First things first great site i have found it very helpful in my quest to build my own cockpit based on the 737.

I am having an issue with my stepper motors 28BJY-48 type converted as per the instructions and connected to the A3967 driver board wired as per instruction. I am using an Aduino Mega 2560 R3 as my master board with the simvim firmware and the Uno board as my slave also with the firmware for stepper. Both boards connected via TX and RX as per instruction, both boards earthed master board is connected to PC USB and the slave a dedicated 5v via USB phone charger. stepper DIR into pin 13 for both steppers DIR's are linked and the steps into pin 10&11, using AT_Motor and these lines in the Data file.

G10 AT_MOTOR s=3
G11 AT_MOTOR s=3

I can get the steppers to move when AT is engaged but only in one direction. In the Calibration tool no mater which arrow i click  it rotates in same direction i am using xplane 11 with 737 Zibo mod.

I did notice only last night that the TX and RX on the Slave are not flashing, i do have flashing RX on the master board i have ordered a new uno which should be here tomorrow in case it is a bad board. can you offer any further advise or suggestions on the steppers rotating in one direction or point out what i could be missing. 

any help you can offer would be very much appreciated.

Thanks in advance 


Mar 8 in Output - Stepper by

1 Answer

Why do you have two outputs assigned to the same parameter?
Do you have a zero-position switch?

The Rx/Tx on the slave should NOT be flashing at all.
They are working only when serial-USB driver chip is used (via USB connector).
Mar 9 by
Hi Vlad many thanks for getting back so quick, sorry the S3 was a copy and paste error.

I have two stepper motors one for the left throttle and one for the right

when you mentioned a zero position sensor would that be a mechanical Micro switch at the idle position for each throttle left and right, and thanks for clearing up the RX And TX i have a new board delivered today so i will keep as a spare

Adding the micro switch as a zero position sensor would that then enable me to control the steppers using the left and right buttons in the calibration tool because at the moment it does not matter which i choose the steppers only turn one way. they both work independently using just the 10k pots but not with AT and steppers

this is the one issue that is stopping my throttle build dead in the water any further help you can give thanks. it is getting to the pull the hair out time

Appreciate your help Thanks

Hi Vlad,

I have managed to get the steppers moving in the right direction with both arrow buttons on the config tool when i am flying in xplane 11 with AT on the stepper is not moving i can see the throttles moving on screen according to the adjusted air speed what am i missing here almost working
Have you calibrated the stepper ?
Hi Vlad

I think i have can you advise what data ref the A/T 737 is reading from to give an output to the stepper is it N1 or N2  EGT  FF or IAS on the MCP
The SimVim custom parameter "AT_MOTOR" has value range from 0.0  to 1.0