teensy4-pins: add MicroMod pins

[cstrahan]

This adds the pins for the Teensy MicroMod.

I got the Pin# to Pad mapping from here: https://github.com/PaulStoffregen/cores/blob/2dbb6f6c58f3d8e1272286daba3f3b094893c5b3/teensy4/core_pins.h#L1209-L1775

And I compiled the list of alternative functions (for the doc comment) by referencing the manual.

(Thanks for all your work on the Teensy-related and imxrt crates!)

[mciantyre]

bors try

Looks great, thanks for adding this! I double-checked the pinouts and alternate functions.

I only recently learned about this board, so I was curious about the pin names. It looks like "pins" represent identifiers for processor pads, and they associate to what's available on the Teensy 4.0 and 4.1 board. Pins do not represent the pinout on the M.2 edge connector. For example, what we call pin 19 is broken out to the M.2 connector's bottom edge, pin 14.

The MicroMode pinout table explains all of this. This is all OK with me. If users prefer identifying pins by the M.2 edge connector, we could support that at a later time.

[bors]

try

Build failed:

• format

[mciantyre]

Note that #86 applies here, too. There seems to be more flash available on this board. But for the purposes of building a firmware image and defining the FCB, we pretend that we only have Teensy 4.0 flash capacity.

[mciantyre]

bors try

[cstrahan]

Pins do not represent the pinout on the M.2 edge connector. For example, what we call pin 19 is broken out to the M.2 connector's bottom edge, pin 14.

True -- I probably should have mentioned that. I'm currently taking a stab at porting some Arduino code over to Rust -- this library that uses DMA+FlexIO to implement a parallel IO interface to ILI948x LCD controllers (the MicroMod breaks out just enough contiguous FlexIO pins to make it work): https://github.com/david-res/ILI948x_t4_mm

The end goal is to wire that up with Slint and see how well it performs.

In my use case, being able to think of pins in terms of their Arduino counterpart is most convenient, but if you're working on a bespoke carrier board for the MicroMod and have no existing Arduino code in mind, you probably want to work with the MicroMod's M.2 pin numbers. 🤔

[bors]

try

Timed out.

[mciantyre]

Sounds like an awesome project. Reach out if you hit issues or have questions.

I'll release this in the 0.4 teensy4-bsp series later today.