[FR] Add Drive Strength parameter to GPIO boot state config

[TD-er]

Olimex has reported some issue with the clock pin of their GateWay board: espressif/arduino-esp32#9623

This mentions the drive strength of a GPIO pin.

After some searching, I found these 2 posts describing the actual max. current for sourcing and sinking a GPIO pin per drive strength.
https://esp32.com/viewtopic.php?p=25550#p25550

The measurements were made with the following resistances: infinite, 2kΩ, 1kΩ, 470Ω, 220Ω, 150Ω, 100Ω, 47Ω and 0Ω. But for strengths 2 and 3 the minimum resistance was 100Ω.

By measuring into a capacitor, I can confirm that the source and sink current limits for drive strength 2 are about 40mA and for drive strength 3 they are about 80mA. Actually source current limits are a little higher than the sink current limits.

The drive capabilities of the digital-to-analogue converters are very different.

The post below also has a lot of hard to find information on which pin is connected to which power domain:

There are three "power domains" on the chip, i.e. three separate power input sections.
Domain VDD3P3_CPU in on pin 37 (NOT GPIO 37) supplies power to GPIO5; GPIO18; GPIO23; GPIO19; GPIO22; GPIO3; GPIO1; and GPIO21.
This domain can SOURCE up to 40mA and SINK up to 28mA on STRENGTH 3

Domain VDD3P3_RTC in on pin 19 (NOT GPIO 19) supplies power to GPIO36; GPIO37; GPIO38; GPIO39 ; GPIO34; GPIO35; GPIO32; GPIO33; GPIO25; GPIO26; GPIO27;GPIO14; GPIO12; GPIO13; GPIO15; GPIO2; GPIO0; and GPIO4.
Remember GPIO34..GPIO39 are inputs only, so cannot be used to source or sink current meaningfully.
This domain can SOURCE 40mA and SINK up to 28mA on STRENGTH 3

Domain VDD_SDIO in on pin 26 (NOT GPIO 26) is a special bidirectional power pin which can be driven by 3.3V externally, route VDD3P3_RTC via an internal network, or supply 1.8V via a LDO regulator. The LDO regulator can only supply 40mA. If using power through VDD3P3_RTC, the internal network will cause a voltage drop; the higher the current drawn, the more voltage will be lost in the chip and more heat generated.
Domain VDD_SDIO supplies power to GPIO16; GPIO17; GPIO9; GPIO10; GPIO11; GPIO6; GPIO7; and GPIO8
This domain can SOURCE up to 20mA and SINK up to 28mA on STRENGTH 3 (Remember the 40mA total limit at 1.8V)

The sum of all the I/O current may not exceed 1200mA

And as a bonus hard-to-find figure, the internal pull-up and pull-down resistors are 45kOhms each.