esp32: fix pullup/pulldown on RTC GPIO pins

[pottekkat]

Fixes #3477

Issue

Pins with RTC function ignore the IO_MUX_GPIO0_FUN_WPU and IO_MUX_GPIO0_FUN_WPD bits, so PinInputPullup and PinInputPulldown did nothing.

The issue is that these pins (with RTC function, see ESP32 TRM table 6.11-1) have their pull configuration controlled instead by the RTC_IO registers.

Fix

The Pin.Configure function now calls configureRTCPull to set RUE and RDE (pullup and pulldown, respectively) bits in RTC_IO mapping the GPIO to RTC as shown in table 6.11-1 in the TRM shared above and also mirroring ESP-IDF esp_hal_gpio/esp32/rtc_io_periph.c#L57.

Testing

Tested on an ESP32 development board (exact model) by configuring pullup and then pulldown with nothing connected and confirmed the level through Pin.Get and also by measuring the voltage.

You can use the test script referenced in the original issue #3477 to validate the fix. Or something like this that checks all pins with this issue:

package main

import (
	"machine"
	"time"
)

// 22 is a non-RTC control pin.
var pins = []machine.Pin{22, 4, 12, 13, 14, 15, 25, 26, 27, 32, 33}

func read(p machine.Pin, mode machine.PinMode) bool {
	p.Configure(machine.PinConfig{Mode: mode})
	time.Sleep(20 * time.Millisecond)
	return p.Get()
}

func main() {
	time.Sleep(2 * time.Second)
	for {
		println("pin pullup pulldown pass")
		pass := 0
		for _, p := range pins {
			up := read(p, machine.PinInputPullup)
			down := read(p, machine.PinInputPulldown)
			ok := up && !down
			if ok {
				pass++
			}
			println(int(p), up, down, ok)
		}
		println("passed", pass, "of", len(pins))
		println()
		time.Sleep(3 * time.Second)
	}
}

[dgryski]

@deadprogram