ESP8266 - Allow `network.STA_IF` to `connect` on specific channel

[JayFoxRox]

Same request as in https://forum.micropython.org/viewtopic.php?f=16&t=12065
Also see https://www.bakke.online/index.php/2017/06/24/esp8266-wifi-power-reduction-avoiding-network-scan/

I'd also like to do this for power saving on a battery powered device.

I believe micropython isn't able to do this yet, because it's missing from connect:

(call does not allow channel as kwarg)

micropython/ports/esp8266/modnetwork.c

Lines 111 to 117 in 89b3207

	STATIC mp_obj_t esp_connect(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
	enum { ARG_ssid, ARG_key, ARG_bssid };
	static const mp_arg_t allowed_args[] = {
	{ MP_QSTR_, MP_ARG_OBJ, {.u_obj = mp_const_none} },
	{ MP_QSTR_, MP_ARG_OBJ, {.u_obj = mp_const_none} },
	{ MP_QSTR_bssid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_none} },
	};

Additionally, it's also not possible to set this from esp_config:

(setter only for AP, not STA):

micropython/ports/esp8266/modnetwork.c

Lines 395 to 399 in 89b3207

	case MP_QSTR_channel: {
	req_if = SOFTAP_IF;
	cfg.ap.channel = mp_obj_get_int(kwargs->table[i].value);
	break;
	}

(getter only for AP, not STA):

micropython/ports/esp8266/modnetwork.c

Lines 465 to 468 in 89b3207

	case MP_QSTR_channel:
	req_if = SOFTAP_IF;
	val = MP_OBJ_NEW_SMALL_INT(cfg.ap.channel);
	break;

[mmliam]

I would like to add my support to adding STAObj.config('channel=nn') to the ESP8266 build. Having the ability to fix a channel reduces connection time. This is particularly significant for one-off connects when waking from deep-sleep, or power-down. Currently the only way to fix the STA channel for an ESP8266 is to first create an AP object, set the AP channel, then create a STA object. Because there is only one radio the STA object utilizes the fixed channel.

The STA channel fixing feature already exists for the ESP32; perhaps the ESP32 build code, with modification as necessary, could be ported to the ESP8266 build.

[agatti]

The thing is, it looks like this cannot be done with the SDK being used by MicroPython - I needed this some time ago as well.

The channel field in struct station_config is not present in the ESP Open SDK the MicroPython port targets, while it appears in recent NONOS SDK releases from Espressif. No idea how far back this goes (it's been in maintenance mode for quite some time now, though).

Is there any interest in migrating the 8266 port to the official SDK at this point (and thus allowing use of recent compilers too)?