official support for the Pico’s CAN controllers, the developer community has explored workarounds. Here’s what you need to know:

• Core Implementation Approach: Most working solutions rely on combining SocketCAN (Linux’s standard CAN interface) with pin multiplexing configuration. A high-level workflow looks like this:

  1. Reconfigure target pins from GPIO to CAN mode via sysfs. For example, you might run shell commands like:

     # Set pin 16 to CAN0_TX function
     echo can0_tx > /sys/class/gpio/gpio16/function
     # Set pin 18 to CAN0_RX function
     echo can0_rx > /sys/class/gpio/gpio18/function
     

     Note: Exact sysfs paths and function names may vary—you’ll need to reference your specific Android Things build’s RP2040 sysfs documentation.
  2. Load required CAN kernel modules (if they aren’t preloaded in your Android Things image)
  3. Configure the CAN bus bit rate (e.g., ip link set can0 type can bitrate 500000)
  4. In your Android Things app, implement communication using either:
     • JNI to call Linux SocketCAN APIs directly from C/C++
     • Community-developed Java wrapper libraries that interface with SocketCAN (no official Google support exists for this)

• Community Proof-of-Concepts: Several developers have shared working CAN implementations for Android Things on RP2040-based boards. These often involve minor kernel tweaks or user-space tools to enable the CAN controller, so adapting existing SocketCAN tutorials to the Android Things environment is a solid starting point.

内容的提问来源于stack exchange，提问作者Matt Chamberlain