* new ESPNOWRadio driver

* refactored the examples/*/main.cpp modules, moving radio specifics to variants/*/target modules
* new Generic_ESPNOW_* target envs

variants/generic_espnow/platformio.ini

@@ -0,0 +1,83 @@
+
+; ----------- Generic ESP32-C3 ------------
+
+[Generic_ESPNOW]
+extends = esp32_base
+board = esp32-c3-devkitm-1
+;board = esp32-s3-devkitm-1
+build_flags =
+  ${esp32_base.build_flags}
+  -I variants/generic_espnow
+;  -D ESP32_CPU_FREQ=80
+  -D PIN_BOARD_SDA=-1
+  -D PIN_BOARD_SCL=-1
+;  -D P_LORA_TX_LED=8
+  -D PIN_USER_BTN=0
+;  -D ARDUINO_USB_MODE=1
+;  -D ARDUINO_USB_CDC_ON_BOOT=1
+;  -D ESPNOW_DEBUG_LOGGING=1
+;  -D MESH_PACKET_LOGGING=1
+;  -D MESH_DEBUG=1
+build_src_filter = ${esp32_base.build_src_filter}
+  +<helpers/esp32/ESPNowRadio.cpp>
+  +<../variants/generic_espnow>
+
+[env:Generic_ESPNOW_terminal_chat]
+extends = Generic_ESPNOW
+build_flags =
+  ${Generic_ESPNOW.build_flags}
+  -D MAX_CONTACTS=100
+  -D MAX_GROUP_CHANNELS=1
+build_src_filter = ${Generic_ESPNOW.build_src_filter}
+  +<../examples/simple_secure_chat/main.cpp>
+lib_deps =
+  ${Generic_ESPNOW.lib_deps}
+  densaugeo/base64 @ ~1.4.0
+
+[env:Generic_ESPNOW_repeater]
+extends = Generic_ESPNOW
+build_flags =
+  ${Generic_ESPNOW.build_flags}
+  -D ADVERT_NAME='"ESPNOW Repeater"'
+  -D ADVERT_LAT=-37.0
+  -D ADVERT_LON=145.0
+  -D ADMIN_PASSWORD='"password"'
+build_src_filter = ${Generic_ESPNOW.build_src_filter}
+  +<../examples/simple_repeater/main.cpp>
+lib_deps =
+  ${Generic_ESPNOW.lib_deps}
+  ${esp32_ota.lib_deps}
+  densaugeo/base64 @ ~1.4.0
+
+[env:Generic_ESPNOW_companion_radio_usb]
+extends = Generic_ESPNOW
+build_flags =
+  ${Generic_ESPNOW.build_flags}
+  -D MAX_CONTACTS=100
+  -D MAX_GROUP_CHANNELS=8
+;  -D ENABLE_PRIVATE_KEY_IMPORT=1
+;  -D ENABLE_PRIVATE_KEY_EXPORT=1
+; NOTE: DO NOT ENABLE -->  -D MESH_PACKET_LOGGING=1
+; NOTE: DO NOT ENABLE -->  -D MESH_DEBUG=1
+; NOTE: DO NOT ENABLE -->  -D ESPNOW_DEBUG_LOGGING=1
+build_src_filter = ${Generic_ESPNOW.build_src_filter}
+  +<../examples/companion_radio/main.cpp>
+lib_deps =
+  ${Generic_ESPNOW.lib_deps}
+  densaugeo/base64 @ ~1.4.0
+
+[env:Generic_ESPNOW_room_server]
+extends = Generic_ESPNOW
+build_flags =
+  ${Generic_ESPNOW.build_flags}
+  -D ADVERT_NAME='"Heltec Room"'
+  -D ADVERT_LAT=-37.0
+  -D ADVERT_LON=145.0
+  -D ADMIN_PASSWORD='"password"'
+  -D ROOM_PASSWORD='"hello"'
+build_src_filter = ${Generic_ESPNOW.build_src_filter}
+  +<../examples/simple_room_server/main.cpp>
+lib_deps =
+  ${Generic_ESPNOW.lib_deps}
+  ${esp32_ota.lib_deps}
+

variants/generic_espnow/target.cpp

@@ -0,0 +1,29 @@
+#include <Arduino.h>
+#include "target.h"
+#include <helpers/ArduinoHelpers.h>
+
+ESP32Board board;
+
+ESPNOWRadio radio_driver;
+
+bool radio_init() {
+  // NOTE: radio_driver.begin() is called by Dispatcher::begin(), so not needed here
+  return true;  // success
+}
+
+uint32_t radio_get_rng_seed() {
+  return millis() + radio_driver.intID();  // TODO: where to get some entropy?
+}
+
+void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr) {
+  // no-op
+}
+
+void radio_set_tx_power(uint8_t dbm) {
+  radio_driver.setTxPower(dbm);
+}
+
+mesh::LocalIdentity radio_new_identity() {
+  StdRNG  rng;  // TODO: need stronger True-RNG here
+  return mesh::LocalIdentity(&rng);  // create new random identity
+}

variants/generic_espnow/target.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <helpers/ESP32Board.h>
+#include <helpers/esp32/ESPNOWRadio.h>
+
+extern ESP32Board board;
+extern ESPNOWRadio radio_driver;
+
+bool radio_init();
+uint32_t radio_get_rng_seed();
+void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr);
+void radio_set_tx_power(uint8_t dbm);
+mesh::LocalIdentity radio_new_identity();