Richard J. Prinz

This post describes an easy and cheap way of adding a USB serial port to a Walkera RX2634H (QR Ladybird) or RX2635H (Hoten-X) RC quadcopter receiver board. This makes it very easy to update these controllers with new software (especially when using UP42)

The used USB to serial board uses a CP2102 from Silicon Labs. Such boards are cheap and easy available on platforms like ebay or amazon. The board is also very light (~2 gramms) so that it can be permanently installed on the receiver without impairing flight performance.

This post is part of a series:

1. Flashing new Firmware to Walkera RX/TX without UP02
2. Decrypting receiver firmware
3. Walkera receiver components
4. Hello World firmware for the RX2635H board
5. Serial port and external 16MHz oscillator
6. Using the ITG-3205 mems gyro
7. Walkera UP02 software clone: UP42
8. Walkera RX2635H as generic development board?
9. Walkera USB port (this post)
10. Walkera + Arduino = Walkino

The USB board is glued with double sided tape onto the bottom side of the receiver (the side where the CYPRES CYRF6936 wireless USB transceiver is located). In this case a RX2634H. Ensure that you use a non conductive double sided foam tape (e.g. from 3M) and that the whole bottom side of the converter board is covered with tape so that it is insulated from the receiver board. As there are no part on the bottom side of the converter and due to its size it fits perfectly on the receiver board.

Ground (GND), receive (RX), transmit (TX) and DTR (for automatically reseting the board) of the converter board are connected to the receiver as shown:

DTR is used to automatically reset the board when uploading new firmware with UP42. This omitts the need of disconnecting and connecting the battery to initiate the flash process.

Leave 3.3V and 5V on converter disconnected as the board is only powered when USB is connected and the receiver has its own power source (flight battery).