Flipdot-display/src/esp32/nano_flash_bridge.h

#pragma once

#include <Arduino.h>
#include <WiFi.h>

// WiFi to serial bridge for flashing the Nano from the PC (pio run -e nano_ota -t upload).
//
// The uploader (tools/nano_net_upload.py) connects and first sends one line:
//   FLASH <baud>\n
// with the baud rate of the Nano's bootloader (57600 old bootloader, 115200 Optiboot).
// onStart(baud) then restarts the Nano into its bootloader, the bridge answers "OK\n",
// and from then on bytes are copied between the TCP connection and the Nano's serial port
// until the client disconnects or is idle too long. onEnd() is then called.
class NanoFlashBridge
{
public:
	NanoFlashBridge(uint16_t port, HardwareSerial &serial, void (*onStart)(uint32_t baud), void (*onEnd)());

	void begin();

	// Call from loop(). Returns true while a flash session is running; the caller must not
	// send anything to the Nano then.
	bool handle();

private:
	// Max wait for the FLASH line after connecting
	static const uint32_t HEADER_TIMEOUT = 2000;
	// Give up when no data moves in either direction for this long
	static const uint32_t IDLE_TIMEOUT = 10000;

	WiFiServer _server;
	WiFiClient _client;
	HardwareSerial &_serial;
	void (*_onStart)(uint32_t baud);
	void (*_onEnd)();
	bool _active = false;
	uint32_t _last_activity = 0;

	uint32_t _readHeader(WiFiClient &client);
	void _end();
};