How to share GPIO between two SPI buses, or simple GPIO and SPI?

[yanshay]

I'm developing on a device with a limited number of GPIO's available.
I'm left with single GPIO free and the rest are used by a SPI device.
I want to add another device which requires two GPIO's and there are two ways to use it, either just using GPIO 'bit banging', or some hack to use another SPI with those pins (it's not really a SPI device but that technique seem to work).

I don't need both devices together, and I know when to switch between them.

I assume that when the SPI device takes over the GPIO, even if I unsafely get access to the GPIO, setting it to high/low, won't work, right? Because the ESP32 internally gave the control over the GPIO to the SPI.

If my assumption is correct, what's the proper way to give the SPI a GPIO, take it away, then give back?
Unsafe options are also acceptable in this case, since I'm just out of GPIO's.
Maybe control the esp32 behind the 'Rust scenes' in such case?

[Dominaezzz]

I assume that when the SPI device takes over the GPIO, even if I unsafely get access to the GPIO, setting it to high/low, won't work, right?

Yes (it won't work) for output pins, no for input pins like MISO.

If my assumption is correct, what's the proper way to give the SPI a GPIO, take it away, then give back?

The proper way would be to drop the spi driver.
The hack would be to tinker with the IO_MUX registers to borrow from the spi driver.

[Dominaezzz]

I'm guessing you've already used up the gpio expander on it? 😄

[yanshay]

You mean this?

I have still one GPIO available, looking for an additional one.

There's also the RS485, but I'm not sure about the voltage in those pins, do you happen to know how it functions?

[Dominaezzz]

do you happen to know how it functions?

Not really, but my guess is you can just use it like any other pin

[yanshay]

The RS485 don't behave like other pins, both in terms of voltage and behavior, they are differential, only one can really be controlled independently and only 2.7V. Maybe usable, but might cause issues.

GPIO0 is used by the display already.

I can't find the GPIO numbers for the TX/RX - I tried the common GPIO numbers for TXD/RXD, don't know if that's the same in all ESP32 of 3,1,16,17 - none worked.

Then I saw the GND is defined as GPIO14, which is also GPIO14 of EXT_IO5, so seems there's a mistake in the document, they probably copy/pasted the table and forgot to remove that row.

So my only option is if I can find the TX/RX GPIO, any way to find that? I tried all pins that are not assigned and neither work. Maybe esp-hal takes over that in some way for logging so I don't see it? though I'm connected through USB but maybe some initialization takes over?

[Dominaezzz]

So my only option is if I can find the TX/RX GPIO, any way to find that?

You mean you don't know the GPIO numbers?