Turnigy 9x (Stock Firmware) - Unexpected throttle on startup

Mike

=)
Admin
Setup: Turnigy 9x tx/rx combo with stock firmware on the tx and a CC3D Copter Control flight controller.

Issue: After an unexpected burst of throttle that sent my copter into the ceiling in my house, I rebuilt and completed testing without props. During this testing, I determined that if I turned off the tx with the board still armed, then turned it back on, the tx would send about half throttle signal to the rx for a few seconds - even though the stick was at -100. This issue happened consistently every single time.

Other Reports: After looking all over the Internet, I was able to find only a single other person reporting the exact issue I was having. Being that a lot of people use this tx, I'm assuming this bug may only affect a handful of units.

Resolution: To resolve this issue, I reflashed with er9x firmware, which required modifying the tx with a solderless programming board from SmartieParts.

https://code.google.com/p/er9x/

http://www.smartieparts.com/shop/index.php?main_page=product_info&products_id=331

Lessons Learned:

1. Make it a habit to disarm your board immediately after a landing to avoid situations like this or even accidentally giving the copter throttle by brushing up against the sticks or setting down the tx on them.

2. After all of the modifications I did to this tx to make it adequate, I could have simply purchased a higher quality tx. Also, the 9x gimbals seem to be pretty poorly made and they don't sell replacements for them - only for the 9xr. So now, this tx is somewhat unusable. I've since purchased a 9xr to test out as my "cheap" tx, so we'll see how that goes.

3. Dont' test with props on indoors. But then again - maybe a flyaway is more dangerous? Maybe test outside and tie the copter to a heavy object to avoid a flyaway when testing.
 
Did you consider the other two popular firmwares? OpenTX is coming up behind ER, but "gruvin" is still popular too. If so, what made you select ER?

I just prepared to flash mine too. But I soldered the leads rather than buy the Smartie Parts board. I figured I can use the USBasp for other things, and frankly I wasn't impressed with the theory that you can align a board SO WELL than sticking four conductive pins down will consistently contact the right points! I just wasn't sold on that one.
Oddly, the (Smartie Parts) board contacts the 9x main board in four positions, while the solder-and-external-USBasp solution uses SIX contacts. I wonder which two it uses that the board does not (and why)? The soldering was pretty easy, but the connector they call for is supposedly supplied by Digi-key, but is unknown to any local supplier, so I'll adapt when my USBasp gets here, probably Monday or Tuesday. I also have 3S Lipos and a backlight kit due in Monday, so I'll crack the radio again middle of next week to finish everything.
 
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