9x Full Mod DSM2/X
DSM2 / DSMX Module
This mod converts a FlySky module to a 6 channel Spektrum DSM2 & DSMX compatible module, using the internals from a Spektrum DX4e cheapie transmitter, so it can be used on a 9x transmitter running compatible firmware.
The mod is based on this thread: T9X mod to use Flysky module, Frysky module and DSMX module
Required for this mod:
- Spektrum DX4e (or DX5e) transmitter, for:
- DSM Module
- 3.3V Voltage Regulator (AZ1117 Series 3.3V 1A Low Dropout Linear Regulator in a SOT-223 package)
- 220uF 6.3V Electrolytic Radial Lead Capacitor
- 4K7 Ohm resistor
- 1N4001 Diode
- 150mm / 6" thin (30-32 AWG) wire, preferably in different colors
- Thin heat shrink tubing to cover solder joints
- FlySky transmitter module
- FrSky replacement module antenna lead
- FrSky replacement 2dB module antenna
NOTE: The DX4e can still be used as a flight simulator controller after the DSM module has been removed. In this case you would have to find a different source for the 220uF capacitor and the 3.3V voltage regulator.
First step is to remove the required components from the DX4e.
Open the DX4e by removing the 4 screws on the back of the transmitter as shown:
Remove the main PCB from the front half of the transmitter by taking out the 5 screws shown:
On the left side of the main PCB, locate the voltage regulator and the capacitor, then desolder them. This step can be omitted if you intend to use the DX4e for a flight simulator.
The capacitor is located on the other side of the PCB:
Next remove the transmitter module. The module is connected to the main PCB with 12 pins that will have to be desoldered. Use a desoldering pump or solder wick - this one may be challenging!
At this point you should have removed 3 components from the DX4e's main PCB:
Now we need to work on the FlySky module. Open the module by removing the 2 screws on the back and seperating the halves. The PCB should lift out easily:
Desolder the antenna coax from the PCB.
The antenna can then be removed from the module case by removing the screw (under the antenna coax) and digging out the hot glue. The antenna is not needed for this mod as we will be using a replacement FrSky antenna.
The 2 PCBs from the module now need to be seperated by desoldering the 7 pins connecting them. Use a desoldering pump or soldering wick.
This mod requires the module PCB with the button, although the button will be non-functional in the module:
We will be reusing the module connector and the 5V Voltage regulator:
If you also did the Telemetry mod on your transmitter using pin 2 & 5 on the module connector, isolate pin 2 on the module PCB by cutting the traces on both sides:
Solder the 1N4001 diode onto the PCB noting the orientation:
Bend the one leg of the diode (2nd hole) 90 degrees and leave about 5mm which will be used to solder other components:
Solder 30-40mm of wire to the legs of the 220uF capacitor removed from the DX4e. Be sure to cover the solder joints with heat shrink tubing:
Solder the wire connected to the NEG leg of the capacitor to the middle pin of the 78M05 5V Voltage Regulator:
- Prepare the 3.3V Voltage Regulator from the DX4e by bending up the middle pin and the big pin (both output 3.3V).
- Flip the PCB over and solder the left and right pins of the 3.3V voltage regulator to the module PCB.
Make sure nothing is touching except where it's supposed to!
Solder the 4K7 Ohm resistor between the bent diode leg and small middle output pin of the 3.3V voltage regulator:
Solder the POS leg of the 220uF capacitor to the small middle output pin of the 3.3V voltage regulator:
At this point it's a good idea to to test that you are getting 3.3V BEFORE connecting the DSM module. The module PCB can be plugged into the module connector on the 9x (as shown in the previous image) to test the 3.3V output. Turn on the transmitter and test for 3.3V with a multimeter between the small middle pin (or the big tab) and GND on the module PCB.
Solder the 3 wires (+3.3V, GND & PPM) that connect the module PCB to the DSM module:
The 3 wires should now be connected to the DSM module. There are several ways to do this, depending on how you decide to mount the DSM module in the module case. The wires can be soldered directly to the module or use a connector with appropriate pin spacing. The following picture shows how the wires are soldered directly to the DSM module:
The DSM module connected to the FlySky module PCB:
Last step on the module is to fit the replacement FrSky antenna lead.
- Trim the plastic ribs until the antenna connector freely slides into the module's antenna bay.
- Use the washer & nut supplied to screw it onto the module case:
Use a little bit of hot glue to secure the antenna connector:
- Connect the antenna lead to the DSM module with the U.FL connector.
- Install the FlySky PCB and the DSM module into the module case.
- Make sure the antenna lead is routed so that it doesn't get kinked.
- Close the module case using the 2 screws on the back.
- Screw on the antenna.
- As noted, the button on the FlySky module is not functional.
- Remember to select DSM2 as the protocol on the model setup screens
- To bind the module to a DSM receiver, hold the trainer switch like on a Spektrum transmitter.