Richard J. Prinz

After playing around with analyzing how the firmware update process for a Walkera Hoten-X receiver (RX2635H) works and how this firmware is secured with a simple encryption method it’s now time to analyze the receiver hardware. So that it meight be possible to develop a custom firmware for this receiver.

This post is part of a series

1. Flashing new Firmware to Walkera RX/TX without UP02
2. Decrypting receiver firmware
3. Receiver hardware analysis (this post)
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
10. Walkera + Arduino = Walkino

The used receiver is a Walkera RX2635H used in the Hoten-X quadcopter. Other Walkera receivers are more or less the same (e.g. the RX2634 used in the QR Ladybird). In a very small space there is everything available what a standard quadcopter needs:

• a CPU; an ATMEL XMEGA32 AU4
• a 3 axis accelerometer; a FREESCALE MMA8452
• a 3 axis MEMS gyro; a INVENSENSE ITG-3205
• a wireless USB transceiver; a CYPRES CYRF6936
• 5V and 3V power stabilizers
• LED’s, one on the receiver itself and 4 via connectors on the copter case
• some passive components like resistors etc.

Where possible I have added the reference manual for each part. Except for the 3V power regulator with the SMD marking JJ=T08. It seems to be a RICHTEK company LDO part but it was not possible to determine the correct part.

The RX2635H das NOT contain motor drivers (ESC). As the Hoten-X is a larger model (compared to the QR Ladybird) there is a separate motor driver board used (X-Z-15; WST-16A4). On the Ladybird receiver (RX2634) they are included on the receiver board.

The following images describe each component. On the connectors the pins are labeled either with power (5V, GND etc.) or with their XMEGA port number.

Click on a picture for a larger view and more details.