How to understand Pin.ALT

[livius]

Hi,

what does it mean if i write something like this?

Pin('GP16', mode=Pin.ALT, pull=Pin.PULL_DOWN)

i see this in
https://github.com/danicampora/wipy-WS2812/blob/master/ws2812.py

[mmarkvoort]

@livius

Ah, I understand what you mean.
Don't know this either...

But I think it is indeed for WiPy 1.0
On this image it says GP16 is MOSI.
I found the image according to this forum post.

[livius]

@mmarkvoort

near to understand but looking at maping rules:

	LED/USB
RST		5V
P0 - G2		GND
P1 - G1		3,3V
P2 - G23	P23 - G10
P3 - G24	P22 - G9
P4 - G11	P21 - G8
CLK - G12	P20 - G7
MOSI - G13	P19 - G6
MISO - G14	P18 - G30
P8 - G15	P17 - G31
P9 - G16	P16 - G3
P10 - G17	P15 - G0
P11 - G22	P14 - G4
P12 - G28	P13 - G5

and description about SPI default pins:

# this uses the SPI default pins for CLK, MOSI and MISO (``P10``, ``P11`` and ``P12``)

i do not understand why GP16? not e.g. GP17?

Pin('GP16', mode=Pin.ALT, pull=Pin.PULL_DOWN)

GP16 = P9 which is not default pin for SPI
or maybe this driver is not for Wipy2 only Wipi1.0
if this is true then now i am back understand this clearly :)

[mmarkvoort]

@livius

I found this on the docs.micropython website:

The Pin class allows to set an alternate function for a particular pin, but it does not specify any further operations on such a pin. Pins configured in alternate-function mode are usually not used as GPIO but are instead driven by other hardware peripherals.

See here for more information.