SBUS - START BYTE HELP

Electronic projects that are either related to the firmwares for the 9x, or simply great for radio control applications.
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QuadRaf7
Posts: 1
Joined: Thu Dec 29, 2016 12:21 am
Country: United States

SBUS - START BYTE HELP

Post by QuadRaf7 » Thu Dec 29, 2016 4:21 am

Hi all,

I’m working on my newfound hobby where I’m building a quadcopter from scratch minus the controller and receiver. I'm now on the flight controller part. I’ve spent my holiday week working on writing code for the SBUS signal and am successfully reading all 8 channels without of packet loss. Microcontroller is a PIC33f possibly going to a PIC32.

I was wondering if anyone knows why the SBUS signal I’m receiving from my R2008SB is giving me a different start byte every other data frame. The start byte of the first frame comes out of the uart as 0x0F (to be expected) and the start byte of the second frame is 0x8F. I looked at my scope and the data was changing from frame to frame. Why is there a start bit of 0x8F on every other frame? Is this normal? I have attached scope shot of both frames. All channel data is identical other than the start bits.

I'm new to RC stuff.

Thanks!

FRAME#1 (0x0F)
Image

FRAME#2 (0x8F)
Image

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