Help on making a new *_map.h file

[HubertBloom]

I'm trying to understand the flexibility (or limits of flexibility) of pin assignment when compiling for a custom board.

I've seen that in some versions of the map file the pin definitions are offset from other values. Does this mean that it is not possible to select any pin for any function?

For example in RP2040/boards/generic_map_8axis.h there is several examples of code like:

#define M3_STEP_PIN (STEP_PINS_BASE + 3)
#define M3_DIRECTION_PIN (Z_DIRECTION_PIN + 1)
#define M3_LIMIT_PIN (Z_LIMIT_PIN + 1)

One pin is set to another pin plus an offset. Why is it like this? What is the significance of the offset? Is it not possible to just pick a pin and put a literal number in the #define? And change the number according to the board layout?

[terjeio]

Does this mean that it is not possible to select any pin for any function?

No.

One pin is set to another pin plus an offset. Why is it like this?

Mainly to not exhaust PIO state machines. A single state machine can handle one or many pins - but only if they are consecutive.

Is it not possible to just pick a pin and put a literal number in the #define? And change the number according to the board layout?

It is possible, as long as you do not exhaust PIO state machines for controlling the stepper pins. The RP2040 has eight, one is used for the main stepper timer. Depending on the configuration others might be used for no-stepper related stuff.

See the RP2040 datasheet, Chapter 3 (3.5.6), for more.

[HubertBloom]

Thank you. That’s a useful steer.

Are there any ‘how to’ or tutorial type articles on designing and compiling for a new board?
(I have some picoCNC boards but eventually will need a custom board)

[terjeio]

Are there any ‘how to’ or tutorial type articles on designing and compiling for a new board?

Not that I know of - I have not written any.

If the new board is for private use only create a new map file named my_machine_map.h in the boards directory, copy the closest matching existing one to it if you do not want to start from scratch, and enable it in my_machine.h.

If the design is published and/or commercially available it has to be given a name and added to the boards directory, my_machine.h and driver.h. And optionally to driver.json - used by the Web Builder.