i hacked it at last!!!

[Awesome-Sauce RC]

ok so i thought i had to share this and show it can be done as my wife never seems to understand my satisfaction i get when conquering a project and just gives me "the look" like im a crazy person lol.

i recently had to buy a new transmitter and reciever as my old one died so being a long time spektrum guy i got the dx3e, if i wasnt on such a tight budget then i would have splashed out on the dx4s but that would probably end with some choice words from the wife.

after buying the radio i then remembered that the aux channel, as great as it was being able to select between 2p 3p or linear still would not work like i needed in a true 3p mode so i decided to tear it apart and investigate further as so many have done.

so after spending a little bit of time probing with the multimeter and following pcb traces i found that the two switches both go to one pin on the microcontroller that spektrum used (a microchip pic).

the switch input to the chip rests high at 3.3v when neither switch has been pushed

each of the two switches pulls the input down to ground via a different resistor value when pushed which gives the microcontroller a different analogue to digital conversion value so it knows which switch you have pushed and what direction it should move in.

pushing the up switch pulls the input to ground via a 10k 1% resistor

pushing the down switch pulls the input to ground via a 5.6k 1% resistor

after finding out what i needed to know i hooked some wires up to both sides of the switches on the back of the circuit board and set up a few resistors and diodes on my breadboard and put some basic code on one of my microcontrollers on the board to read the different ADC values each switch gives when pushed.

after getting that info i then knocked up some simple code to monitor the switch and wait until it saw either of these values with a little bit of offset to ensure that it always saw what was happening with the switches and when to do what it needed to.

after some debugging and fine tuning i had the short and simple code done and just had to design and etch a small pcb and then populate it with some smd components and then hook it up.

the most tedious part was tapping into the onboard 3.3v regulator on the dx3e pcb as i had to run my board at the same voltage to ensure there were no problems between the two

the end result was very pleasing and i now have the ability to use the aux switch in the original spektrum styles including the non true 3p setting and then by flipping a switch i can have the 3p always return to centre as soon as i release either the up or down button.

if i use it in 2p setting i can also have the servo auto return to a low/high setting when the switch is released if i were to use it with a reverse module for example like i had in my savage x so it would hold reverse until the switch is released then revert the tranny back to forward.

i have to admit there were a few times i thought i would have to give up on this and almost admitted defeat a few times but somehow managed to succeed.

a vid of the dx3e torn apart and initial first test

https://www.youtube.com/watch?v=IKF2NHM0rk0

all reassembled and working

https://www.youtube.com/watch?v=2Nu6O_IcRaE



thanks for reading through my ramblings


tony

[Awesome-Sauce RC]

tapping into the onboard regulator for 3.3v for my hack board, i added a dab of hot glue over the connection after



module all hooked up to both switches,and a generous amount of hot glue again



the module is now buried behind the charging jack not really visible and all the wires are tidied/taped out of the way



everything finally put back together and looking normal again,well except for the addition of the new mode selector switch on the front



now its all done as far as i can tell after trawling around online this is the only true 3p DX3E

[6sharky9]

Should start buying up used radios and doing the mod then sell them...Get a vendors star

[Epcampau]

Pretty slick little idea. I love it. Great job my man. I may have to give a crack at this with my wife's radio

[wings_of_fire]

Originally Posted by Epcampau

I may have to give a crack at this with my wife's radio

Invitation for war? ..

[Charlie-III]

tony g, nice job and great write-up.

This is a little more than a "hack", nice just the same.

[crazy nick]

If I send mine to you can you make it "shoot freakin lazer beams" lol
I wish I had the knowledge to even attempt that. Awesome work!

[boosted4lyf]

Very cool back when they first came out we started replacing the 3rd ch switches with the extremely small momentary switches in Different spots

DX3E dig switch for BEAU

[Awesome-Sauce RC]

Originally Posted by crazy nick

If I send mine to you can you make it "shoot freakin lazer beams" lol

just having issues getting it to target opponent rc'ers lol

and i know how annoying that switch being at the rear is, i had noticed people moving it onto the grip so it was easier to use the thumb to control, definately was not a bright spark moment for spektrum when they made it but im guessing they learned from it now they have moved its position on some of the DX3 series.

thanks for the comments guys, it makes these crazy ideas worthwhile especially when i dont get a pat on the back from the wife as she doesnt understand why im so happy with accomplishing things like this lol