Is there softSPI available on pyb?

[Meekdai]

I have an application that needs to use multi-channel SPI. The micropython version I am using is v1.11, so machine.SoftSPI cannot be used.
Is there softSPI available on pyb? If not, is it possible to port the Arduino library (SoftSPI) to micropython?

[robert-hh]

The STM32 port for PyBoard support machine.SoftSPI, like most of the MicroPython ports.

[robert-hh]

If speed does not matter, it's pretty easy to implement SPI with Python. It's just a little bit of bit-banging.

[Meekdai]

I found that micropython v1.11 can use soft SPI by configured to -1. This is not introduced in the document. I found this hidden function after checking the source code, haha

spi = machine.SPI(-1,sck=sck,miso=miso,mosi=mosi,phase=phase,polarity=polarity)
spi.write_readinto(data.to_bytes(1,'big'),rdata)

[rkompass]

Here for example it was documented:

classmachine.SPI(id, ...)
Construct an SPI object on the given bus, id. Values of id depend on a particular port and its hardware. Values 0, 1, etc. are commonly used to select hardware SPI block #0, #1, etc. Value -1 can be used for bitbanging (software) implementation of SPI (if supported by a port).

This was changed in later versions. Nice that you found it yourself. How ?.. doesn't matter in the end :-)

[Meekdai]

I found the method in the following source code.

micropython/extmod/machine_spi.c

Lines 48 to 63 in 6f75c4f

	if (n_args > 0) {
	if (args[0] != MP_OBJ_NEW_SMALL_INT(-1)) {
	#if defined(MICROPY_PY_MACHINE_SPI_MAKE_NEW)
	// dispatch to port-specific constructor
	extern mp_obj_t MICROPY_PY_MACHINE_SPI_MAKE_NEW(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args);
	return MICROPY_PY_MACHINE_SPI_MAKE_NEW(type, n_args, n_kw, args);
	#else
	mp_raise_ValueError("invalid SPI peripheral");
	#endif
	}
	--n_args;
	++args;
	}
	// software SPI
	return mp_machine_soft_spi_make_new(type, n_args, n_kw, args);

[jimmo]

@Meekdai It is in the documentation, you just have to look at the v1.11 documentation: https://docs.micropython.org/en/v1.11/library/machine.SPI.html#machine.SPI
We removed it from the docs when machine.SoftSPI was introduced, but the functionality remains for backwards-compatibility.

I strongly recommend updating to v1.21. There should be very few breaking changes (and possibly none at all).