PIN questions

[kjm]

A couple of PIN questions:

1. In the docs they say alt is the alternate fn for p = Pin('P10', mode=Pin.OUT, pull=None, alt=-1) I don't understand what that means? Could someone give me an example of how you might use alt?
2. I want to change multiple output pins simultaneously. There doesn't seem to be a way to group pins? Any suggestions?

[robert-hh]

@kjm
About pt1: You have to look into the ESP32 technical reference manual, section "IO_MUX Pad List". There is a table with the suitable functions of each Pin.
About pt 2: You use machine.mem32 to write directely to the GPIO output register. You can set the Pins to respective mode before. You will find the addresses of the output register in the ESP32 technical reference, chapter 4.12. Writing for instance a 1 to the respective position in register GPIO_OUT_W1TS_REG will set that bit to 1 without changing the other pins, wrting a 1 to GPIO_OUT_W1TS_REG will set that bit to 0. Writing a pattern to GPIO_OUT_REG will write that pattern to the set output pints. You can get the actual value. And you have to refer to the GPIO numbers, not the Pxx numbers.
Below is a sample script, not very efficient, but it works. The interesting line is line 22.

from machine import Pin, mem32

def write_multi(data, pin_list, init=False):
    if init:
        for pin in pin_list:
            Pin(pin[0], Pin.OUT)
    mask = 0
    value = 0
    if type(data) is int:
        for i in range(len(pin_list) - 1, -1, -1):
            pin = pin_list[i][1]
            mask |= 1 <<  pin
            value |= ((data & 1) << pin)
            data >>= 1
    else:
        for i in range(len(pin_list)):
            print(pin_list[i])
            pin = pin_list[i][1]
            mask |= 1 << pin
            value |= ((data[i] & 1) << pin)
    mask = 0xffffffff - mask
    mem32[0x3FF44004] = (mem32[0x3FF44004] & mask) | value

def run():
    init = True
    for n in range(8):
        write_multi(n, (("P9", 12), ("P10", 13), ("P11", 22)), init)
        init = False
    for n in range(8):
        write_multi((n >> 2, n >> 1, n), (("P9", 12), ("P10", 13), ("P11", 22)), init)

[kjm]

tnx Rob I'll try my luck