Implementing FTDI for Firmware Resuscitation

In instances where traditional firmware update methods like Betaflight Passthrough or Wi-Fi encounter disruptions, leading to receivers being rendered inoperative with their bootloaders damaged, the utility of an FTDI programmer for UART flashing becomes indispensable. This alternative proves crucial when you're without a flight controller or Wi-Fi access, providing universal support for ELRS receivers across the 2.4GHz and 900MHz spectrums without relying on proprietary software.


Essential Equipment

Central to this technique is the use of a USB to serial adaptor, known as an FTDI Programmer. The Radiomaster USB UART Flasher is highlighted for its specific utility in this context. While BetaFPV offers a comparable device, the ExpressLRS Recovery Dongle, the guidance provided herein applies to the Radiomaster variant but is generally suitable for use with devices from other manufacturers.

A generic FTDI programmer is an economical alternative, though it may forego some user-friendly features such as spring-loaded pins that enable direct, solder-free connections. The operation hinges on linking four crucial pins: RX, TX, VCC (5V), and GND (ground), with the RX and TX pins serving the purpose of data exchange.

Step 1 – Preparing the FTDI Dongle

Initiate by pinpointing the COM Port displayed in the ExpressLRS Configurator following the connection of the FTDI dongle to your computer. If a new COM port does not appear, you may need to install the cp2102usb driver.

Step 2 – Linking the Receiver with the FTDI Dongle

Activating the receiver's boot mode is a prerequisite for the FTDI update procedure whether you are using 1900KV brushless motor2450KV brushless motor11000KV brushless motor or 2004 Brushless Motor.

Typically, this requires pressing and holding the boot button on the receiver while it is being connected to the FTDI Dongle (the button can be released once the LED illuminates). In some cases, creating a temporary solder bridge may be necessary instead of a button press (which should be removed following the flashing operation).

While holding the boot button, connect the receiver to the FTDI Dongle adhering to the following configuration:

  • VCC to 5V
  • GND to ground
  • TX to RX
  • RX to TX

For the majority of ExpressLRS receivers, the 5V option is recommended. The Radiomaster UART Flasher is provided with a cable harness for facilitating connections to receivers without solder pads.

When the receiver's LED illuminates continuously, it signifies that it is in boot mode and ready for the firmware flashing process.

Step 3 – Setting Up Through ExpressLRS Configurator

Proceed with the standard configuration steps in the ExpressLRS Configurator, selecting the appropriate firmware version, device category, and the specific model of the receiver. Make sure the UART flash method is chosen. Adjust any other preferences accordingly and double-check the COM port for your FTDI programmer.

Step 4 – Initiating the Firmware Update

Click on ‘Build & Flash’ to begin the firmware updating process. Upon successful completion, the receiver can be disconnected from the FTDI dongle.

Wrapping Up

Becoming adept at FTDI-based firmware updates is invaluable, especially when confronted with difficulties using conventional update methods. This guide aims to provide a structured and straightforward approach to rejuvenating and updating your ELRS RX using an FTDI programmer, such as the specified Radiomaster USB UART Flasher, potentially saving your device from being discarded. Careful attention to your connection setup and configuration choices is essential for a seamless update process.

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