Revisions to SPI classes

[mikee47]

Refactor, tidy and implement SPIClass for ESP32.

External interfaces haven't changed but internal ones have.
Tested with ScreenTFT_ILI9340-ILI9341, SDCard and Radio_nRF24L01 samples.

bugfix: correct CPU multipler, should be 1M (was 10M)

Naming / comments / style

• Remove extraneous debug statement in setClock()
• Get rid of redundant/duplicate comments
• Don't repeat method name in brief
• Use cstdint types

SPI code revisions to simplify and improve performance

• SPISettings passed by reference. SPIClass no longer keeps a copy of these, no point.
• Clock register value is pre-calculated and stored in settings. Code simplified for readability.
• bugfix: exception (division by zero) raised in some cases, e.g. freq = 27M.
• BeginTransaction() and prepare() just set up registers anyway as there is now minimal overhead in doing this.

Implement SPIClass for Esp32

Has three available SPI modules:

• VSPI works reliably
• HSPI works with SPI display but not with SDCard (even at low clocks) but it does work with remapped pins (e.g. SPIClass(SpiBus::HSPI, SpiPins{18, 19, 23})). Suspect involvement with RTC/IO but as yet unable to pin this down.
• FSPI crashes: needs more work (it's shared with Flash).

[slaff]

Fix Esp32 code (not yet working - just copied Esp8266 version)

Just bought one of these LILYGO ESP32 watches. Hope to be able to run Sming on it soon :-)

[mikee47]

Re. #2171 (comment) I'll get this PR tested so we can merge it, then start on updating the HardwareSPI library with ESP32 support.

As for the Esp32 Arduino SPI interface I'm not sure what to do about that. Looking at the Esp32 arduino code it does the same thing as the Esp8266 stuff and just mucks about with hardware registers directly. It's generally a poor model (I don't use it).

[slaff]

@mikee47 Do you think you can add also I2C support for ESP32?

[mikee47]

@slaff I'll certainly take a look at I2C at some point. Hardware support for I2C on ESP32 warrants a separate HardwareI2C library, even more important to make that asynchronous given the slow bus speeds.

[slaff]

@mikee47 what is the status of this PR? Did you have a chance to test it on Esp32 device?

[mikee47]

@slaff Works fine on ESP8266, ESP32 is WIP

[mikee47]

@slaff OK ready for review/testing.

[slaff]

@kmihaylov can you try using this PR and one or two of your devices that use SPI?

[kmihaylov]

Wow too much activity on the SPI class. Should I wait a bit or give it a go?

[slaff]

Should I wait a bit or give it a go?

@kmihaylov Go for it. Please test both ESP8266 and ESP32.

[slaff]

@mikee47 PR #2188 is now merged. You can rebase on latest develop and check on your microcontrollers.