docs update

README.md

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-# espnow-rclink-tx
+# EspNow RCLink Transmitter
+
+Designed for use in small short-range remote-controlled aircraft, vehicles and [ESP-FC](https://github.com/rtlopez/esp-fc) flight controller software.
+
+Simple implementation of external module with EspNow RcLink protocol. Just upload code to ESP32 module and connect to your transmitters JR bay.
+
+Module accepts `PPM` signal on `GPIO13` and transmits 8 RC channels.
+
+## Connection diagram
+
+![EspNow RcLink connections](/docs/img/espnow_rclink_tx_bb.png)
+
+> [!NOTE]
+> Keep eye on power consumption, linear voltage regulator might get hot. Switching regulator (step-down) is recommended if voltage drop is high.
+
+## Flashing
+
+1. Download and unzip selected firmware from [Releases Page](https://github.com/rtlopez/espnow-rclink-tx/releases)
+2. Visit [ESP Tool Website](https://espressif.github.io/esptool-js/)
+3. Click "Connect" and choose device port in dialog
+4. Add firmware file and set Flash Address to `0x00`
+5. Click "Program"
+6. After success power cycle board
+
+![EspNow RcLink Flashing](/docs/img/esptool-js-flash-connect.png)
+
+Your module is redy to use.
+
+## Using with ESP-FC
+
+To use [ESP-FC](https://github.com/rtlopez/esp-fc) as receiver just select `SPI Rx (e.g. built-in Rx)` as Receiver mode. Receiver provider doesn't matter here.
+
+![ESP-FC receiver](/docs/img/espfc_receiver.png)
+
+Transmitter and receiver binds automatically after power up, you don't need to do anything. Recomended startup procedure is:
+  1. turn on transmitter first
+  2. next power up receiver/flight controller