teensy4-rs hardware and driver support

[Nbelles]

Hey all,

I've been using the Teensy 4.1 for a few years now with the Teensyduino architecture and am quite familiar with it. I have a decent-sized project (~20K lines of cpp, not including external libraries) built on Teensyduino that I'd really like to migrate to rust but I'm concerned about the level of difficulty to make that happen given the current reliance on external libraries. I'm happy to commit a couple months of time to making it happen but I want to know that it's possible given I'm a beginner in rust. The project currently utilizes a few hardware peripherals that are necessities for the project to migrate successfully:

Peripheral	Connected Device	Teensyduino Driver	teens4-rs Driver
Ethernet (on-board)	DP83825i over RMII	NativeEthernet	?
SD card (built-in)	Generic microSD card over 4-bit SDIO	SD	?
NeoPixel Array	SK6812 over Single-Wire	OctoWS2811	?
I2C Display	SSD1305 over I2C	Adafruit_SSD1305	?

The ethernet interface driver is an absolute necessity, it needs to be able to communicate over UDP to another device on the network. This is something I don't think I would have the technical knowledge to accomplish on my own, especially given the drivers use of the RMII communication protocol and DMA's as a beginner to rust, so a driver that already exists would be pretty much a requirement. The SD card driver would be a nice to have, although any small-volume (~10KB) persistent storage mechanism could be a hold-over solution. The NeoPixel array driver is another nice to have and seems pretty simple on the surface until you look into the code where you find that it again utilizes DMA's so an off-the-shelf driver would be preferred. The display driver would be nice to have but I'm confident I could create the driver myself given access to an I2C bus and enough development time.

I've done a little bit of searching for some of these drivers/libraries but as a newbie it's really hard to understand which ones are meant for generic rust vs. embedded rust vs. teensy4 rust vs. specifically teensy4-rs. I'd love people's help finding which off-the-shelf repos I could use and which ones I would have to write from scratch. I'd be more than happy to help write some documentation for other beginners and test examples as I get some of these things working.

I can't wait to see the rust tooling around the Teensy 4(.1) become a viable replacement for Teensyduino and get more people writing memory-safe code for microcontrollers!

Thanks!

[mciantyre]

We're not as polished as what's available in the official Teensy ecosystem, but you shouldn't have to build everything from scratch.

Ethernet

imxrt-enet should work on the Teensy 4's MCU. When paired with smoltcp, you should be able to create UDP sockets and talk with your other devices. I've used this MAC driver with RMII, MII, and GMII PHYs, but not specifically that TI PHY.

I have a long-standing TODO to finish integration into imxrt-hal; see imxrt-rs/imxrt-hal#146. Once that's done, I'll make the driver available through the teensy4-bsp. If you start exploring without that integration, don't forget to check the MCU's ENET clocks, and to mux the pins.

SD card

imxrt-usdhc has been tested with 1 SD card on 1 board. With your help, we'll double that. Here's a demo. Again, if you start exploring on the Teensy 4, don't forget to check the USDHC clocks and pin mux.

NeoPixel array

Sorry, I've never worked with these parts. You could see if ws2812-flexio fits the bill. This uses a different peripheral than the official driver, which might affect the pins you're able to use.

I2C display

Try using the teensy4-bsp's LPI2C peripherals with one of these device driver crates. I didn't find one that precisely matched your part, but I wouldn't expect them to change that much. If nothing else, these could be an example for your own work.

[Nbelles]

This is exactly the kind of response I was looking for! Thank you for the detailed response and pointers to GitHub repos. I will definitely take a look through them in the coming days and see what I'm able to get working.

[tacertain]

Hey @Nbelles. I'm also new to Rust and trying to move some Teensyduino code over. Did you make progress on the SD card integration? Any gotchas for a newbie?

[Nbelles]

Sorry, I took a look at the SD card piece but realized it was going to be a bit more of an investment of time than I anticipated and ended up having to take a break from my project for a bit. It seemed as though there were a few pieces that have been implemented for other processors that haven’t been implemented for the teensy4 processor and would likely take some help from someone more knowledgeable than me.

Let me know if you have more time to take a look at it and make progress, I’d love to hear how far you get!