M2351: Integrate ESP8266 power on/off logic into ESP8266 driver main…

[ccli8]

Description

On the NuMaker-PFM-M2351 board, the RST pin of the on-board ESP8266 module is not connected. Instead, a GPIO PD_7 is used to power on/off the module. This PR tries to integrate the power on/off logic into ESP8266 driver mainline. It has the following purposes:

1. Application code can exempt from the power on/off logic and will get clear.

   ESP8266Interface esp(PD_1, PD_0, false, PD_3, PD_2, PD_7);
   

2. Support reset in ESP8266 driver

Related PR

This PR relies on #11288 for M2351 target renaming.

Pull request type

[ ] Fix
[ ] Refactor
[X] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Release Notes

[ciarmcom]

@ccli8, thank you for your changes.
@ARMmbed/mbed-os-ipcore @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

I'll wait for ipcore team to review but seeing TARGET_ in interface code does not look good to me.

[michalpasztamobica]

I admit, I also don't fully understand this PR.
The reset pin itself can be configured in mbed_app.json. Seems that this is clear, as I don't see it overriden in the PR's code.
Now, I infer from the code that the remaining difficulty is that the pin has different polarity that the ResetPin class assumes? @ccli8 , do you know if there could be some pull-up/pull-down issue on your board? I think, depending on the exact ESP device+shield combination you may need some external pull-up resistor, to get reset to work - I am not sure about this, but maybe @VeijoPesonen know more?

[ccli8]

Board circuit is not to change.

Without this PR, application needs to write ESP8266 initialization code like:

WiFiInterface *WiFiInterface::get_target_default_instance()
{
    static DigitalOut esp_pwr_off(PD_7, 1);     // Disable power to on-board ESP8266
    static ESP8266Interface esp(PD_1, PD_0, false, PD_3, PD_2, NC);

    esp_pwr_off = 1; // Disable power to on-board ESP8266
    wait_ms(2);
    esp_pwr_off = 0; // Enable power to on-board ESP8266
}

And there is no way for ESP8266 driver to re-power the ESP8266 module through ESP8266Interface::disconnect() when the ESP8266 module misbehaves.

But with this PR, application just needs to configure ESP8266 in mbed_app.json:

            "esp8266.rx"                                : "PD_1",
            "esp8266.tx"                                : "PD_0",
            
            "esp8266.rst"                               : "PD_7",
            
            "esp8266.rts"                               : "PD_3",
            "esp8266.cts"                               : "PD_2",
            
            "esp8266.provide-default"                   : true,
            

PD_7 is power on/off pin for the ESP8266 module, and does not connect to its reset pin (board circuit). This PR borrows the ESP8266Interface::ResetPin::rst_assert() and ESP8266Interface::ResetPin::rst_deassert() code to support reset via the PD_7 pin.

[michalpasztamobica]

If there is no way to alternate the logic elsewhere, then I suggest to add some kind of RST_PIN_POLARITY setting in mbed_lib.json, so that this can be configured per target in mbed_app.json.

EDIT: there is very similar case under discussion in #11302, where I gave a more detailed instructions. @ccli8 , please let us know if you understand the point of the changes and if you have any doubts on how to achieve them, feel free to ask.

[ccli8]

@michalpasztamobica OK. I will add RST_PIN_POLARITY like configuration into mbed_lib.json to substitute for the #if target code.

[ccli8]

Create #11331 to replace this one.

[ccli8]

Close via #11343